Effect of Grain Sorghum Hybrid on In Vitro Rate of Starch Disappearance and Finishing Performance of Ruminants' T. J. Wester, S. M. Gramlich2, R. A. Britton3, and R. A. Stock Department of Animal Science, University of Nebraska, Lincoln 68583-0908
Hybrid A (fastest IVSD) was 9.0% faster than that of steers fed Hybrid D (slowest IVSD; 1.33 vs 1.22 kg, P = .06). Gain:feed ratio was positively correlated with IVSD across all treatments (R2= .94). Hybrids A and D, another Hybrid, Al, and a birdresistant hybrid (BR) were fed for 85 d to finishing lambs h e a n initial BW of 28 kg). Lambs fed Hybrid A gained more efficiently (gain:feed) than those fed BR or A1 (.210 vs .188 and .184, P c .05), and those fed D were intermediate (2001. Performance of sheep fed A l , with the fastest IVSD, and those fed BR, with the lowest IVSD, were similar, suggesting that factors other than IVSD affected lamb performance. Our data indicate that rate of grain sorghum starch digestion may influence feeding value of grain sorghum fed to cattle.
Key Words: Sorghum, Starch, In Vitro Digestibility, Sheep, Beef Cattle
J. Anim. Sci. 1992. 70:2866-2876
Introduction As the major component of cereal grains, starch is the primary dietary energy source for the beef feedlot industry. Ruminal starch digestion is the key to efficient utilization of grain by ruminants (Orskov, 1986). Grain sorghum starch is generally regarded a s less accessible to enzymatic degradation than starch in other grains (Rooney and Pflugfelder, 1986); therefore, improving ruminal digestion of grain sorghum should improve efficiency of utilization by ruminants.
'Published as paper no. 9429, Journal Series, Nebraska Agric. Res. Div. 2Present address: Dept. of h i m . Sci. and Ind., Kansas State Univ., Manhattan 66506. 3To whom correspondence should be addressed. Received December 6, 1990. Accepted April 28, 1992.
Many investigators have reported differences in cattle performance and digestibility among grain sorghum hybrids (Sherrod et al., 1969; McCollough et al., 1972a,b; Hibberd et al., 1979b, 1983; Streeter et al., 1990b, 1991). Our objectives were to assess what variability exists among grain sorghum hybrids for in vitro rate of starch digestion (IVSD) and whether we could manipulate animal performance based on a n estimate of IVSD.
Experimental Procedure
Laboratory EvaZuation. The first phase measured starch content and IVSD of 48 axm'mrcial grain sorghum hybrids. The hybrids examined were entered into the University of Nebraska @;rain sorghum hybrid tests during 1985 and 1986. Grain samples were harvested by hand from nonirrigated test plots and cleaned by hand to remove
2866
Downloaded from https://academic.oup.com/jas/article-abstract/70/9/2866/4705197 by Iowa State University user on 10 January 2019
ABSTRACT: Fortyeight commercial grain sorghum hybrids were ranked on the basis of in vitro starch disappearance (IVSD) and starch content. Starch content ranged from 64.3 to 70.3% ( P < . O l l and IVSD ranged from 5.2 to 6.3 %/h (P < .01). In the next year, 20 experimental grain sorghum hybrids consisting of 17 hybrids being developed for livestock diets and three for human diets were ranked according to IVSD, starch content, and CP content. In these samples, IVSD varied from 6.0 to 9.1 % / h ( P c .05). Starch content and CP were not related to IVSD. Starch content was not correlated to CP content. Four of the original 48 grain sorghum hybrids, selected on the basis of IVSD (two fast and two slow), that differed in IVSD by 7.0% (6.5 to 7.0 %/hl, were fed for 133 d to steers (mean initial BW of 326 kgl. The ADG of steers fed
SORGHUM HYBRIDS AND PERFORMANCE OF RUMINANTS
cate grain samples. Tubes were thoroughly mixed to ensure that the sample was suspended. Another 5 mL of artificial saliva was used to rinse DM from the sides of the tube. Tubes were gassed with C02, stoppered with a one-hole (-1 mm in diameter) stopper, and placed in a 39°C water bath. Tubes were swirled midway during the incubation. Fermentation was terminated at 9 h by adding 1.5 mL of 3.6 M HC1 to each tube. Starch remaining in digested samples was measured as described previously except for the following modifications. All reactions were carried out in centrifuge tubes. After incubation at 3 9 O C, pH of the samples was adjusted to 5.0 with NaOH and 12.5 mL of 1.0 M sodium acetate buffer (pH 5.0) was added to each tube. Tubes were centrifuged for 2 20 min a t 1,500 x g before filtering. The IVSD was calculated by dividing the amount of starch remaining after incubation by the length of incubation. Preliminary experiments indicated that 9 h was in the linear portion of IVSD of sorghums (Figure 1). The values are an average of replications conducted on four different days. A second set of hybrids (entirely different from the 48 hybrids mentioned above) consisted of 17 experimental (not released commercially) hybrids grown for livestock feed and three hybrids grown for human consumption. These hybrids were assayed for IVSD as before except that samples were incubated for 4, 8, 12, 16, and 24 h, and fermentation was terminated by addition of 15 mL of cold (4OC) 1.0 M sodium acetate buffer (pH 5.0) with .2% (wt/voll benzoic acid. The pH of samples did not need to be adjusted with NaOH and no additional buffer was added. The IVSD was calculated by regressing the natural log of percentage of starch remaining in the sample against incubation length. The slope of the regression line represents fractional rate of starch disappearing per hour. Rate values were a n average of replications conducted on three different days. The 17 hybrids (including a bird-resistant hybrid) for livestock consumption were grown under nonirrigated conditions in the same location in eastern Nebraska. The other three hybrids were raised in a nursery with limited irrigation. Crude protein was calculated as total N (Kjeldahl method, AOAC, 1984) multiplied by 6.25. Correlation coefficients of grain composition were calculated using Pearson’s correlation coefficients (SAS, 1985). In this second in vitro experiment, ruminal fluid inoculum was prepared by obtaining aliquots of whole ruminal contents from two steers maintained on a n 80% concentrate diet. The concentrate portion was composed of dryrolled corn and supplement. Ruminal contents were strained through eight layers of cheesecloth and liquid
Downloaded from https://academic.oup.com/jas/article-abstract/70/9/2866/4705197 by Iowa State University user on 10 January 2019
fines, cracked berries, and foreign material. The grain was ground to pass a 1-mm screen in a cyclone-type grinder. Samples were stored at room temperature. Analysis of IVSD was conducted after both years’ samples were obtained. Starch in grain samples was determined as alinked glucose polymers by a modified MacRae and Armstrong (1968) procedure. A .5-g sample of cleaned, ground grain was weighed into a 125-mL Erlenmeyer flask. The sample was suspended in 50 mL of .5 M sodium acetate buffer (pH 5.0) and 100 pL of heat-stable a-amylase (Termamyl 120L, #TC-1000-2436, Fisher Scientific, Pittsburgh, PA) was added. Samples were autoclaved at 121OC for 30 min and a n additional 100 pL of heat-stable a-amylase was added. Flasks were then placed into a boiling water bath for 1 h. Samples were allowed to cool to 5 60°C. Any DM apparent on the sides of the flask was scraped back into the buffer-enzyme solution with a rubber policeman. When flasks had cooled sufficiently, 3 mL of a n amyloglucosidase (#A 7255, Sigma Chemical, St. Louis, M01 solution (250 units/mLl was added and the samples were incubated for 24 h a t 60°C. The suspensions were filtered through fast qualitative filter paper (#410, Schleicher & Schuell, Keene, NH) into 100-mL volumetric flasks. Samples were brought to volume with . 2 O/O (wt/vol) added benzoic acid to inhibit microbial growth in the samples. An aliquot was stored at 4 O C until analysis for glucose was conducted using a n automated procedure (Technicon Instruments Corp., Tarrytown, NY). Starch content was calculated by multiplying the glucose concentration by .9. Rate of starch disappearance was measured by incubating a .5-g sample of grain, cleaned and ground as before, in ruminal fluid. The sample was weighed into a 50-mL polypropylene centrifuge tube. Ruminal fluid inoculum was prepared by obtaining aliquots of whole ruminal contents from two steers One steer was maintained on a 90% concentrate diet. The concentrate portion was composed of dryrolled corn and supplement. The other donor steer was fed alfalfa hay. Ruminal contents were strained through eight layers of cheesecloth and the liquid from each animal was mixed in equal proportions into a warmed Thermos flask. The ruminal fluid was allowed to settle for approximately 10 min before being mixed (1 part grain inoculum: 1 part alfalfa inoculum; 2 parts warm [3Q0C1 artificial saliva [McDougall, 19481 to which 1 g/L urea had been added) and gassed with C02. The mixture was poured into separatory funnels, gassed with COz, and placed in a 39OC water bath for 2 20 min to remove settled and floating material from the inoculum. Fifteen milliliters of inoculum was added to dupli-
2867
2868
WESTER ET AL.
1977). 2.0
''
0
I
I
I
I
I
5
10
15
20
25
'0 30
Incubation time, h
Figure 1. Relationship of average starch remaining across 20 hybrids (after natural logarithmic transformation; * ) and extent of starch disappearance ( 0 )to length of incubation.
from each animal was mixed in equal proportions into a warmed thermos. Ruminal fluid was allowed to settle for approximately 10 min before being mixed in a 2:1 ratio with warm (39°C) artificial saliva (McDougall, 1948) to which 1 g/L of urea had been added and gassed with C02. For comparison of hybrids on the basis of IVSD, analysis of variance was performed using the GLM procedure of SAS (1985) using hybrid, year (in the case of the 48 hybrids), and incubation as independent variables. The hybrid x replication interaction provided the error term. Duncan's multiple range test (protected by a significant F test of P < .10 for hybrid) was used to compare means. To examine the effect of increasing amylopectin content on IVSD, three genetically similar hybrids differing in genes for amylopectin content were tested. A waxy hybrid CATx630 x RTx33381, a heterowaxy hybrid (ATx630 x RTx4351, and a nonwaxy hybrid CATx631 x RTx435) were grown in 1987 at Halfway, TX and characterized as having a white pericarp and heteroyellow endosperm (except for the waxy hybrid, which had a waxy endosperm; grain samples were generously provided by L. w. Rooney, Texas A&M University). The endosperm of the heterowaxy hybrid was phenotypically approximately 25% waxy. The waxy hybrid was openly pollinated so it was only about 95% waxy (L. W. Rooney, personal communication). The IVSD, using five incubation times (4, 8, 12, 16, and 24 h), was determined and statistical analysis performed as previously described except that values represented replications on two different days.
Steer Trial. Ten hybrids (five of the fastest and five of the slowest) of the original 48 were chosen for further in vitro evaluation using five incubation times to determine the starch degradation rate constants (data not shown). Based on rankings of the starch degradation rate constants, and availability of seed (some of the hybrids we wanted to grow for animal experiments were no longer commercially available), two hybrids from the fast group and two from the slow group were selected for planting to generate grain for animal trials. A feedlot trial was conducted to evaluate the effect of IVSD on the finishing performance of
Table 1. Composition of final diets in steer finishing Trial la Grain sorghumb Ingredient
A
B
80.00 5.00 5.00 5.00 2.04 1.35
5.00 5.00 1.90
.46
.46
.31 .30 .16 .10 .10
.45 .30 .16
.09
.09 .OS
C
D
80.00
80.00
80.00
5.00
5.00 5.00
YO
Sorghum Corn silage Alfalfa hay Molasses Feather meal Limestone Urea Finely ground corn Salt Potassium chloride Ammonium sulfate Fat Dicalcium phosphate Trace mineral premixC Vitamin premixd Monensin premixe Tylosin premixf
.05 .01 .02
.01
1.35
.10 .10
.o 1 .02
.o 1
5.00
-
5.00 5.00 5.00
1.59
.10 .10
1.35 .46 .74 .30 .17 .10 .10
.14
.10
.05 .01
.05 .01
.02 .01
.01
1.34 .46 2.30
.30 .17
.02
*Dry matter basis. bGrain sorghum hybrids: A was the hybrid with the fastest in vitro rate of starch digestion (IVSDI (6.95%/h), hybrid D had the slowest IVSD (6.48%/hI, and B and C were intermediate (6.75 and 6.640/o/h, respectively]. CTracemineral premix contained 13.0 to 15.0% Ca, 12.0% Zn, 8.0% Mn, 10.0% Fe, 1.5% Cu, .2% I, and .lob Co. dVitamin premix contained 30,000 IU/g of vitamin A, 6,000 IU/g of vitamin D, and 7.5 IU/g of vitamin E. eMonensin premix 132 g/kg. fTylosin premix 88 g/kg.
Downloaded from https://academic.oup.com/jas/article-abstract/70/9/2866/4705197 by Iowa State University user on 10 January 2019
The effect of removing tannins from a hightannin Bird-resistant) hybrid was studied by measuring IVSD of pearled grain, Samples of grain were pearled until approximately 25%, by weight, of the grain had been removed (Chibber et al., 1978). Pearled and unprocessed grains were evaluated by incubating samples for five incubation times (4, 8, 12, 16, and 24 h). Tannins were measured as catechin equivalents by the vanillinhydrochloric acid method (Guiragossian et al.,
SORGHUM HYBRIDS AND PERFORMANCE OF RUMINANTS
Table 2. Composition of diets in lamb finishing Trial 2a Grain sorghumb Ingredient
A1
A
D
BR
72.00
72.00
20.00
2.00 3.00
YO
Sorghum Finely ground alfalfa hay Molasses supplementC Limestone Molasses Feather meal Finely ground corn
72.00 20.00 3.00 .50 4.00
.40 .10
72.00 20.00 3.00 .SO 3.36 1.14
-
3.00 .50 4.00
.SO
.50
3.21 1.29
-
*DM basis. bGrain sorghum hybrids: A1 was the hybrid with the fastest in vitro rate of starch digestion (IVSD) (6.83%/h), hybrid D had the slowest IVSD (6.24%/h),and A and BR were intermediate (6.60 and 6.31%/h, respectively). Hybrids A and D were also used in the steer trial and BR was a high-tannin hybrid. CSupplement was based on molasses and urea liquor and contained on a dry matter basis 50.6% crude protein, 2.61% K, 2.25% Fe, 1.0% Zn, .95% Ca, .64% Mn, .55% I, .55% P, . 4 1 % S, 3 5 % Mg, .20% Cu,.16% Co, 16,287IU of vitamin A/kg, 3258 IU of vitamin D/kg, and 4 IU of vitamin E/kg.
NE. Lambs had free access to water. Three lambs were removed from the study because of illness and were not included in cumulative measurements. Lambs were adjusted to a d libitum intake with incremental increases (.28% of BW) made every 2 d in the amount of feed offered. Most lambs had achieved ad libitum intake within 20 d. Diets were fed once daily for a total of 85 d. Feed samples and orts were collected weekly for DM analysis. In addition to grain sorghum, the diets contained 20% finely ground (to pass a 12.5-mm screen) alfalfa hay, 3% molasses-urea liquor-based supplement (50.6% CP), and .5% limestone. The remaining 4 . 5 % of the diet DM was derived from feather meal, molasses, and finely ground corn (to pass a 6.4 mm-screen). Diets were formulated (DM basis) to contain 12.8% CP, .6% Ca, . 4 % P, and .8% K. Initial and final BW were the average of weights taken on three consecutive days during which, and including 1 d prior, lambs were fed a constant percentage of BW to minimize differences in gut fill. Analysis of variance of lamb performance was conducted as outlined by Steel and Torrie (1980) for a randomized complete block design with block and treatment as main effects and residual as the error term. Least squares means and lsd were computed using the GLM procedure of SAS (1985). The IVSD of grain hybrids fed to lambs, grown in 1988, was determined and analyzed as described previously for the steer trial. Performance of the steers and lambs was correlated to IVSD by calculating simple correlation coefficients between treatment means and IVSD.
Downloaded from https://academic.oup.com/jas/article-abstract/70/9/2866/4705197 by Iowa State University user on 10 January 2019
steers. Selected hybrids were grown in 1988 at the University of Nebraska Agricultural Research and Development Center a t Mead, NE and were fed dry-rolled at 80% of the final dietary DM (Table 1) to 128 mixed crossbred steers (mean initial BW of 326 k 9 kg) allotted randomly to four treatments. Each treatment was replicated in four pens. Steers were housed in 3.7-m x 6.1-m pens within a threesided barn with southerly exposure and were allowed free access to water. Steers were allowed a d libitum access to feed for a total of 133 d starting on December 15, 1988, and ending on April 28, 1989. Steers were adapted to the final diets by adjusting roughage levels from 71, 57, 45, and 25% (corn silage-alfalfa mixture) for 3, 3, 7, and 7 d, respectively. All diets were fed once daily and formulated (DM basis) to contain .70% Ca, .35% P, .70% K, 27.5 mg/kg of monensin (Elanco Products, Indianapolis, IN), and 11.0 m g k g of tylosin (Elanco Products). Final diets were formulated (DM basis) to contain 13.1% CP, because this was the amount of protein present in the nonprotein supplemented diet that consisted of the hybrid with the highest CP (Diet C). Feather meal was used in the other diets to balance to 13.1% CP. The remaining 20% of the dietary DM was derived equally from corn silage, alfalfa hay, molasses, and supplement. Steers were implanted with estradiol-17p (Elanco Products). Initial weight was the average of weights taken on two consecutive days, and final weight was estimated by adjusting the hot carcass weight to a 62% dressing percentage. Hot carcass weight and liver score (incidence and severity of liver abscesses) were recorded a t time of slaughter, and 12th rib fat thickness and quality grade were measured after a 48-h chill. The IVSD of the grain hybrids fed to the steers, produced in 1988, was determined and analyzed as described previously using five incubation times. Analysis of variance of steer performance and carcass characteristics was performed as outlined by Steel and Torrie (1980) for a completely random design. Least squares means and lsd were computed using the GLM procedure of SAS (1985). Lamb Trial. Four grain sorghum hybrids, including Hybrids A and D from Trial 1, a bird-resistant hybrid, and a hybrid with an IVSD similar to that of Hybrid A were grown at the University of Nebraska Agricultural Research and Development Center a t Mead, NE in 1988. Hybrids were dry-rolled and fed as 72% of the dietary DM (Table 2) to mixed crossbred finishing lambs (mean initial BW of 28 f 2 kg) in a randomized complete block design. Forty lambs (24 wethers and 16 ewes) were assigned to 10 blocks according to weight and sex and were assigned randomly to individual pens (.84 m21 in the Animal Science Complex, Lincoln,
2869
WESTER ET AL.
2870
Results and Discussion
1980).
Downloaded from https://academic.oup.com/jas/article-abstract/70/9/2866/4705197 by Iowa State University user on 10 January 2019
Grain sorghum hybrids evaluated in these studies were chosen from University of Nebraska hybrid testing for the 48 varieties. Hybrids selected for the steer trial were selected from this initial screening. The second group of hybrids tested for IVSD were experimental hybrids that were not released for commercial use and were grown in the same year and most of them in the same location. None of the hybrids in the 48-sample test was present in the second group of hybrids. The second group of hybrids and the 48 hybrids used in the initial study and the animal trials were grown in different years. Labovatory Evaluation. The IVSD values of the hybrids ranged from 5.2 to 6.3%/h (Table 3). Hybrids with the nine fastest IVSD values were different from hybrids with the two slowest (P e .05). Hybrid IVSD was affected by year and replication (P c .01; data not shown), but no interaction between hybrid and year was observed. Significant replication variation suggests that IVSD values should not be taken as absolute, but rather as relative, values within a series of incubations. Therefore, IVSD values presented in our paper should be viewed in that context. The IVSD values reported within each table in our paper were run simultaneously and can be compared; however, IVSD values reported in different tables were during different incubations home in different years), and absolute values should not be compared. Lack of a n interaction between hybrid and year suggests that selection or ranking of hybrids could be made based on IVSD. Among the 48 hybrids tested, total starch content ranged from 64.3 to 70.3% of DM (P c .01, Table 3). Hibberd et al. (1979b) demonstrated that starch content varied among eight selected grain sorghum genotypes from 66.6 to 79.5%. Starch content of the hybrids also differed (P e .01) between growing years, indicating that environmental factors affect starch content. Bach Knudsen et al. (1987a,b) found that DE and starch content of different varieties of barley were affected by year and location grown, although there was no interaction between variety and year. These authors also determined that differences existed within a varietal type in response to year and location. Goldy et al. (1986) examined 15 hard red winter wheat varieties and concluded that for many quality variables, differences were greater for location than for variety. Hibberd et al. (1980) indicated that for grain sorghum hybrids in their study, CP was affected by a hybrid x location interaction, whereas starch content was not. Also, IVDMD was affected by location (Hibberd et al.,
In our second set of hybrids compared, the two hybrids with the fastest IVSD values were different (P c .lo) from the six hybrids with the slowest rates (Table 4). Hybrids used for human consumption ranked first (9.l%/hl, sixth (7.7%/h), and eighteenth (6.7%/h) in the overall comparison. Food hybrids all had a cream-colored pericarp, a trait that is used to improve the aesthetic quality of flour. The average disappearance curve for starch across hybrids was linear when amount of starch remaining, after natural logarithmic transformation, was plotted against incubation time (R2= ,961, Figure 1). Galyean et al. (19811 observed that starch disappearance in corn, in situ, consisted of a rapidly ( e 2 h) degraded fraction, after which starch disappeared at a slower rate. A rapidly degraded starch fraction was not apparent in our data. Total starch and CP content of the grain were not related to IVSD Ir = .094, P = .69 and r = .047, P = .84, for starch and CP, respectively). Taylor et al. (1984) reported that increased protein content of sorghum grain increased the prolamin fraction (endosperm storage proteins). This report suggests that a hybrid with high CP may have a lower IVSD if the relationship between prolamins and starch digestion is negative. No clear evidence exists linking prolamin content and starch digestibility of grain; however, Sullins and Rooney (1974) speculated that prolamins reduced starch availability in sorghums. Chandrashekar and Kirleis (1988) pointed out that increased sorghum grain protein is related to increased numbers of prola min-rich protein storage bodies. The increased amount of protein bodies present may result in denser and thicker peripheral and vitreous endosperms, which could make starch present in those layers and within the floury endosperm less available to enzymatic degradation. Our results do not support this hypothesis. Similarly, the lack of correlation between CP and percentage of vitreousness reported by Cagampang and Kirleis (1984) also does not support this hypothesis. Among hybrids studied by Cagampang and Kirleis (19841, starch and CP content were not correlated. Chandrashekar and Kirleis (19881 also reported no correlation of starch and protein. Some of the similarity observed in IVSD among hybrids is likely the result of close genetic relationship. Parental cultivar crosses of commercial hybrids are not publically known and there may be, in fact, only a small number of parental cultivars actually used in commercial hybrid production IB. E. Johnson, USDA grain geneticist, Lincoln, NE, personal communication). Therefore, hybrids with similar IVSD may be closely related genetically.
2871
SORGHUM HYBRIDS AND PERFORMANCE OF RUMINANTS
We evaluated the next group of hybrids, which varied in the waxy gene, because they were closely related genetically and were grown a t the same location in the same year. Although we did not measure amount of amylopectin in these samples, different genotypes are known to produce differ-
ences in grain amylopectin content. Therefore, this was a n opportunity to examine effects of the different waxy gene hybrids on IVSD. The waxy hybrid had the fastest IVSD value, whereas the nonwaxy had the slowest IVSD, and the heterowaxy IVSD was intermediate (Table 51. Differ-
Table 3. Rank of 48 test hybrids by nine-hour in vitro starch digestion
1 2 3 4 5 8 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 38 37 38 39 40 41 42 43 44 45 48 47 48
SE
N
Total starch, % & 68.4 64.3 66.6 87.7 67.3 86.9 88.5 67.1 89.1 68.5 68.4 66.3 65.3 66.9 68.9 67.7 66.4 66.3 65.8 67.8 87.8 68.0 69.8 70.3 65.2 66.7 66.6 66.0
65.5 66.9 69.0 64.3 66.8 68.0 68.3 67.3 68.5 66.1 67.6 67.9 66.8 66.1 68.8 87.8 86.7 67.3 65.0 69.5 .57 4
IVSD~ 6.3 6.1 6.1 8.1 6.0 5.9 5.9 5.9 5.9 5.8 5.8 5.8 5.8 5.8 5.8 5.7 5.7 5.7 5.7 5.7 5.8 5.8 5.8 5.8 5.8 5.8 5.8 5.8 5.8 5.8 5.8 5.5 5.5 5.5 5.5 5.5 5.5 5.5 5.5 5.5 5.4 5.4 5.4 5.4 5.4 5.4 5.3 5.2 .l8 4
Extent of starch disappearance, % 56.3 55.2 54.7 54.4 53.8 53.1 53.1 53.0 52.9 52.2 52.2 52.2 51.9 51.8 51.8 51.7 51.8 51.4 51.2 51.0 50.6 50.6 50.8 50.6 50.5 50.3 50.3 50.2 50.1 50.0 50.0 49.9 49.7 49.6 49.5 49.4 49.3 49.1 49.1 49.0 48.9 49.8 48.7 48.6 48.3 48.3 47.7 47.2 1.44 4
IVSD Duncan’s groupingC A A A A A A A A A A A A A A A A A
B B C B C D B C D E B C D E F B C D E F B C D E F B C D E F B C D E F G B C D E F G B C D E F G B C D E F G B C D E F G B C D E F G B C D E F G B C D E F G B C D E F G B C D E F G B C D E F G B C D E F G B C D E F G B C D E F G B C D E F G B C D E F G B C D E F G B C D E F G B C D E F G C D E F G C D E F G C D E F G C D E F G C D E F G D E F G D E F G D E F G E F G E F G E F G E F G E F G E F G E F G E F G F G F G G G
-
&Dry matter starch content of whole, cleaned grain. bIVSD = in vitro rate of starch disappearance expressed in percentage of starch portion disappearing per hour. The values are an average of replications conducted on four different days. CDuncan’smultiple range test performed on IVSD. Hybrids without common letters differ ( P < .05).
Downloaded from https://academic.oup.com/jas/article-abstract/70/9/2866/4705197 by Iowa State University user on 10 January 2019
Grain sorghum hybrid
WESTER ET AL.
2872
Table 4. Characteristicsa of grain sorghum hybrids used for in vitro Trial 2
Hybrid
Pericarp color
Starch, 016
IVSDb
~
ld 2
3 5 gd
7 8 9
10 11 12 13 14 15 16 17 18d 19 20e SE n
9.1 9.1 8.7 8.5 7.7 7.7 7.6 7.5 7.5 7.3 7.2 7.2 7.1 7.0
66.6
66.5 67.9 67.9 68.8 71.0 70.2 71.0 70.9 67.3 71.6 69.5 69.5
6.9
6.9 6.8 6.7 6.6 6 .O
66.6
1.25 2
-
YO
~
68.5 70.4 71.0 69.3 68.7 68.5
-
CP,
IVSD Duncan's groupingC
.60
3
87.1 86.1 85.5 85.1 83.4 83.1 81.1 83.6 82.7 81.1 82.8 82.8 81.8 81.1 80.6 81.1 80.6
79.0 77.9 75.8 1.99 3
10.4
11.0 11.8 9.5 11.5
10.3 12.1 11.6 10.9 11.3 11.5 12.0 11.5 11.3 10.8 10.6 10.7 9.3 10.8 11.5 .07 2
A A A A A A A A A
B BC B C D B C D BCD BCD BCD B C D B C D B C D B C D B C D C D C D C D D D D
-
-
*Dry matter basis. bIVSD = in vitro rate of starch disappearance expressed as the fractional rate of starch disappearing per hour. The values are an average of replications conducted on three different days. CDuncan's multiple range test performed on IVSD. Hybrids without common letters differ (P < ,101. dGrain sorghum grown for human consumption. eBird-resistant, high-tannin sorghum.
ences observed in IVSD among hybrids should have resulted only from differences in genotype of the hybrid. Differences observed among IVSD values of the waxy, heterowaxy, and nonwaxy hybrids were predictable considering the changing composition of starch in the grains. Amylopectin, the primary component [ > 95%) of waxy starches, is more susceptible to enzymatic degradation than are normal starches (Rooney and Pfugfelder, 19861.
Hibberd et al. (1979b)observed that waxy sorghum grain had the greatest IVDMD and in vitro gas production. Streeter et al. (1990a) reported similar results. The IVSD data presented here represent the only comparison of genetically similar hybrids differing primarily in waxiness of the starch. It is plausible that the increase in amylopectin concentration was partially responsible for the increase in IVSD observed; however, other factors (not
Table 5. Characteristicsa of grain sorghum hybrids differing in degree of waxiness
Hybrid ATx630 x RTx3338 ATx630 x RTx435 ATx631 x RTx435 SE n
Endosperm type
CP,
Starch,
%
%
IVSDbC
Waxy Heterowaxy Nonwaxy
1.3 12.1 11.2 .07
73.7 71.6 72.3 .75
8.2 7.7 7.2 .13 2
-
2
2
Extent of starch disappearance at 24 h, % 85.1 82.0 79.4
1.61 2
*Dry matter basis. n = 2. bIVSD = in vitro rate of starch disappearance expressed as the fractional rate of starch disappearing per hour. The values are an average of replications conducted on two different days. CContrasts:waxy vs heterowaxy, P = .11; waxy vs nonwaxy, P = .03; heterowaxy vs nonwaxy, P = .12.
Downloaded from https://academic.oup.com/jas/article-abstract/70/9/2866/4705197 by Iowa State University user on 10 January 2019
4
Cream Bronze Bronze Cream Bronze Cream Bronze Bronze Bronze Bronze Bronze Bronze Cream Bronze Red Bronze Cream Cream Cream Bronze
Extent of starch disappearance at 24 h, Oh
SORGHUM
HYBRIDS AND PERFORMANCE OF RUMINANTS
2873
Table 6. Effect of pearling on the characteristicsa of high-tannin grain sorghum
CP,
Starch,
To b
%
010
Unprocessed Pearled SE n
4.84 .62
9.6 8.4 .04 2
2
69.5 80.5 .76 3
.
IVSDC 5.3 5.8 .31 5
72.9 76.8 1.52 5
&Dry matter basis. bExpressed on a DM basis as catechin equivalents. CIVSD = in vitro rate of starch disappearance expressed as the fractional rate of starch disappearing per hour. The values are a n average of replications conducted on five different days.
measured) that could change with different genotypes of the hybrids may also have been responsible for changes in IVSD. Because one of the hybrids used in the sheep trial was bird-resistant, we wanted to know whether the tannins in the grain affected IVSD. Removing 25% of the weight of the grain by pearling resulted in removal of just over 87% of the tannin (as measured by catechin equivalents; Table 6). The IVSD of pearled grain did not differ from that of unprocessed grain (P = .331, suggesting that the materials removed by pearling were not responsible for the reduced IVSD observed with bird-resistant hybrids. Level of catechin equivalents in the pearled grain was 120 to 700% greater than that found in low-tannin hybrids (Chibber et al., 1978; Taylor et al., 19841. Chibber et al. (1978)were able to remove 74.6% of the tannins when 24.6% of the weight of a high-tannin hybrid was removed by pearling. When 37% of the weight was removed, only 2.4% of the tannin remained; the most tannin removed by pearling was 98%. Bird-resistant hybrids have been reported to be less digestible than hybrids
with low tannin content (Hibberd et al., 1979a, 1982a; Streeter et al., 1986). Possibly, tannin remaining in the grain after pearling was sufficient to cause reduced enzymatic activity and suppress starch digestion. Streeter et al. (1990~1reported a tendency (P = ,131 for ruminal starch digestibility to be greater for bird-resistant hybrids than for a waxy counterpart or a millrun sorghum. Tannin is only one of the polyphenols associated with birdresistant sorghums and is not directly measured by the vanillin-HC1 method commonly used to determine tannin content (Daiber, 1975). Therefore, whether tannins (polyphenols) were not sufficiently removed to reduce their negative effect on enzyme activity or whether there are other factors inherent in the grain that limited enzyme activity (or otherwise caused decreased IVSD) could not be distinguished in our study. Animal TriaZs. Differences in steer performance were observed primarily when we compared the steers fed Hybrid A, which had the fastest IVSD, to those fed Hybrid D, which had the slowest IVSD (Table 7). Steers fed A had 9.0% faster ADG than steers fed D (P = .06).No treatment differences
Table 7. Effect of sorghum hybrid on steer performance and carcass characteristics Grain sorghum Item Grain IVSD, % / h a DMI, kg/d ADG, kg Gain/feed Liver scoree 12th rib fat, mm Quality gradef
A ?.Ob 9.92 1.33b .135 .09 12.57 18.66
B 6.8' 9.48 1.24bC ,131 .12 11.43 18.76
C 6Bcd 10.07 1.30bC ,129 .03 12.19 18.62
D 6.5d 9.57 1.22c .128 .09 11.37 18.25
SE .07 .23 .04 .004 .06 .OB
.19
'IVSD = in vitro rate of starch disappearance expressed as the fractional rate of starch disappearing per hour. The values are a n average of replications conducted on three different days. b,c,dWithin rows, values without common superscripts differ (P c .lo). eLiver score: 0 = healthy liver, 1 = one or two small abscesses, 2 = two to four active abscesses, 3 = one or more large abscesses, 4 = adherence of abscess to diaphragm or gut. fQuality grade: Choice = 19, Select+ = 18, Select" = 17.
Downloaded from https://academic.oup.com/jas/article-abstract/70/9/2866/4705197 by Iowa State University user on 10 January 2019
Tannin, Sample
Extent of starch disappearance at 24 h, %
2874
WESTER ET AL.
,136
,134
I
1.215
I
A
.210
R2= .94
.195
5
Q (D
(D
.I90
6.2
,180
6.4
6.6
6.8
7.0
In vitro starch disappearance,%/h
Figure 2. Relationship of in vitro starch disappearance to gain:feed in cattle (- W -1 and lamb (- - A - -] trials.
were observed in gain:feed, DMI, liver score, 12th rib fat thickness, or quality grade among treatments; however, simple correlations of the means of gain:feed IVSD revealed a strong (R2 = .94) relationship (Figure 2). A similar relationship between IVSD and gain:feed when different grain sorghum processing methods were evaluated was reported by Stock et al. (1987). In the sheep trial, none of the IVSD values for hybrids differed, but the relationship between Hybrid A and Hybrid D was similar to the data obtained on the same hybrids for the steer trial (Table 8). Overall, there were no differences CP > .lo) for DMI and ADG for lambs among the four hybrids. Lambs fed A were more efficient (gain: .05). The feed) than lambs fed A1 and BR (P hybrid (All with the fastest (numerically) IVSD also resulted in the lowest gain:feed. The possibility that subacute acidosis caused reduced performance of lambs fed A1 does not seem likely because intake was not reduced, a common sign of acidosis (Britton and Stock, 1986).
Table 8. Effect of sorghum hybrid on lamb performance Grain sorghum Item Grain IVSD,%/ha DMI, g/d ADG, g
Gain/feed
6.6 1,305 289 .2lOb
0.2 1,365 281 .200bC
6.8 1,363 273
.VMc
6.3 1,377 274 .188C
.26 38.1 12.5 ,008
&IVSD = in vitro rate of starch disappearance expressed as the fractional rate starch disappearing per hour. The values are an average of replications conducted on three different days. .101. b*cWithinrows, values without common superscripts differ (P
Downloaded from https://academic.oup.com/jas/article-abstract/70/9/2866/4705197 by Iowa State University user on 10 January 2019
// 1: 9 I - - _._
,126
Although steer efficiencies were related to IVSD, efficiencies from the lamb trial exhibited no relationship (Figure 2). We expected that gainfeed would be positively correlated with ruminal digestibility of sorghum and, therefore, to IVSD. Mertens and Ely (1982) reported that feed digestibility by lambs was less than that by cattle when digestibilities were c 66% and greater by sheep than by cattle when digestibilities were > 66%. One explanation for the lack of difference observed in our lamb trial may be that lambs are less sensitive to changes in IVSD because of their greater inherent digestibility of highly digestible feeds. Lambs fed the high-tannin BR did not perform as well as those fed A and D. Bird-resistant sorghums have lower digestibilities and result in decreased animal performance compared with low-tannin hybrids (Rooney and Pflugfelder, 1986). We have no explanation for the relationship between the performance of lambs fed BR and those fed A1. Broilers fed Hybrid A1 had 12.1% greater ME intake and greater weight gain and efficiency than broilers fed the BR hybrid (Douglas et al., 1990a). This resulted in the same rate of gain and efficiency of birds fed A1 as those fed a corn-based control diet (Douglas et al., 1990b). Previous studies have dealt mainly with in vitro assessment (Hibberd et al., 1979b, 1982b; Streeter et al., 1990a) or in vivo digestibility (Hibberd et al., 1983; Streeter et al., 1990b, 1991) of divergent lines of grain sorghum. McCollough et al. (1972a1 compared the feedlot performance of cattle fed eight grain sorghum hybrids and found that differences existed among hybrids with similar kernel characteristics. They found a > 10% difference in feed efficiency among hybrids with the same endosperm type (yellowl. Carcass characteristics did not differ among steers fed different hybrids. No correlation was evident between feed efficiency and in vitro gas production (McCollough, 1972). Hybrids in the studies of McCollough (1972) were grown under similar conditions; thus, differences observed in performance of steers fed those hybrids could have been directly attributed to genetic variation that existed among those
SORGHUM HYBRIDS AND PERFORMANCE OF RUMINANTS
Implications Our research illustrates that variability in in vitro starch digestion exists among commercially available grain sorghum hybrids, and this variability may affect cattle performance. In vitro starch disappearance, as an index of ruminally available starch, may be a useful selection criterion in a breeding program designed to increase the value of minimally processed sorghum grain. The lamb trial showed, however, that increased rate of ruminal starch digestion is not an absolute predictor of animal performance and that other factors can affect performance of finishing ruminants.
Literature Cited AOAC. 1984. Official Methods of Analysis (14th Ed.).Association of Official Analytical Chemists, Arlington, VA. Bach Knudsen, K.E.B.. P. Aman, and B. 0. Eggum. 1987a. Nutritive value of Danish-grown barley varieties. I. Carbohydrates and other major constituents. J. Cereal Sci. 6:173. Bach Knudsen, K.E.B.,P. Aman, and B. 0. Eggum. 1987b.Nutritive value of Danish-grown barley varieties. 11. Effect of carbohydrate composition on digestibility of energy and protein. J. Cereal Sci. 6:187. Britton, R. A,, and R. A. Stock. 1986. Acidosis, rate of starch digestion and intake. In: F. N. Owens (Ed.) Symposium Proceedings: Feed Intake by Beef Cattle. p 125. Oklahoma Agric. Exp. Sta. MP-121. Cagampang, G. B., and A. W. Kirleis. 1984. Relationship of sorghum grain hardness to selected physical and chemical measurements of grain quality. Cereal Chem. 65:lOO. Chandrashekar, A., and A. W. Kirleis. 1988. Influence of protein on starch gelatinization in sorghum. Cereal Chem. 65:457. Chibber, B.A.K., E. T. Mertz, and J. D. Axtell. 1978. Effects of dehulling on tannin content, protein distribution and quality of high and low tannin sorghum. J. Agric. Food Chem. 26579. Daiber, K. H.1075. Enzyme inhibition by polyphenols of sorghum grain and malt. J. Sci. Food Agric. 26:1399. Douglas, J. M., T. W. Sullivan, P. L. Bond, and F. J. Struwe. 199Oa. Nutrient composition and metabolizable energy values of selected grain sorghum varieties and yellow corn. Poult. Sci. 69:1147. Douglas, J. M., T. W. Sullivan, P. L. Bond, F. J. Struwe, J. G. Baier, and L. G. Robeson. 1990b. Influence of grinding, rolling, and pelleting on the nutritional value of grain SOT. ghums and yellow corn for broilers. Poult. Sci. 69:2150. Galyean, M. L., D. G. Wagner, and F. N. Owens. 1981. Dry
matter and starch disappearance of corn and sorghum as influenced by particle size and processing. J. Dairy Sci. 64: 1804. Goldy, G., J. Riley, G. Posler, A. Lenssen, and T. Walters. 1986. Effect of variety, location and irrigation on selected criteria for evaluating wheat as a feed for ruminants. p 1. Kansas State Univ. Cattlemen’s Day Report. Gramlich, S. M. 1988. Grain hybrids and starch utilization in ruminants. M.S. Thesis. University of Nebraska, Lincoln. Guiragossian, V. Y.,S. W. Van Scoyoc, and J. D. Axtell. 1077. Chemical and Biological Methods for Grain and Forage Sorghum. Dept. of Agronomy, Agric. Exp. Sta., Purdue Univ., West Lafayette, IN. Hibberd, C. A., R. L. Hintz, and D. G. Wagner. 1980. The effect of location on the nutritive characteristics of several grain sorghum hybrids. Anim. Sci. Res. Rep., Oklahoma Agric. Exp. Sta. MP-107:102. Hibberd, C. A., E. D. Mitchell, D. G. Wagner, and R. L. Hintz. 1979a. Seed characteristics of different varieties of grain sorghum. Anim. Sci. Res. Rep., Oklahoma Agric. Exp. Sta. MP-104:16. Hibberd, C. A., D. G. Wagner, and R. L. Hintz. 1982a. Effect of stage of maturity on the chemical composition and in vitro digestibility of sorghum grain. Anim. Sci. Res. Rep., Oklahoma Agric. Exp. Sta. MP-112:178. Hibberd, C. A,, D. G. Wagner, R. L. Hintz, and D. D. Griffen. 1983. Effect of sorghum grain variety and processing method on the site and extent of starch digestion in steers. h i m . Sci. Res. Rep., Oklahoma Agric. Exp. Sta. MP-114:28. Hibberd, C. A,, D. G. Wagner, R. L. Schemm, E. D. Mitchell, Jr., R. L. Hintz, and D. E. Weibel. 1982b. Nutritive characteristics of different varieties of sorghum and corn grains. J. Anim. Sci. 55665. Hibberd, C. A,, D. E. Weibel, R. L. Hintz, and D. G. Wagner. 1979b. The influence of variety on nutritive characteristics of grain sorghum. Anim. Sci. Res. Rep., Oklahoma Agric. Exp. Sta. MP-104:12. MacRae, J. C., and D. G. Armstrong. 1968. Enzyme methods for determination of alpha-linked glucose polymers in biological materials. J. Sci. Food Agric. 19:578. McCollough, R. L. 1972. Nutritive value of eight hybrid sorghum grains and three hybrid corns compared in all-concentrate rations. Part I: Hybrid sorghum and corn characteristics and methods used to evaluate them. Kansas Agric. Exp. Sta. Bull. 557~15. McCollough, R. L., C. L. Drake, and G. M. Roth. 1972a. Nutritive value of eight hybrid sorghum grains and three hybrid corns compared in all-concentrate rations. Part 11. Feedlot performance of eight hybrid sorghum grains and three hybrid corns. Kansas Agric. Exp. Sta. Bull. 557:21. McCollough, R. L., J. G. Riley, C. L. Drake, and G. M. Roth. 1972b. Feedlot performance on nine hybrid sorghum grains fed to steers winter, 1971-1972. Kansas Agric. Exp. Sta. Bull. 557:37. McDougall, E. I. 1948. Studies on ruminant saliva. I. The composition and output of sheep’s saliva. Biochem. J. 43:99. Mertens, D. R., and L. 0. Ely. 1982. Relationship of rate and extent of digestion to forage utilization-A dynamic model evaluation. J. Anim. Sci. 54:895. IZlrskov, E. R. 1986. Starch digestion and utilization in ruminants. J. Anim. Sci. 63:1624. Rooney, L. W., and R. L. Pflugfelder. 1986. Factors affecting starch digestibility with special emphasis on sorghum and corn. J. Anim. Sci. 63:1607. SAS. 1985. SAS User’s Guide: Statistics. SAS Inst. Inc., Cary, NC. Sherrod, L. B., R. C. Albin, and R. D. Furr. 1969. Net energy of regular and waxy sorghum grains for finishing steers. J. Anim. Sci. 29:997. Steel, R.G.D., and J. H. Torrie. 1980. Principles and Procedures
Downloaded from https://academic.oup.com/jas/article-abstract/70/9/2866/4705197 by Iowa State University user on 10 January 2019
hybrids. Gramlich (1988) observed that lamb finishing performance was affected by sorghum hybrid. Lambs fed a grain sorghum hybrid selected on the basis of high forage digestibility after grain harvest had lower ADG and were more efficient than those fed a hybrid selected on the basis of low forage digestibility and two grain sorghum hybrids unselected for forage digestibility. Our in vitro data and animal performance trials indicate that rate of grain sorghum starch digestion may influence the feeding value of grain sorghum.
2875
2876
WESTER ET AL. and in vitro gas production of sorghum grain varieties. h i m . Sci. Res. Rep., Oklahoma Agric. Exp. Sta. MP-108:91. Streeter, M. N., D. G. Wagner, F. N. Owens, and C. A. Hibberd. 1991. The effect of pure and partial yellow endosperm sorghum grain hybrids on site and extent of digestion in beef steers. J. Anim. Sci. 00:2571. Stock, R. A,, D. R. Brink, K. K. Kreikemeier, and K. K. Smith. 1987. Evaluation of early-harvested and reconstituted grain sorghum in finishing steers. J. Anim. Sci. 65:548. Sullins, R. D., and L. W. Rooney. 1074. Microscopic evaluation of the digestibility of sorghum lines that differ in endosperm characteristics. Cereal Chem. 51:134. Taylor, J.R.N., L. Schussler, and W. H. van der Walt. 1984. Fractionation of proteins from low-tannin sorghum grain. J. Agric. Food Chem. 32:140.
Downloaded from https://academic.oup.com/jas/article-abstract/70/9/2866/4705197 by Iowa State University user on 10 January 2019
of Statistics: A Biometrical Approach (2nd Ed.). McGrawHill Book Co., New York. Streeter, M. N., D. G. Wagner, C. A. Hibberd, E. D. Mitchell, Jr., and J. W. Oltjen. 199Oa. Effect of variety of sorghum grain on digestion and availability of dry matter and starch in vitro. Anim. Feed Sci. Tech. 29:279. Streeter, M. N., D. G. Wagner, C. A. Hibberd, and F. N. Owens. 1990b. Comparison of corn with four sorghum grain hybrids: Site and extent of digestion in steers. J. Anim. Sci. 68:3420. Streeter, M. N., D. G. Wagner, C. A. Hibberd, and F. W. Owens. 1 9 9 0 ~ .The effect of sorghum grain variety on site and extent of digestion in beef heifers. J. Anim. Sci. 68:1121. Streeter, M. N., D. G. Wagner, C. A. Hibberd, F. N. Owens, and D. S. Buchanan. 1086. In vitro dry matter disappearance
Hybrid A (fastest IVSD) was 9.0% faster than that of steers fed Hybrid D (slowest IVSD; 1.33 vs 1.22 kg, P = .06). Gain:feed ratio was positively correlated with IVSD across all treatments (R2= .94). Hybrids A and D, another Hybrid, Al, and a birdresistant hybrid (BR) were fed for 85 d to finishing lambs h e a n initial BW of 28 kg). Lambs fed Hybrid A gained more efficiently (gain:feed) than those fed BR or A1 (.210 vs .188 and .184, P c .05), and those fed D were intermediate (2001. Performance of sheep fed A l , with the fastest IVSD, and those fed BR, with the lowest IVSD, were similar, suggesting that factors other than IVSD affected lamb performance. Our data indicate that rate of grain sorghum starch digestion may influence feeding value of grain sorghum fed to cattle.
Key Words: Sorghum, Starch, In Vitro Digestibility, Sheep, Beef Cattle
J. Anim. Sci. 1992. 70:2866-2876
Introduction As the major component of cereal grains, starch is the primary dietary energy source for the beef feedlot industry. Ruminal starch digestion is the key to efficient utilization of grain by ruminants (Orskov, 1986). Grain sorghum starch is generally regarded a s less accessible to enzymatic degradation than starch in other grains (Rooney and Pflugfelder, 1986); therefore, improving ruminal digestion of grain sorghum should improve efficiency of utilization by ruminants.
'Published as paper no. 9429, Journal Series, Nebraska Agric. Res. Div. 2Present address: Dept. of h i m . Sci. and Ind., Kansas State Univ., Manhattan 66506. 3To whom correspondence should be addressed. Received December 6, 1990. Accepted April 28, 1992.
Many investigators have reported differences in cattle performance and digestibility among grain sorghum hybrids (Sherrod et al., 1969; McCollough et al., 1972a,b; Hibberd et al., 1979b, 1983; Streeter et al., 1990b, 1991). Our objectives were to assess what variability exists among grain sorghum hybrids for in vitro rate of starch digestion (IVSD) and whether we could manipulate animal performance based on a n estimate of IVSD.
Experimental Procedure
Laboratory EvaZuation. The first phase measured starch content and IVSD of 48 axm'mrcial grain sorghum hybrids. The hybrids examined were entered into the University of Nebraska @;rain sorghum hybrid tests during 1985 and 1986. Grain samples were harvested by hand from nonirrigated test plots and cleaned by hand to remove
2866
Downloaded from https://academic.oup.com/jas/article-abstract/70/9/2866/4705197 by Iowa State University user on 10 January 2019
ABSTRACT: Fortyeight commercial grain sorghum hybrids were ranked on the basis of in vitro starch disappearance (IVSD) and starch content. Starch content ranged from 64.3 to 70.3% ( P < . O l l and IVSD ranged from 5.2 to 6.3 %/h (P < .01). In the next year, 20 experimental grain sorghum hybrids consisting of 17 hybrids being developed for livestock diets and three for human diets were ranked according to IVSD, starch content, and CP content. In these samples, IVSD varied from 6.0 to 9.1 % / h ( P c .05). Starch content and CP were not related to IVSD. Starch content was not correlated to CP content. Four of the original 48 grain sorghum hybrids, selected on the basis of IVSD (two fast and two slow), that differed in IVSD by 7.0% (6.5 to 7.0 %/hl, were fed for 133 d to steers (mean initial BW of 326 kgl. The ADG of steers fed
SORGHUM HYBRIDS AND PERFORMANCE OF RUMINANTS
cate grain samples. Tubes were thoroughly mixed to ensure that the sample was suspended. Another 5 mL of artificial saliva was used to rinse DM from the sides of the tube. Tubes were gassed with C02, stoppered with a one-hole (-1 mm in diameter) stopper, and placed in a 39°C water bath. Tubes were swirled midway during the incubation. Fermentation was terminated at 9 h by adding 1.5 mL of 3.6 M HC1 to each tube. Starch remaining in digested samples was measured as described previously except for the following modifications. All reactions were carried out in centrifuge tubes. After incubation at 3 9 O C, pH of the samples was adjusted to 5.0 with NaOH and 12.5 mL of 1.0 M sodium acetate buffer (pH 5.0) was added to each tube. Tubes were centrifuged for 2 20 min a t 1,500 x g before filtering. The IVSD was calculated by dividing the amount of starch remaining after incubation by the length of incubation. Preliminary experiments indicated that 9 h was in the linear portion of IVSD of sorghums (Figure 1). The values are an average of replications conducted on four different days. A second set of hybrids (entirely different from the 48 hybrids mentioned above) consisted of 17 experimental (not released commercially) hybrids grown for livestock feed and three hybrids grown for human consumption. These hybrids were assayed for IVSD as before except that samples were incubated for 4, 8, 12, 16, and 24 h, and fermentation was terminated by addition of 15 mL of cold (4OC) 1.0 M sodium acetate buffer (pH 5.0) with .2% (wt/voll benzoic acid. The pH of samples did not need to be adjusted with NaOH and no additional buffer was added. The IVSD was calculated by regressing the natural log of percentage of starch remaining in the sample against incubation length. The slope of the regression line represents fractional rate of starch disappearing per hour. Rate values were a n average of replications conducted on three different days. The 17 hybrids (including a bird-resistant hybrid) for livestock consumption were grown under nonirrigated conditions in the same location in eastern Nebraska. The other three hybrids were raised in a nursery with limited irrigation. Crude protein was calculated as total N (Kjeldahl method, AOAC, 1984) multiplied by 6.25. Correlation coefficients of grain composition were calculated using Pearson’s correlation coefficients (SAS, 1985). In this second in vitro experiment, ruminal fluid inoculum was prepared by obtaining aliquots of whole ruminal contents from two steers maintained on a n 80% concentrate diet. The concentrate portion was composed of dryrolled corn and supplement. Ruminal contents were strained through eight layers of cheesecloth and liquid
Downloaded from https://academic.oup.com/jas/article-abstract/70/9/2866/4705197 by Iowa State University user on 10 January 2019
fines, cracked berries, and foreign material. The grain was ground to pass a 1-mm screen in a cyclone-type grinder. Samples were stored at room temperature. Analysis of IVSD was conducted after both years’ samples were obtained. Starch in grain samples was determined as alinked glucose polymers by a modified MacRae and Armstrong (1968) procedure. A .5-g sample of cleaned, ground grain was weighed into a 125-mL Erlenmeyer flask. The sample was suspended in 50 mL of .5 M sodium acetate buffer (pH 5.0) and 100 pL of heat-stable a-amylase (Termamyl 120L, #TC-1000-2436, Fisher Scientific, Pittsburgh, PA) was added. Samples were autoclaved at 121OC for 30 min and a n additional 100 pL of heat-stable a-amylase was added. Flasks were then placed into a boiling water bath for 1 h. Samples were allowed to cool to 5 60°C. Any DM apparent on the sides of the flask was scraped back into the buffer-enzyme solution with a rubber policeman. When flasks had cooled sufficiently, 3 mL of a n amyloglucosidase (#A 7255, Sigma Chemical, St. Louis, M01 solution (250 units/mLl was added and the samples were incubated for 24 h a t 60°C. The suspensions were filtered through fast qualitative filter paper (#410, Schleicher & Schuell, Keene, NH) into 100-mL volumetric flasks. Samples were brought to volume with . 2 O/O (wt/vol) added benzoic acid to inhibit microbial growth in the samples. An aliquot was stored at 4 O C until analysis for glucose was conducted using a n automated procedure (Technicon Instruments Corp., Tarrytown, NY). Starch content was calculated by multiplying the glucose concentration by .9. Rate of starch disappearance was measured by incubating a .5-g sample of grain, cleaned and ground as before, in ruminal fluid. The sample was weighed into a 50-mL polypropylene centrifuge tube. Ruminal fluid inoculum was prepared by obtaining aliquots of whole ruminal contents from two steers One steer was maintained on a 90% concentrate diet. The concentrate portion was composed of dryrolled corn and supplement. The other donor steer was fed alfalfa hay. Ruminal contents were strained through eight layers of cheesecloth and the liquid from each animal was mixed in equal proportions into a warmed Thermos flask. The ruminal fluid was allowed to settle for approximately 10 min before being mixed (1 part grain inoculum: 1 part alfalfa inoculum; 2 parts warm [3Q0C1 artificial saliva [McDougall, 19481 to which 1 g/L urea had been added) and gassed with C02. The mixture was poured into separatory funnels, gassed with COz, and placed in a 39OC water bath for 2 20 min to remove settled and floating material from the inoculum. Fifteen milliliters of inoculum was added to dupli-
2867
2868
WESTER ET AL.
1977). 2.0
''
0
I
I
I
I
I
5
10
15
20
25
'0 30
Incubation time, h
Figure 1. Relationship of average starch remaining across 20 hybrids (after natural logarithmic transformation; * ) and extent of starch disappearance ( 0 )to length of incubation.
from each animal was mixed in equal proportions into a warmed thermos. Ruminal fluid was allowed to settle for approximately 10 min before being mixed in a 2:1 ratio with warm (39°C) artificial saliva (McDougall, 1948) to which 1 g/L of urea had been added and gassed with C02. For comparison of hybrids on the basis of IVSD, analysis of variance was performed using the GLM procedure of SAS (1985) using hybrid, year (in the case of the 48 hybrids), and incubation as independent variables. The hybrid x replication interaction provided the error term. Duncan's multiple range test (protected by a significant F test of P < .10 for hybrid) was used to compare means. To examine the effect of increasing amylopectin content on IVSD, three genetically similar hybrids differing in genes for amylopectin content were tested. A waxy hybrid CATx630 x RTx33381, a heterowaxy hybrid (ATx630 x RTx4351, and a nonwaxy hybrid CATx631 x RTx435) were grown in 1987 at Halfway, TX and characterized as having a white pericarp and heteroyellow endosperm (except for the waxy hybrid, which had a waxy endosperm; grain samples were generously provided by L. w. Rooney, Texas A&M University). The endosperm of the heterowaxy hybrid was phenotypically approximately 25% waxy. The waxy hybrid was openly pollinated so it was only about 95% waxy (L. W. Rooney, personal communication). The IVSD, using five incubation times (4, 8, 12, 16, and 24 h), was determined and statistical analysis performed as previously described except that values represented replications on two different days.
Steer Trial. Ten hybrids (five of the fastest and five of the slowest) of the original 48 were chosen for further in vitro evaluation using five incubation times to determine the starch degradation rate constants (data not shown). Based on rankings of the starch degradation rate constants, and availability of seed (some of the hybrids we wanted to grow for animal experiments were no longer commercially available), two hybrids from the fast group and two from the slow group were selected for planting to generate grain for animal trials. A feedlot trial was conducted to evaluate the effect of IVSD on the finishing performance of
Table 1. Composition of final diets in steer finishing Trial la Grain sorghumb Ingredient
A
B
80.00 5.00 5.00 5.00 2.04 1.35
5.00 5.00 1.90
.46
.46
.31 .30 .16 .10 .10
.45 .30 .16
.09
.09 .OS
C
D
80.00
80.00
80.00
5.00
5.00 5.00
YO
Sorghum Corn silage Alfalfa hay Molasses Feather meal Limestone Urea Finely ground corn Salt Potassium chloride Ammonium sulfate Fat Dicalcium phosphate Trace mineral premixC Vitamin premixd Monensin premixe Tylosin premixf
.05 .01 .02
.01
1.35
.10 .10
.o 1 .02
.o 1
5.00
-
5.00 5.00 5.00
1.59
.10 .10
1.35 .46 .74 .30 .17 .10 .10
.14
.10
.05 .01
.05 .01
.02 .01
.01
1.34 .46 2.30
.30 .17
.02
*Dry matter basis. bGrain sorghum hybrids: A was the hybrid with the fastest in vitro rate of starch digestion (IVSDI (6.95%/h), hybrid D had the slowest IVSD (6.48%/hI, and B and C were intermediate (6.75 and 6.640/o/h, respectively]. CTracemineral premix contained 13.0 to 15.0% Ca, 12.0% Zn, 8.0% Mn, 10.0% Fe, 1.5% Cu, .2% I, and .lob Co. dVitamin premix contained 30,000 IU/g of vitamin A, 6,000 IU/g of vitamin D, and 7.5 IU/g of vitamin E. eMonensin premix 132 g/kg. fTylosin premix 88 g/kg.
Downloaded from https://academic.oup.com/jas/article-abstract/70/9/2866/4705197 by Iowa State University user on 10 January 2019
The effect of removing tannins from a hightannin Bird-resistant) hybrid was studied by measuring IVSD of pearled grain, Samples of grain were pearled until approximately 25%, by weight, of the grain had been removed (Chibber et al., 1978). Pearled and unprocessed grains were evaluated by incubating samples for five incubation times (4, 8, 12, 16, and 24 h). Tannins were measured as catechin equivalents by the vanillinhydrochloric acid method (Guiragossian et al.,
SORGHUM HYBRIDS AND PERFORMANCE OF RUMINANTS
Table 2. Composition of diets in lamb finishing Trial 2a Grain sorghumb Ingredient
A1
A
D
BR
72.00
72.00
20.00
2.00 3.00
YO
Sorghum Finely ground alfalfa hay Molasses supplementC Limestone Molasses Feather meal Finely ground corn
72.00 20.00 3.00 .50 4.00
.40 .10
72.00 20.00 3.00 .SO 3.36 1.14
-
3.00 .50 4.00
.SO
.50
3.21 1.29
-
*DM basis. bGrain sorghum hybrids: A1 was the hybrid with the fastest in vitro rate of starch digestion (IVSD) (6.83%/h), hybrid D had the slowest IVSD (6.24%/h),and A and BR were intermediate (6.60 and 6.31%/h, respectively). Hybrids A and D were also used in the steer trial and BR was a high-tannin hybrid. CSupplement was based on molasses and urea liquor and contained on a dry matter basis 50.6% crude protein, 2.61% K, 2.25% Fe, 1.0% Zn, .95% Ca, .64% Mn, .55% I, .55% P, . 4 1 % S, 3 5 % Mg, .20% Cu,.16% Co, 16,287IU of vitamin A/kg, 3258 IU of vitamin D/kg, and 4 IU of vitamin E/kg.
NE. Lambs had free access to water. Three lambs were removed from the study because of illness and were not included in cumulative measurements. Lambs were adjusted to a d libitum intake with incremental increases (.28% of BW) made every 2 d in the amount of feed offered. Most lambs had achieved ad libitum intake within 20 d. Diets were fed once daily for a total of 85 d. Feed samples and orts were collected weekly for DM analysis. In addition to grain sorghum, the diets contained 20% finely ground (to pass a 12.5-mm screen) alfalfa hay, 3% molasses-urea liquor-based supplement (50.6% CP), and .5% limestone. The remaining 4 . 5 % of the diet DM was derived from feather meal, molasses, and finely ground corn (to pass a 6.4 mm-screen). Diets were formulated (DM basis) to contain 12.8% CP, .6% Ca, . 4 % P, and .8% K. Initial and final BW were the average of weights taken on three consecutive days during which, and including 1 d prior, lambs were fed a constant percentage of BW to minimize differences in gut fill. Analysis of variance of lamb performance was conducted as outlined by Steel and Torrie (1980) for a randomized complete block design with block and treatment as main effects and residual as the error term. Least squares means and lsd were computed using the GLM procedure of SAS (1985). The IVSD of grain hybrids fed to lambs, grown in 1988, was determined and analyzed as described previously for the steer trial. Performance of the steers and lambs was correlated to IVSD by calculating simple correlation coefficients between treatment means and IVSD.
Downloaded from https://academic.oup.com/jas/article-abstract/70/9/2866/4705197 by Iowa State University user on 10 January 2019
steers. Selected hybrids were grown in 1988 at the University of Nebraska Agricultural Research and Development Center a t Mead, NE and were fed dry-rolled at 80% of the final dietary DM (Table 1) to 128 mixed crossbred steers (mean initial BW of 326 k 9 kg) allotted randomly to four treatments. Each treatment was replicated in four pens. Steers were housed in 3.7-m x 6.1-m pens within a threesided barn with southerly exposure and were allowed free access to water. Steers were allowed a d libitum access to feed for a total of 133 d starting on December 15, 1988, and ending on April 28, 1989. Steers were adapted to the final diets by adjusting roughage levels from 71, 57, 45, and 25% (corn silage-alfalfa mixture) for 3, 3, 7, and 7 d, respectively. All diets were fed once daily and formulated (DM basis) to contain .70% Ca, .35% P, .70% K, 27.5 mg/kg of monensin (Elanco Products, Indianapolis, IN), and 11.0 m g k g of tylosin (Elanco Products). Final diets were formulated (DM basis) to contain 13.1% CP, because this was the amount of protein present in the nonprotein supplemented diet that consisted of the hybrid with the highest CP (Diet C). Feather meal was used in the other diets to balance to 13.1% CP. The remaining 20% of the dietary DM was derived equally from corn silage, alfalfa hay, molasses, and supplement. Steers were implanted with estradiol-17p (Elanco Products). Initial weight was the average of weights taken on two consecutive days, and final weight was estimated by adjusting the hot carcass weight to a 62% dressing percentage. Hot carcass weight and liver score (incidence and severity of liver abscesses) were recorded a t time of slaughter, and 12th rib fat thickness and quality grade were measured after a 48-h chill. The IVSD of the grain hybrids fed to the steers, produced in 1988, was determined and analyzed as described previously using five incubation times. Analysis of variance of steer performance and carcass characteristics was performed as outlined by Steel and Torrie (1980) for a completely random design. Least squares means and lsd were computed using the GLM procedure of SAS (1985). Lamb Trial. Four grain sorghum hybrids, including Hybrids A and D from Trial 1, a bird-resistant hybrid, and a hybrid with an IVSD similar to that of Hybrid A were grown at the University of Nebraska Agricultural Research and Development Center a t Mead, NE in 1988. Hybrids were dry-rolled and fed as 72% of the dietary DM (Table 2) to mixed crossbred finishing lambs (mean initial BW of 28 f 2 kg) in a randomized complete block design. Forty lambs (24 wethers and 16 ewes) were assigned to 10 blocks according to weight and sex and were assigned randomly to individual pens (.84 m21 in the Animal Science Complex, Lincoln,
2869
WESTER ET AL.
2870
Results and Discussion
1980).
Downloaded from https://academic.oup.com/jas/article-abstract/70/9/2866/4705197 by Iowa State University user on 10 January 2019
Grain sorghum hybrids evaluated in these studies were chosen from University of Nebraska hybrid testing for the 48 varieties. Hybrids selected for the steer trial were selected from this initial screening. The second group of hybrids tested for IVSD were experimental hybrids that were not released for commercial use and were grown in the same year and most of them in the same location. None of the hybrids in the 48-sample test was present in the second group of hybrids. The second group of hybrids and the 48 hybrids used in the initial study and the animal trials were grown in different years. Labovatory Evaluation. The IVSD values of the hybrids ranged from 5.2 to 6.3%/h (Table 3). Hybrids with the nine fastest IVSD values were different from hybrids with the two slowest (P e .05). Hybrid IVSD was affected by year and replication (P c .01; data not shown), but no interaction between hybrid and year was observed. Significant replication variation suggests that IVSD values should not be taken as absolute, but rather as relative, values within a series of incubations. Therefore, IVSD values presented in our paper should be viewed in that context. The IVSD values reported within each table in our paper were run simultaneously and can be compared; however, IVSD values reported in different tables were during different incubations home in different years), and absolute values should not be compared. Lack of a n interaction between hybrid and year suggests that selection or ranking of hybrids could be made based on IVSD. Among the 48 hybrids tested, total starch content ranged from 64.3 to 70.3% of DM (P c .01, Table 3). Hibberd et al. (1979b) demonstrated that starch content varied among eight selected grain sorghum genotypes from 66.6 to 79.5%. Starch content of the hybrids also differed (P e .01) between growing years, indicating that environmental factors affect starch content. Bach Knudsen et al. (1987a,b) found that DE and starch content of different varieties of barley were affected by year and location grown, although there was no interaction between variety and year. These authors also determined that differences existed within a varietal type in response to year and location. Goldy et al. (1986) examined 15 hard red winter wheat varieties and concluded that for many quality variables, differences were greater for location than for variety. Hibberd et al. (1980) indicated that for grain sorghum hybrids in their study, CP was affected by a hybrid x location interaction, whereas starch content was not. Also, IVDMD was affected by location (Hibberd et al.,
In our second set of hybrids compared, the two hybrids with the fastest IVSD values were different (P c .lo) from the six hybrids with the slowest rates (Table 4). Hybrids used for human consumption ranked first (9.l%/hl, sixth (7.7%/h), and eighteenth (6.7%/h) in the overall comparison. Food hybrids all had a cream-colored pericarp, a trait that is used to improve the aesthetic quality of flour. The average disappearance curve for starch across hybrids was linear when amount of starch remaining, after natural logarithmic transformation, was plotted against incubation time (R2= ,961, Figure 1). Galyean et al. (19811 observed that starch disappearance in corn, in situ, consisted of a rapidly ( e 2 h) degraded fraction, after which starch disappeared at a slower rate. A rapidly degraded starch fraction was not apparent in our data. Total starch and CP content of the grain were not related to IVSD Ir = .094, P = .69 and r = .047, P = .84, for starch and CP, respectively). Taylor et al. (1984) reported that increased protein content of sorghum grain increased the prolamin fraction (endosperm storage proteins). This report suggests that a hybrid with high CP may have a lower IVSD if the relationship between prolamins and starch digestion is negative. No clear evidence exists linking prolamin content and starch digestibility of grain; however, Sullins and Rooney (1974) speculated that prolamins reduced starch availability in sorghums. Chandrashekar and Kirleis (1988) pointed out that increased sorghum grain protein is related to increased numbers of prola min-rich protein storage bodies. The increased amount of protein bodies present may result in denser and thicker peripheral and vitreous endosperms, which could make starch present in those layers and within the floury endosperm less available to enzymatic degradation. Our results do not support this hypothesis. Similarly, the lack of correlation between CP and percentage of vitreousness reported by Cagampang and Kirleis (1984) also does not support this hypothesis. Among hybrids studied by Cagampang and Kirleis (19841, starch and CP content were not correlated. Chandrashekar and Kirleis (19881 also reported no correlation of starch and protein. Some of the similarity observed in IVSD among hybrids is likely the result of close genetic relationship. Parental cultivar crosses of commercial hybrids are not publically known and there may be, in fact, only a small number of parental cultivars actually used in commercial hybrid production IB. E. Johnson, USDA grain geneticist, Lincoln, NE, personal communication). Therefore, hybrids with similar IVSD may be closely related genetically.
2871
SORGHUM HYBRIDS AND PERFORMANCE OF RUMINANTS
We evaluated the next group of hybrids, which varied in the waxy gene, because they were closely related genetically and were grown a t the same location in the same year. Although we did not measure amount of amylopectin in these samples, different genotypes are known to produce differ-
ences in grain amylopectin content. Therefore, this was a n opportunity to examine effects of the different waxy gene hybrids on IVSD. The waxy hybrid had the fastest IVSD value, whereas the nonwaxy had the slowest IVSD, and the heterowaxy IVSD was intermediate (Table 51. Differ-
Table 3. Rank of 48 test hybrids by nine-hour in vitro starch digestion
1 2 3 4 5 8 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 38 37 38 39 40 41 42 43 44 45 48 47 48
SE
N
Total starch, % & 68.4 64.3 66.6 87.7 67.3 86.9 88.5 67.1 89.1 68.5 68.4 66.3 65.3 66.9 68.9 67.7 66.4 66.3 65.8 67.8 87.8 68.0 69.8 70.3 65.2 66.7 66.6 66.0
65.5 66.9 69.0 64.3 66.8 68.0 68.3 67.3 68.5 66.1 67.6 67.9 66.8 66.1 68.8 87.8 86.7 67.3 65.0 69.5 .57 4
IVSD~ 6.3 6.1 6.1 8.1 6.0 5.9 5.9 5.9 5.9 5.8 5.8 5.8 5.8 5.8 5.8 5.7 5.7 5.7 5.7 5.7 5.8 5.8 5.8 5.8 5.8 5.8 5.8 5.8 5.8 5.8 5.8 5.5 5.5 5.5 5.5 5.5 5.5 5.5 5.5 5.5 5.4 5.4 5.4 5.4 5.4 5.4 5.3 5.2 .l8 4
Extent of starch disappearance, % 56.3 55.2 54.7 54.4 53.8 53.1 53.1 53.0 52.9 52.2 52.2 52.2 51.9 51.8 51.8 51.7 51.8 51.4 51.2 51.0 50.6 50.6 50.8 50.6 50.5 50.3 50.3 50.2 50.1 50.0 50.0 49.9 49.7 49.6 49.5 49.4 49.3 49.1 49.1 49.0 48.9 49.8 48.7 48.6 48.3 48.3 47.7 47.2 1.44 4
IVSD Duncan’s groupingC A A A A A A A A A A A A A A A A A
B B C B C D B C D E B C D E F B C D E F B C D E F B C D E F B C D E F G B C D E F G B C D E F G B C D E F G B C D E F G B C D E F G B C D E F G B C D E F G B C D E F G B C D E F G B C D E F G B C D E F G B C D E F G B C D E F G B C D E F G B C D E F G B C D E F G B C D E F G B C D E F G C D E F G C D E F G C D E F G C D E F G C D E F G D E F G D E F G D E F G E F G E F G E F G E F G E F G E F G E F G E F G F G F G G G
-
&Dry matter starch content of whole, cleaned grain. bIVSD = in vitro rate of starch disappearance expressed in percentage of starch portion disappearing per hour. The values are an average of replications conducted on four different days. CDuncan’smultiple range test performed on IVSD. Hybrids without common letters differ ( P < .05).
Downloaded from https://academic.oup.com/jas/article-abstract/70/9/2866/4705197 by Iowa State University user on 10 January 2019
Grain sorghum hybrid
WESTER ET AL.
2872
Table 4. Characteristicsa of grain sorghum hybrids used for in vitro Trial 2
Hybrid
Pericarp color
Starch, 016
IVSDb
~
ld 2
3 5 gd
7 8 9
10 11 12 13 14 15 16 17 18d 19 20e SE n
9.1 9.1 8.7 8.5 7.7 7.7 7.6 7.5 7.5 7.3 7.2 7.2 7.1 7.0
66.6
66.5 67.9 67.9 68.8 71.0 70.2 71.0 70.9 67.3 71.6 69.5 69.5
6.9
6.9 6.8 6.7 6.6 6 .O
66.6
1.25 2
-
YO
~
68.5 70.4 71.0 69.3 68.7 68.5
-
CP,
IVSD Duncan's groupingC
.60
3
87.1 86.1 85.5 85.1 83.4 83.1 81.1 83.6 82.7 81.1 82.8 82.8 81.8 81.1 80.6 81.1 80.6
79.0 77.9 75.8 1.99 3
10.4
11.0 11.8 9.5 11.5
10.3 12.1 11.6 10.9 11.3 11.5 12.0 11.5 11.3 10.8 10.6 10.7 9.3 10.8 11.5 .07 2
A A A A A A A A A
B BC B C D B C D BCD BCD BCD B C D B C D B C D B C D B C D C D C D C D D D D
-
-
*Dry matter basis. bIVSD = in vitro rate of starch disappearance expressed as the fractional rate of starch disappearing per hour. The values are an average of replications conducted on three different days. CDuncan's multiple range test performed on IVSD. Hybrids without common letters differ (P < ,101. dGrain sorghum grown for human consumption. eBird-resistant, high-tannin sorghum.
ences observed in IVSD among hybrids should have resulted only from differences in genotype of the hybrid. Differences observed among IVSD values of the waxy, heterowaxy, and nonwaxy hybrids were predictable considering the changing composition of starch in the grains. Amylopectin, the primary component [ > 95%) of waxy starches, is more susceptible to enzymatic degradation than are normal starches (Rooney and Pfugfelder, 19861.
Hibberd et al. (1979b)observed that waxy sorghum grain had the greatest IVDMD and in vitro gas production. Streeter et al. (1990a) reported similar results. The IVSD data presented here represent the only comparison of genetically similar hybrids differing primarily in waxiness of the starch. It is plausible that the increase in amylopectin concentration was partially responsible for the increase in IVSD observed; however, other factors (not
Table 5. Characteristicsa of grain sorghum hybrids differing in degree of waxiness
Hybrid ATx630 x RTx3338 ATx630 x RTx435 ATx631 x RTx435 SE n
Endosperm type
CP,
Starch,
%
%
IVSDbC
Waxy Heterowaxy Nonwaxy
1.3 12.1 11.2 .07
73.7 71.6 72.3 .75
8.2 7.7 7.2 .13 2
-
2
2
Extent of starch disappearance at 24 h, % 85.1 82.0 79.4
1.61 2
*Dry matter basis. n = 2. bIVSD = in vitro rate of starch disappearance expressed as the fractional rate of starch disappearing per hour. The values are an average of replications conducted on two different days. CContrasts:waxy vs heterowaxy, P = .11; waxy vs nonwaxy, P = .03; heterowaxy vs nonwaxy, P = .12.
Downloaded from https://academic.oup.com/jas/article-abstract/70/9/2866/4705197 by Iowa State University user on 10 January 2019
4
Cream Bronze Bronze Cream Bronze Cream Bronze Bronze Bronze Bronze Bronze Bronze Cream Bronze Red Bronze Cream Cream Cream Bronze
Extent of starch disappearance at 24 h, Oh
SORGHUM
HYBRIDS AND PERFORMANCE OF RUMINANTS
2873
Table 6. Effect of pearling on the characteristicsa of high-tannin grain sorghum
CP,
Starch,
To b
%
010
Unprocessed Pearled SE n
4.84 .62
9.6 8.4 .04 2
2
69.5 80.5 .76 3
.
IVSDC 5.3 5.8 .31 5
72.9 76.8 1.52 5
&Dry matter basis. bExpressed on a DM basis as catechin equivalents. CIVSD = in vitro rate of starch disappearance expressed as the fractional rate of starch disappearing per hour. The values are a n average of replications conducted on five different days.
measured) that could change with different genotypes of the hybrids may also have been responsible for changes in IVSD. Because one of the hybrids used in the sheep trial was bird-resistant, we wanted to know whether the tannins in the grain affected IVSD. Removing 25% of the weight of the grain by pearling resulted in removal of just over 87% of the tannin (as measured by catechin equivalents; Table 6). The IVSD of pearled grain did not differ from that of unprocessed grain (P = .331, suggesting that the materials removed by pearling were not responsible for the reduced IVSD observed with bird-resistant hybrids. Level of catechin equivalents in the pearled grain was 120 to 700% greater than that found in low-tannin hybrids (Chibber et al., 1978; Taylor et al., 19841. Chibber et al. (1978)were able to remove 74.6% of the tannins when 24.6% of the weight of a high-tannin hybrid was removed by pearling. When 37% of the weight was removed, only 2.4% of the tannin remained; the most tannin removed by pearling was 98%. Bird-resistant hybrids have been reported to be less digestible than hybrids
with low tannin content (Hibberd et al., 1979a, 1982a; Streeter et al., 1986). Possibly, tannin remaining in the grain after pearling was sufficient to cause reduced enzymatic activity and suppress starch digestion. Streeter et al. (1990~1reported a tendency (P = ,131 for ruminal starch digestibility to be greater for bird-resistant hybrids than for a waxy counterpart or a millrun sorghum. Tannin is only one of the polyphenols associated with birdresistant sorghums and is not directly measured by the vanillin-HC1 method commonly used to determine tannin content (Daiber, 1975). Therefore, whether tannins (polyphenols) were not sufficiently removed to reduce their negative effect on enzyme activity or whether there are other factors inherent in the grain that limited enzyme activity (or otherwise caused decreased IVSD) could not be distinguished in our study. Animal TriaZs. Differences in steer performance were observed primarily when we compared the steers fed Hybrid A, which had the fastest IVSD, to those fed Hybrid D, which had the slowest IVSD (Table 7). Steers fed A had 9.0% faster ADG than steers fed D (P = .06).No treatment differences
Table 7. Effect of sorghum hybrid on steer performance and carcass characteristics Grain sorghum Item Grain IVSD, % / h a DMI, kg/d ADG, kg Gain/feed Liver scoree 12th rib fat, mm Quality gradef
A ?.Ob 9.92 1.33b .135 .09 12.57 18.66
B 6.8' 9.48 1.24bC ,131 .12 11.43 18.76
C 6Bcd 10.07 1.30bC ,129 .03 12.19 18.62
D 6.5d 9.57 1.22c .128 .09 11.37 18.25
SE .07 .23 .04 .004 .06 .OB
.19
'IVSD = in vitro rate of starch disappearance expressed as the fractional rate of starch disappearing per hour. The values are a n average of replications conducted on three different days. b,c,dWithin rows, values without common superscripts differ (P c .lo). eLiver score: 0 = healthy liver, 1 = one or two small abscesses, 2 = two to four active abscesses, 3 = one or more large abscesses, 4 = adherence of abscess to diaphragm or gut. fQuality grade: Choice = 19, Select+ = 18, Select" = 17.
Downloaded from https://academic.oup.com/jas/article-abstract/70/9/2866/4705197 by Iowa State University user on 10 January 2019
Tannin, Sample
Extent of starch disappearance at 24 h, %
2874
WESTER ET AL.
,136
,134
I
1.215
I
A
.210
R2= .94
.195
5
Q (D
(D
.I90
6.2
,180
6.4
6.6
6.8
7.0
In vitro starch disappearance,%/h
Figure 2. Relationship of in vitro starch disappearance to gain:feed in cattle (- W -1 and lamb (- - A - -] trials.
were observed in gain:feed, DMI, liver score, 12th rib fat thickness, or quality grade among treatments; however, simple correlations of the means of gain:feed IVSD revealed a strong (R2 = .94) relationship (Figure 2). A similar relationship between IVSD and gain:feed when different grain sorghum processing methods were evaluated was reported by Stock et al. (1987). In the sheep trial, none of the IVSD values for hybrids differed, but the relationship between Hybrid A and Hybrid D was similar to the data obtained on the same hybrids for the steer trial (Table 8). Overall, there were no differences CP > .lo) for DMI and ADG for lambs among the four hybrids. Lambs fed A were more efficient (gain: .05). The feed) than lambs fed A1 and BR (P hybrid (All with the fastest (numerically) IVSD also resulted in the lowest gain:feed. The possibility that subacute acidosis caused reduced performance of lambs fed A1 does not seem likely because intake was not reduced, a common sign of acidosis (Britton and Stock, 1986).
Table 8. Effect of sorghum hybrid on lamb performance Grain sorghum Item Grain IVSD,%/ha DMI, g/d ADG, g
Gain/feed
6.6 1,305 289 .2lOb
0.2 1,365 281 .200bC
6.8 1,363 273
.VMc
6.3 1,377 274 .188C
.26 38.1 12.5 ,008
&IVSD = in vitro rate of starch disappearance expressed as the fractional rate starch disappearing per hour. The values are an average of replications conducted on three different days. .101. b*cWithinrows, values without common superscripts differ (P
Downloaded from https://academic.oup.com/jas/article-abstract/70/9/2866/4705197 by Iowa State University user on 10 January 2019
// 1: 9 I - - _._
,126
Although steer efficiencies were related to IVSD, efficiencies from the lamb trial exhibited no relationship (Figure 2). We expected that gainfeed would be positively correlated with ruminal digestibility of sorghum and, therefore, to IVSD. Mertens and Ely (1982) reported that feed digestibility by lambs was less than that by cattle when digestibilities were c 66% and greater by sheep than by cattle when digestibilities were > 66%. One explanation for the lack of difference observed in our lamb trial may be that lambs are less sensitive to changes in IVSD because of their greater inherent digestibility of highly digestible feeds. Lambs fed the high-tannin BR did not perform as well as those fed A and D. Bird-resistant sorghums have lower digestibilities and result in decreased animal performance compared with low-tannin hybrids (Rooney and Pflugfelder, 1986). We have no explanation for the relationship between the performance of lambs fed BR and those fed A1. Broilers fed Hybrid A1 had 12.1% greater ME intake and greater weight gain and efficiency than broilers fed the BR hybrid (Douglas et al., 1990a). This resulted in the same rate of gain and efficiency of birds fed A1 as those fed a corn-based control diet (Douglas et al., 1990b). Previous studies have dealt mainly with in vitro assessment (Hibberd et al., 1979b, 1982b; Streeter et al., 1990a) or in vivo digestibility (Hibberd et al., 1983; Streeter et al., 1990b, 1991) of divergent lines of grain sorghum. McCollough et al. (1972a1 compared the feedlot performance of cattle fed eight grain sorghum hybrids and found that differences existed among hybrids with similar kernel characteristics. They found a > 10% difference in feed efficiency among hybrids with the same endosperm type (yellowl. Carcass characteristics did not differ among steers fed different hybrids. No correlation was evident between feed efficiency and in vitro gas production (McCollough, 1972). Hybrids in the studies of McCollough (1972) were grown under similar conditions; thus, differences observed in performance of steers fed those hybrids could have been directly attributed to genetic variation that existed among those
SORGHUM HYBRIDS AND PERFORMANCE OF RUMINANTS
Implications Our research illustrates that variability in in vitro starch digestion exists among commercially available grain sorghum hybrids, and this variability may affect cattle performance. In vitro starch disappearance, as an index of ruminally available starch, may be a useful selection criterion in a breeding program designed to increase the value of minimally processed sorghum grain. The lamb trial showed, however, that increased rate of ruminal starch digestion is not an absolute predictor of animal performance and that other factors can affect performance of finishing ruminants.
Literature Cited AOAC. 1984. Official Methods of Analysis (14th Ed.).Association of Official Analytical Chemists, Arlington, VA. Bach Knudsen, K.E.B.. P. Aman, and B. 0. Eggum. 1987a. Nutritive value of Danish-grown barley varieties. I. Carbohydrates and other major constituents. J. Cereal Sci. 6:173. Bach Knudsen, K.E.B.,P. Aman, and B. 0. Eggum. 1987b.Nutritive value of Danish-grown barley varieties. 11. Effect of carbohydrate composition on digestibility of energy and protein. J. Cereal Sci. 6:187. Britton, R. A,, and R. A. Stock. 1986. Acidosis, rate of starch digestion and intake. In: F. N. Owens (Ed.) Symposium Proceedings: Feed Intake by Beef Cattle. p 125. Oklahoma Agric. Exp. Sta. MP-121. Cagampang, G. B., and A. W. Kirleis. 1984. Relationship of sorghum grain hardness to selected physical and chemical measurements of grain quality. Cereal Chem. 65:lOO. Chandrashekar, A., and A. W. Kirleis. 1988. Influence of protein on starch gelatinization in sorghum. Cereal Chem. 65:457. Chibber, B.A.K., E. T. Mertz, and J. D. Axtell. 1978. Effects of dehulling on tannin content, protein distribution and quality of high and low tannin sorghum. J. Agric. Food Chem. 26579. Daiber, K. H.1075. Enzyme inhibition by polyphenols of sorghum grain and malt. J. Sci. Food Agric. 26:1399. Douglas, J. M., T. W. Sullivan, P. L. Bond, and F. J. Struwe. 199Oa. Nutrient composition and metabolizable energy values of selected grain sorghum varieties and yellow corn. Poult. Sci. 69:1147. Douglas, J. M., T. W. Sullivan, P. L. Bond, F. J. Struwe, J. G. Baier, and L. G. Robeson. 1990b. Influence of grinding, rolling, and pelleting on the nutritional value of grain SOT. ghums and yellow corn for broilers. Poult. Sci. 69:2150. Galyean, M. L., D. G. Wagner, and F. N. Owens. 1981. Dry
matter and starch disappearance of corn and sorghum as influenced by particle size and processing. J. Dairy Sci. 64: 1804. Goldy, G., J. Riley, G. Posler, A. Lenssen, and T. Walters. 1986. Effect of variety, location and irrigation on selected criteria for evaluating wheat as a feed for ruminants. p 1. Kansas State Univ. Cattlemen’s Day Report. Gramlich, S. M. 1988. Grain hybrids and starch utilization in ruminants. M.S. Thesis. University of Nebraska, Lincoln. Guiragossian, V. Y.,S. W. Van Scoyoc, and J. D. Axtell. 1077. Chemical and Biological Methods for Grain and Forage Sorghum. Dept. of Agronomy, Agric. Exp. Sta., Purdue Univ., West Lafayette, IN. Hibberd, C. A., R. L. Hintz, and D. G. Wagner. 1980. The effect of location on the nutritive characteristics of several grain sorghum hybrids. Anim. Sci. Res. Rep., Oklahoma Agric. Exp. Sta. MP-107:102. Hibberd, C. A., E. D. Mitchell, D. G. Wagner, and R. L. Hintz. 1979a. Seed characteristics of different varieties of grain sorghum. Anim. Sci. Res. Rep., Oklahoma Agric. Exp. Sta. MP-104:16. Hibberd, C. A., D. G. Wagner, and R. L. Hintz. 1982a. Effect of stage of maturity on the chemical composition and in vitro digestibility of sorghum grain. Anim. Sci. Res. Rep., Oklahoma Agric. Exp. Sta. MP-112:178. Hibberd, C. A,, D. G. Wagner, R. L. Hintz, and D. D. Griffen. 1983. Effect of sorghum grain variety and processing method on the site and extent of starch digestion in steers. h i m . Sci. Res. Rep., Oklahoma Agric. Exp. Sta. MP-114:28. Hibberd, C. A,, D. G. Wagner, R. L. Schemm, E. D. Mitchell, Jr., R. L. Hintz, and D. E. Weibel. 1982b. Nutritive characteristics of different varieties of sorghum and corn grains. J. Anim. Sci. 55665. Hibberd, C. A,, D. E. Weibel, R. L. Hintz, and D. G. Wagner. 1979b. The influence of variety on nutritive characteristics of grain sorghum. Anim. Sci. Res. Rep., Oklahoma Agric. Exp. Sta. MP-104:12. MacRae, J. C., and D. G. Armstrong. 1968. Enzyme methods for determination of alpha-linked glucose polymers in biological materials. J. Sci. Food Agric. 19:578. McCollough, R. L. 1972. Nutritive value of eight hybrid sorghum grains and three hybrid corns compared in all-concentrate rations. Part I: Hybrid sorghum and corn characteristics and methods used to evaluate them. Kansas Agric. Exp. Sta. Bull. 557~15. McCollough, R. L., C. L. Drake, and G. M. Roth. 1972a. Nutritive value of eight hybrid sorghum grains and three hybrid corns compared in all-concentrate rations. Part 11. Feedlot performance of eight hybrid sorghum grains and three hybrid corns. Kansas Agric. Exp. Sta. Bull. 557:21. McCollough, R. L., J. G. Riley, C. L. Drake, and G. M. Roth. 1972b. Feedlot performance on nine hybrid sorghum grains fed to steers winter, 1971-1972. Kansas Agric. Exp. Sta. Bull. 557:37. McDougall, E. I. 1948. Studies on ruminant saliva. I. The composition and output of sheep’s saliva. Biochem. J. 43:99. Mertens, D. R., and L. 0. Ely. 1982. Relationship of rate and extent of digestion to forage utilization-A dynamic model evaluation. J. Anim. Sci. 54:895. IZlrskov, E. R. 1986. Starch digestion and utilization in ruminants. J. Anim. Sci. 63:1624. Rooney, L. W., and R. L. Pflugfelder. 1986. Factors affecting starch digestibility with special emphasis on sorghum and corn. J. Anim. Sci. 63:1607. SAS. 1985. SAS User’s Guide: Statistics. SAS Inst. Inc., Cary, NC. Sherrod, L. B., R. C. Albin, and R. D. Furr. 1969. Net energy of regular and waxy sorghum grains for finishing steers. J. Anim. Sci. 29:997. Steel, R.G.D., and J. H. Torrie. 1980. Principles and Procedures
Downloaded from https://academic.oup.com/jas/article-abstract/70/9/2866/4705197 by Iowa State University user on 10 January 2019
hybrids. Gramlich (1988) observed that lamb finishing performance was affected by sorghum hybrid. Lambs fed a grain sorghum hybrid selected on the basis of high forage digestibility after grain harvest had lower ADG and were more efficient than those fed a hybrid selected on the basis of low forage digestibility and two grain sorghum hybrids unselected for forage digestibility. Our in vitro data and animal performance trials indicate that rate of grain sorghum starch digestion may influence the feeding value of grain sorghum.
2875
2876
WESTER ET AL. and in vitro gas production of sorghum grain varieties. h i m . Sci. Res. Rep., Oklahoma Agric. Exp. Sta. MP-108:91. Streeter, M. N., D. G. Wagner, F. N. Owens, and C. A. Hibberd. 1991. The effect of pure and partial yellow endosperm sorghum grain hybrids on site and extent of digestion in beef steers. J. Anim. Sci. 00:2571. Stock, R. A,, D. R. Brink, K. K. Kreikemeier, and K. K. Smith. 1987. Evaluation of early-harvested and reconstituted grain sorghum in finishing steers. J. Anim. Sci. 65:548. Sullins, R. D., and L. W. Rooney. 1074. Microscopic evaluation of the digestibility of sorghum lines that differ in endosperm characteristics. Cereal Chem. 51:134. Taylor, J.R.N., L. Schussler, and W. H. van der Walt. 1984. Fractionation of proteins from low-tannin sorghum grain. J. Agric. Food Chem. 32:140.
Downloaded from https://academic.oup.com/jas/article-abstract/70/9/2866/4705197 by Iowa State University user on 10 January 2019
of Statistics: A Biometrical Approach (2nd Ed.). McGrawHill Book Co., New York. Streeter, M. N., D. G. Wagner, C. A. Hibberd, E. D. Mitchell, Jr., and J. W. Oltjen. 199Oa. Effect of variety of sorghum grain on digestion and availability of dry matter and starch in vitro. Anim. Feed Sci. Tech. 29:279. Streeter, M. N., D. G. Wagner, C. A. Hibberd, and F. N. Owens. 1990b. Comparison of corn with four sorghum grain hybrids: Site and extent of digestion in steers. J. Anim. Sci. 68:3420. Streeter, M. N., D. G. Wagner, C. A. Hibberd, and F. W. Owens. 1 9 9 0 ~ .The effect of sorghum grain variety on site and extent of digestion in beef heifers. J. Anim. Sci. 68:1121. Streeter, M. N., D. G. Wagner, C. A. Hibberd, F. N. Owens, and D. S. Buchanan. 1086. In vitro dry matter disappearance
