Influence of flake density on the comparative feeding value of steam-flaked corn for feedlot cattle.

R. A. Zinn'

University of California, El Centro 92243 ABSTRACT

Two trials were conducted to examine the influence of flake density (FD) on the feeding value of steam-flaked corn. Treatments consisted of corn that had been steam-flaked to mean densities of .42, -36 and .30 kg/liter (28, 24 and 20 lbbu). In Trial 1, treatment effects on characteristics of digestion were evaluated using three crossbred steers with cannulas in the m e n and proximal duodenum. In Trial 2, treatment effects on feedlot performance were evaluated in a 112-d finishing mal involving 72 crossbred steers with an average initial weight of 312 kg. Flake density was directly related to flake thickness (P < .01) and inversely related (P < .01) to in vitro enzymatic digestibility of starch. Decreasing the FD resulted in a linear decrease (P< .01) in ruminal pH and linear increases (P< .05) in postruminal and total tract digestibility of starch. Posmminal digestibility of N and total tract digestibility of OM, N and energy also increased linearly (P < .05) with decreasing FD. Flake density did not influence (P > .lo) feedlot performance or carcass merit. There was a tendency (P> .lo) for depressed rate and efficiency of gain for steers fed the 30 kgJ liter FD corn. Improvements in digestibility and N utilization of SF corn-based diets as a result of decreasing FD from .42 to .30 kgfliter did not enhance feedlot performance. This may be due to digestive dysfunction, perhaps related to processing effects on ruminal pH. (Key Words: Maize, Processing, Cattle, Metabolism.) J. h i m . Sci.

1990. 68:161-715

reflect extent of digestion or value. With barley, for example, in vitro rate of digestion Feedlot growth have shown that of starch increased linearly as fl decreased (13 to 16%) the energy (Osman et al., 1970). Yet, feedlot response to flaking value of corn over that of (ziM$ steam flaking barley generally has been nonthat significant (Garret, 1965; Male et al., 1966; 1987)* However* production processing remain Parrot et al., 1969). The objective of the adequately reflect undefined* Osrnan et (19'0) that present study was to evaluate the influence of flake density (FD)on the utilization of steams+ng.wi*out flaking.did not ?crew.* of (@soon by panmeam (30 mm) Of flaked (SF) corn by fedlot cattle. barley or sorghum starch. Flaking, on the other hand, greatly improved starch digestion of both ExperimentalProcedure barley and sorghum. The degree of increase was found to be linearly to the Trial I . Three crossbred steers (427 kg) thickness of the flake (FT).Such studies have with cannulas in the ,.,,men and suprted the that the thinner the duodenum (edge of the flange was approxithe better the be mately 6 cm from the pyloric sphincter) were of digestion may not used in a latin square experiment to evaluate However, Changes in the effects of FD on characteristics of digestion. Composition of the basal diet is shown in Table 1. A single chromic oxide premix was '~nim.Sei. Dept., ~mpcria~ V d e y ~ g r i cCenter. . used that contained all dietary ingredients Received March 15, 1989. except for SF corn processed as described Accepted June 23.1989.

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INFLUENCE OF FLAKE DENSITY ON THE COMPARATIVE FEEDING VALUE OF STEAM-FLAKED CORN FOR FEEDLOT CATTLE

768

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period were composited for analysis. During the final day of each collection period, ruminal samples were obtained from each steer approxItem Trial1 Trial2 imately 4 h postprandially. Ruminal fluid pH Ingredient composition. 96 was determined and, subsequently, 2 ml of Alfalfa hay 5.92 6.00 freshly prepared 25% (w/v) meta- phosphoric Sudangrass hay 5.92 4.00 acid was added to 8 n=ml of strained ruminal Steam-flakedcorn 75.01 80.17 fluid. Samples then were centrifuged (17,000 x Yellow grease 1.97 3.00 Cottonseed meal 4.99 g for 10 min) and the supernatant fluid stored Cane molasses 2.96 3.50 at -20°C for VFA analysis. Samples were Limestone 1.62 1.67 subjected to all or part of the following Urea .79 1.16 analysis: DM (oven drying at 105°C until no .49 .50 Trace mineral salt" Vitamin A' + + further weight was lost); ash, Kjeldahl N, Monensind + ammonia N (AOAC, 1975); ADF (Goering Chromic oxide .33 and Van Soest, 1970); gross energy (adiabatic Nutrient compositione bomb calorimeter); purines (Zinn and Owens, Net energy, M c m g 1986); VFA concentrations of ruminal fluid Maintenance 2.19 2.27 Cain 1.52 1.58 (gas chromatography using 10% SP-1200/1% Starch, % 55.2 58.4 H 3 P 0 4 on 80/100 Chromosorb W AW packing 13.0 12.5 cp,8 in a 183-cm x 2-mm i.d. glass column with Elher extract, 8 5.5 6.6 column, inlet and detector temperatures mainCa, 8 .80 .mo P, 8 .36 .31 tained at 120, 195 and 200"C,respectively, and with carrier gas [N2] flow rate of 20 ml.min); aDM basis. *race mineral salt contained: CoCO4. .0688;CuSO4, chromic oxide (Hill and Anderson, 1958) and 1.04%; FeSO4. 3.57%; 2110. .75%; MnSO4, 1.071; KI, starch. Starch was assayed as follows: 1) 200 ,0528; and NaCI, 93.4%. mg ground sample was placed in a 2200 Nkg. 20-ml screw-cap culture tube along with 10 ml H 2 0 and gently mixed; 2) the tube was tightly 90mg/kg. %ased on tabular values for individual feed ingredients capped and incubated at 100°C in a water bath (NRC.1984) wirh exception of supplemental fat, which was for 3 h (gelatinization step); 3) the tube was assigned NE,and NEgvalues of 6.03 and 4.79, respectively allowed to cool and 10 ml buffer (9.91 g (Zinn. 1988). sodium acetate [anhydrous] plus 7.27 ml glacial acetic acid in 1 liter HzO), 67 units amyloglucosidase (1 mg enzyme) and 1 drop later. The respective SF corn treatments and toluene were added 4) proceeded as indicated the premix were combined at the time of for amyloglucosidase assay in Trial 2, beginfeeding. Steers were maintained in individual ning at step 3. Microbial organic matter slotted-floor pens (7.6 m2) with ad libitum (MOM) and N (MN) leaving the abomasum access to water. Dry matter intake was were calculated using purines as a microbial restricted to 5.53 kg/d (approximately 85% of marker (Zinn and Owens, 1986). Organic ad libitum) to avoid feed refusals. This intake level was 76% of the average intake observed matter fermented in the rumen (OMF) was for steers in the accompanying growth perfor- considered equal to OM intake minus the mance trial (Trial 2). This difference in feed difference between the amount of total OM intake should be considered when comparing reaching the duodenum and MOM reaching the results for the two trials. Diets were fed in the duodenum. Feed N escape to the small equal portions at 0800 and 2000 daily. intestine was considered equal to total N Following a 2-wk diet adjustment period, leaving the abomasum minus ammonia-N and duodenal and fecal samples were taken from MN and, thus, includes any endogenous all steers twice daily over a period of four contributions. Methane production was calcusuccessive days as follows: d 1, 0750 and lated based on the fermentation balance for 1350; d 2, 0900 and 1500; d 3, 1050 and 1650 observed molar VFA distribution and OM and d 4, 1200 and 1800. Individual samples fermented in the rumen ( W o k 1960) and all consisted of approximately 500 ml duodenal inherent assumptions. The mal was analyzed chyme and 200 g (wet basis) fecal material. as a 3 x 3 latin square design experiment Samples from each steer and within each according to the following model: Yi$ = u +


TABLE 1 . COMPOSlTlON OF BASAL DIETS FED TO STEERSa

DENSITY EFFECTS ON VALUE OF FLAKED CORN

2Sigma awnical CO.,st. Louis, MO. 3StanbioLaboratory Inc. San An~onio,TX. '%yntex Corp., Des Moines, IA.

39°C for 2 h in a shaking water bath; 4) 1 ml of starch hydrolysate solution was transferred to a 10-ml centrifuge tube, 4 ml TCA solution (30 g trichloroacetic acid in 1 liter H20)were added and the tube was vortexed; 5) the tube was incubated at room temperature for 5 min and then centrifuged at 6,000 rpm for 10 min; 6) 4 ml o-toluidine (solution of 6% orthotoluidine in glacial acetic acid)* was transferred into a separate test tube, 400 p1 TCA supernatant solution was added and the tube was covered with a marble and incubated at 100 "C in a water bath for 10 min; 7) the tube was removed and placed in an ice bath for 5 min; and 8) absorbance was read at 630 nm. Porcine pancreatin reactivity to starch was determined as indicated for amyloglucosidase except for the addition of 8 mg porcine pancreatin3 at step 2. The thickness of the SF corn was determined by breaking the flake approximately in half and measuring the thickness in millimeters (using a micrometer) of the flattest spot near the center of the flake. Estimates of thickness represent an average value for 10 whole flakes selected randomly from the air-dry subsamples of each batch (total of five batches per treatment) of processed corn. Composition of the basal diet to which corn was added is shown in Table 1. Diets were prepared at weekly intervals and stored in plywood boxes located in front of each pen. Steers were fed their respective diets once daily at the rate of approximately 110% of appetite. Steers were implanted with Synovex-S4 upon initiation of the trial and again at d 56. Estimates of steer performance were based on pen means. Steers were weighed on two consecutive days at the initiation and completion of the trial. In calculating steer performance, full weights were reduced by 4% to adjust for effects of fill on estimates of live weight gain. Assuming the primary determinant of energy gain was weight gain, energy gain was calculated by the equation: EG = ( . O S 7 W.75)g1.097. where EG is the daily energy deposited (Mcal/d), g is weight gain (kg/d) and W is the mean shrink BW (kg; NRC, 1984). Maintenance energy expended (McaVd, EM) was calculated by the equation: EM = .077W.75(NRC, 1984). From the derived estimated for energy required for maintenance and gain, the net energy for maintenance (NE,,,) and gain (NEg) values of the two diets can be obtained by the process of iteration to fit the relationship: NE, =


Ai + P,+ Tk + E,$, where Yijk is the response variable, Ai is the animal effect, Pj is the period effect, Tk is the treatment effect and Ei$ is the residual error (Hicks, 1973). Treatment effects were tested for linear and quadratic components by means of orthogonal polynomials. Trial 2. Seventy-two crossbred (approximately 25% Brahman blood with the remainder represented by Hereford, Angus, Shorthorn and Charolais breeds in various proportions) steers (312 kg) were blocked by weight and assigned randomly to 18 pens (four steedpen). Pens were equipped with automatic waterers and fence-line feed bunks. Treatments consisted of a finishing diet containing 80% corn that had been flaked to mean densities of .42. .36 and .30 kg/liter. (In avoirdupois units. these are 28, 24 and 20 pounds per bushel.) Steam- flaked corn was prepared as follows: a chest situated directly above the rollers (46 x 61 an comgated) was filled to capacity (441 kg) with corn and brought to a constant temperature at atmospheric pressure of 102'C using steam. The corn was steamed for approximately 20 min before starting the rollers. The first approximately 441 kg of SF corn was allowed to pass from the rollers before material was collected for use in the trial. This preliminary period served for warming the rollers and for adjusting the tension of the rollers to provide a flake with the desired density (.42, .36 or .30kaiter). The retention time of corn in the steam chamber was maintained at 34 min for all three flake density treatments. The SF corn then was allowed to air-dry prior to feeding. In vitro enzymatic digestibility of starch (IVSD) was determined using amyloglucosidase and porcine pancreatin. Samples were prepared by grinding air-dry corn in a Wiley mill to pass through a 2-mm screen. Amyloglucosidase reactivity was determined as follows: 1) 200 mg ground sample were placed in a 20-ml screw-cap culture tube along with 10 ml H20 and 10 ml buffer (9.91 g sodium acetate [anhydrous] plus 7.27 ml glacial acetic acid in 1 liter H20);2) 67 units amyloglucosidase (1 mg enzyme) and 1 drop toluene were added, 3) tubes were tightly capped, gently mixed and incubated at

769

770

ZINN

Flake density, kditer Item

Replicates Dry matter. %*

.42

.36

.30

5

5

5

84

84

85

2.23 mmk In vitro 2-h enzymatic digestibility, % total starch 6.8 AmyloglucosidasebC 14.2 Porcine pancreatinbC FI~ILCthickness.

1.83 9.1 23.0

1.68 12.1 33.0

SD 1

.I3 .9

4.4

‘Mcasurtment taken on corn as it exited the rollers. b ~ a m p ~were e s allowed to air dry prior to analysis. ‘linear effect. P c .01.

377% - .41 (derived from NRC, 1984). Hot carcass weights were obtained from all steers at the time of slaughter. After the carcasses were chilled for 48 h, the following measurements were obtained: 1) longissimus muscle area (ribeye area), taken by direct grid reading of the eye muscle at the 12th rib 2) S.C. fat over the eye muscle at the 12th rib taken at a location 3/4 the lateral length from the chine bone end (adjusted by eye for unusual fat dismbution); 3) kidney, pelvic and heart fat (KPH) as a percentage of carcass weight; 4) marbling score (USDA, 1965) and 5) carcass specific gravity. Carcass composition (percentage water, protein and fat) were based on carcass specific gravity (Garrett and Hinman, 1969). The trial was analyzed as a randomized complete block design experiment with pens as experimental units. The statistical model was as follows: Yij = u + B, + T, + E,., where Yij is the response variable, Bi is the block effect, T, is the treatment effect and Eij is the residual error (Hicks, 1973). Treatment effects were tested for linear and quadratic components by means of orthogonal polynomials. Rerults and Discussion

The grade 2 yellow corn used in this trial had the following composition (DM basis): DM, 88%; ash, 1.74%; ADF, 4.36; N, 1.49% and starch, 71.8%. Moisture uptake by the corn during flaking averaged 4 percentage units (Table 2) and was not affected (P > .lo) by increasing roller tension. This moisture uptake is consistent with the 3 to 5 percentage unit moisture uptakes reported in previous studies (Johnson et al., 1968; Beeson, 1972; Zinn, 1990) involving corn steamed at atmospheric pressure before flaking. Because residence

time of corn in the steam chest was maintained at approximately 34 min for all three corn processing treatments, similar moisture uptakes for the three treatments were expected. However, in many commercial operations where flakers are operated at nearly maximum capacities, changing the roller tension to produce a thinner flake will decrease throughput and, consequently, increase retention time of corn in the steam chest. Whether increased exposure time of corn to steam and heat prior to flaking will influence flake quality differently from what was observed in this study is uncertain. In a previous study (Zinn, 1990), prolonged steaming time (up to 67 min) while holding FD constant (.36 kg/liter) increased both moisture uptake and IVSD. although in vivo site and extent of starch digestion were not affected. Besides moisture uptake, measurements of FD, F T and IVSD are used to set quality standards for SF corn. The choice of standards may reflect the practicality of such measurements. For example, FD measurements must be determined on SF corn obtained immediately beneath the rollers. Thus, whereas FD measures are considered essential for setting appropriate roller tension, they must be obtained at the time the grain is being processed. Flake thickness, on the other hand, may be determined on SF corn at any time following processing (Le., stockpiled corn, laboratory samples of corn or complete mixed diets containing corn). The same largely is true for IVSD estimates. although they are considerably more tedious and costly to measure. The relationships between FD, FT and IVSD are shown in Tables 2 and 3. Flake density was directly related (P < .01) to FT. However, whereas mean values depict a rather close


TABLE 2.RELATIONSHIP BETWEEN DENSITY OF STEAM-FLAKEDCORN AND MEASUREMENTS OF FLAKE THICKNESS AND IN VITRO ENZYMATIC DIGESTIBILITY OF STARCH

77 1


~

Variablesb

X FD,kg/Iiter

Y

Constant

FT,cm

x CoeffiClent

R2

4.576 -.442 -1.561

.7J

.I4 .62 .66

AGR, % starch PPR. 5% starch

,268 ,253 ,796

FD, kg/liler AGR. W starch PPR. 96 starch

,0493 .223 ,747

,162 -.0697 -.268

PPR. % starch

-.OS84

3.45 1

.87

.79

FT.cm

AGR, % starch ~~

37 ~

~~~

*Represents samples of 15 batches of stearn-flakedcorn produced over a period of 3 mo (May through August, 1988) % =I flake density: FT = flake hckness; AGR = amylglucosidse reacuvity; PPR = porcine pancreatin reactivity.

relationship, FD only explained 74% of the variation in F T (Table 3). This comparatively low correlation probably is due, in part, to the intrinsic variation in flake thickness associated with hardness of the kernel and relative tension across the length of the rolls as well as to difficulty of standardizing the FT measurement. Concerning the latter, measurements of flake thickness were taken at the flattest location near the Center of the flake. However, flakes tended to wrinkle. particularly at the lower flake densities, making measurement more difficult and reducing the precision of the FT estimate. Flake density was inversely related (P < .Ol) to IVSD, whether measured using amyloglucosidase or porcine pancreatin. No published studies have examined the influence of FD on IVSD for SF corn, but results are consistent with studies evaluating FD and in vitro digestibility of steam-processed milo and barley (Osman et al., 1970; Trei et al., 1970). Estimates of IVSD obtained using amyloglucosidase were lower than with pancreatin. Nevertheless, the correlation between these two measurements was high (R2 = 3 7 ; Table 3). The FD was more closely associated with estimates of IVSD obtained using amyloglucosidase than those obtained using pancreatin (R2 = .87 vs .79); on that basis, amyloglucosidase may be the preferred of these two enzyme assays. The correlation between IVSD and in vivo starch digestion may be casual rather than causal; only a small fraction of the total starch was fermented in these enzyme assays. The influence of FD of SF corn on characteristics of ruminal and total tract

digestion is shown on Table 4. Consistent with the observed increases in starch digestibility measured in vitro, decreasing the FD resulted in linear increases in postruminal ( P e .05) and total tract (P e .05) digestibility of starch. Ruminal starch digestibility also tended (P > .lo) to increase with decreasing FD. Yet, thinner flaking tended to increase the percentage of total tract digestion that occurred in the rumen. Increased postruminal starch digestibility has been a consistent observation with steam flaking (Theurer, 1986; Zinn, 1987, 1988, 1989). That FD can influence postruminal digestion emphasizes the importance of physical characteristics of feed particles as one principal limitation to small intestinal and, thus, total tract, starch utilization. Ruminal digestion of feed N tended to be lower ( P < .lo) for corn of the intermediate flake density; no reason is apparent. Perhaps processing changed the nature of corn protein or extent of associative effects on ruminal fermentation. Whatever the cause, the response to steam flaking with respect to ruminal degradation of feed N has not been consistent, with some studies (Zinn, 1987, 1988, 1990) showing no difference and others (Prigge et al., 1978; Zinn, 1987) showing increased ruminal escape. Microbial efficiency (MN, g/ kg OM fermented) and protein efficiency (duodenal non-ammonia N/N intake) were similar (P > .lo) across treatments. Apparent digestibility of N in the small intestine and total tract increased linearly (P < .05)with decreasing flake density. Expected postruminal N digestibility (intestinal digest-


TABLE 3. CORRELATIONS AMONG SELECTED MEASURES OF QUALITY OF STEAM-FLAKEDCORNa

772

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Flake density, kg/liter Item

Jntalre. gld OM Starch ADF N GE. Mcdd Leaving abomasum, g/d OM Starch ADF Non-ammonia N Microbial N' Feed Nb Ruminal digestion, 9b intake OM Starch ADF Feed Nb Microbial efficiency' protein efficiencyd Fecal excretion, g/d

SD

.42

.36

.30

5,277 3.089 528 107 24.7

5,191 3.049 529 108 24.5

5,253 3,052 535 109 24.6

2,604 622 360 107 50.3 57.2

2,623 532 437 113 49.4 63.9

2.357 399 354 112 54.9 56.8

60.1 79.8 31.9 46.7 16.0 1.oo

360 185 111 3 .7 2.8

59.0 82.6 17.3 41.1 16.2 1.04

65.6 86.9 34.0 48.1 16.1 1.02

7.1 6.3 21.1 2.8 2.0 .03

OM

920

StarchC ADF

46.0 282 32.3 4.80

868 27.8 292 32.2 4.62

755 10.8 259 27.1 4.09

21 3.7 19 .9 .12

64.0 91.6 19.1 71.2

67.0 95.0 32.0 72.8

67.6 97.2 22.9 76.7

4.7 2.2 19.6

31.9 18.7 14.8 74.4

33.8 16.5 27.5 79.5

30.5 12.8 17.7 81.8

6.8 6.2 17.6 3.3

82.6 98.5 46.7 69.9 3.59

83.3 99.1 44.8 70.3 3.61

85.6 99.6 51.7 75.2 3.71

N' GE, McaVd' Post-ruminal digestion. 46 leaving abomasum OM Starch' ADF

N* Post-ruminal digestion, %I intake OM Starch ADF N

Total uact &gation. 30 OM' Starcha ADF Np DE. Mcal~kfl ~

1.4

.5

.1 3.7 .8 .02

~

'Linear effect, P e .05. b ~ a d r a t i effect. c P < .IO. 'Microbial N. g/kg OM remenled. dthmienal non-ammonia N/N intake. Tinear effect, P e .01. fLmear effect, P < .IO.

ible N, g/d = .68 x ruminal escape feed N + .73 x microbial N - 3; Zinn and Owens, 1981) averaged 95, 93 and 83% of observed for the .42, .36 and .30 kg/liter FD, respectively. Thus, in association with improved postruminal digestibility of starch, posuuminal N digestibility of corn also may be improved as a result of decreasing FD. This explanation is

consistent with results of a previous study (Zinn, 1990) in which small intestinal OM and N digestibilities were 26 and 1 1 % greater, respectively, for SF than for dry-rolled corn diets. Total tract digestibility of OM, N and energy increased linearly ( P < .05) with decreasing FD. Total tract digestibility of ADF


TABLE 4. INFLUENCE OF DENSITY OF STEAM-FLAKED CORN ON CHARACTERISTICS OF DIGESTION OF A FINISHING DIET BY FEEDLOT STEERS (TRIAL1)

773

DENSITY EFFECIS ON VALUE OF FLAKED CORN

Flake density, kg/liter .42

Item Ruminal pHa Ruminal VFA, moVlOO mol Acetateb Propionate' Isobutyrate Butyrate lsovalerate Valerate Methane moductioncd

.36

.30

6.29

6.12

60.0 20.4 1.1 12.5 4.1 1.8 .93

67.0 14.2 1.3 11.2 4.4 1.9 .95

SD

6.08 62.2 19.0

.01

1.5 2.1

1.1

.2

11.9 4.1 1.7 .94

1.3 1.4 .4 .01

'Linear effect. P < .01. bQuadratic effect. P < .05. cQuadratic effect, P < .lo. dMethane. moVmol glucose equivalent fermented.

was not affected (P > .lo) by processing treatment. The increase in starch digestibility from decreasing FD from .42 to .30 kg/liter, although statistically significant (P < .05), was comparatively small (1.1%) in magnitude. Indeed, improvements in total tract digestibility of OM (3.6%), N (7.6%) and energy (3.3%) were more substantial. The influence of FD on ruminal pH, VFA profiles and estimated methane production is shown in Table 5 . Decreasing FD resulted in a linear decrease (P c .01) in ruminal pH. Molar proportions of acetate were higher for the .36

kg/liter FD. The reason for this effect is not clear. In contrast to what might be expected based on changes in in vitro and in vivo digestibility. decreasing FD did not improve either feedlot performance (Table 6) or carcass merit (Table 7). In fact, there was a tendency (P > .lo) for slower weight gain and poorer feed efficiency in steers fed SF corn of the lowest FD. Feed intake was 24% lower for steers in the metabolism trial compared with the growth performance trial. This difference in intake might be expected to accentuate differences in

TABLE 6. INFLUENCEOF DENSITY OF STEAM-FLAKEDCORN ON FEEDLOT PERFORMANCE AND ESTIMATED NET ENERGY VALUE OF DIETS FED TO STEERS (TRIAL 2)

Item Live wt, kg' lnitial Fmal Live wt gain, kg/d DM intake, kg/d DM conversion Diet net energy, Mcaykg Maintenaoce

Gain Observed/expected diet net energyb Maintenance

Gain

Flake density, kg/liter .36 .30

.42 308 465 1.40 7.49 5.37

313 470 1.39 7.31

SD

5.24

315 462 1.32 7.16 5.48

13 23 .13 .5 1 .28

2.25 1.56

2.31 1.62

2.27 1.58

.06 .06

.99 .98

1.02 1.02

1.oo

.03

.99

.04

'lnitial and fmal weights reduced 4% to account for fill. bExpecvd diet net energy values were calculated on the basis of diet formulation and tabular values for individual feed ingredients (NRC,1984) with excxption of supplemental fat. which was assigned NE, and NEg values of 6.03 and 4.79,

rcspcctively (Zm,1988).


TABLE 5. INFLUENCE OF DENSITY OF STEAM-FLAKEDCORN ON RUMINAL pH, VFA PROFILES AND METHANE PRODUCTION 4 HOURS POSTPRANDIAL (TRIAL 1)

174

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Item

.42

Carcass wt. kg Dressing percentage Rib eye area, cm2 Fat thickness, cm KPH, ba Marbling score, depesb Retail yield, 96 Carcass specific gravity Carcass composition, % Water Protein Fat

305 65.6 88.1

Flake density, kglliter .30 .36

1.04

2.33 3 .!B 51.8 1.053 51.3 15.2 29.3

SD

307 65.5 84.9 .97 2.42 3.82 51.5 1.053

300 64.8 83.5 .97 2.38 3.% 51.5 1.055

17 1.01 4.9 .I6

51.2

51.9 15.4 28.4

1.3 .4 1.8

15.2 29.5

.I8

.35 .6

,003

'Kidney, pelvic and hean fat as a percentage of carcass weight. b i d :~ i n i m u mslight = 3.minimum mall = 4, etc.

diet digestibility as a result of processing. However, the increase in feed intake also might have further exacerbated the effects of FD on ruminal pH (Table 5 ) which, in turn, might have caused digestive dysfunction and reduced performance of some individual animals. This assumption is consistent with the greater variability in treatment responses that were observed for steers in the .30 kg/liter FD treatment group. For example, the group variance (s2) for weight gain response in steers fed the .30 kg/liter FD corn- based diet was 366% greater than the average for the other two treatment groups fed the higher-FD corn. More work is needed to evaluate the influence of level of feed intake, forage level and the potential for buffers in diets containing highly processed feed grains. Matsushima and Montgomery (1967) compared steamed corn flaked to .79 vs 2.21 mm thickness in a 163-d growth performance trial involving 27 individually fed heifers. They observed (statistical analysis of the data was not presented) a 4.4% increase in live weight gain and a 7.8% improvement in feed conversion for heifers fed a finishing diet containing the thinner flaked corn. The thicker flake corresponds closely to the higher FD treatment in the present mal, whereas, the thinner flake was only half as thick (47%). Based on the regression equation shown in Table 3, the FT reported for their mal would correspond to FD of .18 and .41 kg/liter for the .79 and 2.21 cm flake treatments, respectively. In contrast to observations of Matsushima and Montgomery (1%7), there was a tendency

(P > .lo) toward poorer weight gain and DM conversion for steers consuming the diet containing SF corn of the lowest density (.30 kgiter, Table 6). However, this appeared to reflect reduced feed intake rather than decreased utilization of the corn. The net energy value of the diets as determined from feedlot performance was very similar to what was expected based on diet composition alone (observed/expected = 1.003, Table 6). Implications

Decreasing the density of SF corn from .42 to .30 kg/liter increases susceptibility of corn starch to in vitro and in vivo digestion and may improve N utilization. However, decreasing FD also may lower ruminal pH, so consequently feedlot performance may not be enhanced. An ideal processing procedure for corn may be one that decreases rate of ruminal fermentation while increasing total tract digestibility. Literature Cited

AOAC. 1975. Official Methods of Analysis (12th Ed.). Association of Official Analytical Chemists. Washington, DC. Beeson. W. M. 1972. Effect of steam-flaking, roasting. popping and extrusion of grains on their nutritional value for beef cattle. In: Effect of Processing on the Nutritive Value of Feeds. p 326.National Academy of Sciences, Washington, DC. Garrett. W. N. 1%5. Comparative feeding value of steamrolled or ground barley and milo for feedlot cattle. J. Anim. Sci. 24:726. Garrett, W. N. and N. Hinman. 1969. Re-evaluation of the


TABLE 7. INFLUENCEOF DENSITY OF STEAM-FLAKED CORN ON CARCASS MERlT AND EMPTY BODY COMPOSITION OF FEEDLOT STEERS (TRIAL 2)


York. Hill, F. N. and D. L. Anderson. 1958. Comparison of awtabolizable energy and productive energy determinations with growing chicks. J. Nun. 64:587. Johnson, D. E., J. K. Matsushiia and K. L Knox. 1%8. Utilization of flaked vs. cracked corn by steers with obstrvation on starch modification. J. Anim. Sci. 27: 1431. Matsushima, J. K.and R. L. Montgomery. 1967. Tbe thick and thin of flaked corn.Colorado Farm Home Res. 17: 4.

NRC,1984. Nutrient Rquirunent of Beef Cattle (61h Rev. Ed.). National Academy Press, Washington. DC. Osman. H. F.. B. Theurer, W. H. Hale and S. M. Mehen. 1970. Influence of grain processing on in vitro enzymatic starch digestion of barley and sorghum grain. J. Nuu. 100:1133. P m a , J. C.. S. Mehen, W. H. Hale, M. Little and B. Theurcr. 1969. Digestibility of dry rolled and steam

processed flaked barley. J. Anim. Sci. 28:425. Rigge, E. C., M. L. Galyean, F. N. Owens, D. G. Wagner and R. R. Johnson. 1978. Microbial protein synthesis in steers fed processed and corn rations. J. Anim. Sci. 46: 249. Theurer, C. 8. 1986. Grain processing effects on starch utilization by ruminants. J. Anim. Sci. 63:1649. Trei, J.. W.H. Hale and B. Theurer. 1970. Effects of grain processingon in vitro gas production. J. Anim. Sci. 30: 825. USDA. 1%5. Official United States Standards for Grades of Carcass Beef. USDA, C&MS, SRA 99. Wolin. M. J. 1960. A theoretical lumen fermentation balance. J. Dairy Sci. 43:1452. Zmn. R. A. 1987. Influence of lasalocid and monensin plus tylosin on comparative feeding value of steam-flaked versus dry-rolled corn diets for reedlot cattle. J. Anim. Sci. 65256. Zinn. R. A. 1988.Influence of temperingon the comparative fezding value of rolled and steam-flaked corn for feedlot steers. Roc. Western S e c . Am SOC.h i m . Sci.39:386. Zinn. R. A. 1990. Influence of steaming time on site of digestion of flaked corn in steers. J. Anim. Sci. 68:776. Zinn. R. A. and F. N. Owens. 1981. Predicting net uptake of nonammonia N from the small intestine. In: F. N . Owens (Ed.) Requirements of Cattle Symposium. Oklahoma Agnc. Exp. Sta. MP-109:133. Zinn. R. A. and F. N. Owens. 1986. A rapid procedure for purine measurement and its use for estimating net ruminal protein synthesis. Can. J. Anim. Sci. 66157.


relationship between carcass density and body composition of beef steers. J. h m . Sci. 28:l. Gocring, H. K. and P. I. Van Soest. 1970. Forage fiber analysts (apparatus,reagents, procedures, and some applications). Agric. Handbook 379. ARS, ASDA. Washington, DC. Hale. W. H.. L. Cuitun. W. J. Saba. B. Taylor and B. Theurer. 1966. Effect of steam processing and flaking milo and barley on performance and digestion by steers. I. Anim. Sci. 25392. Hicks, C. R. 1973. Fundamental Concepts in the Design of Experiments. Holt, Rinehart and Winston. Inc.. New

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The modern feedlot for finishing cattle.

Influence of dry-rolled corn processing and increasing dried corn distillers grains plus solubles inclusion for finishing cattle on growth performance and feeding behavior.

Effects of feeding growing cattle high-concentrate diets at a restricted intake on feedlot performance.

The nasopharyngeal microbiota of feedlot cattle.

Influence of Feeding Enzymatically Hydrolyzed Yeast Cell Wall on Growth Performance and Digestive Function of Feedlot Cattle during Periods of Elevated Ambient Temperature.

Treatment of feedlot cattle in Alberta for gastrointestinal nematodes.

Methodological comparisons for antimicrobial resistance surveillance in feedlot cattle.

Are super-shedder feedlot cattle really super?

Acidosis in feedlot cattle: practical observations.

The influence of choice feeding and cereal type (corn or triticale) during the finishing period on performance of mule ducks.

Dynamics of ruminal ciliated protozoa in feedlot cattle.

Feeding value and nutrient preservation of high moisture corn ensiled in conventional silos forlactating dairy cows.

Nutritional and dietary interrelationships with diseases of feedlot cattle.

Comparative feeding performance and digestive physiology of Helicoverpa armigera (Lepidoptera: Noctuidae) larvae-fed 11 corn hybrids.

Evaluating the cost implications of a radio frequency identification feeding system for early detection of bovine respiratory disease in feedlot cattle.

Effect of variety and drying method on the nutritive value of corn for growing pigs.

Effect of haylage and monensin supplementation on ruminal bacterial communities of feedlot cattle.

Effect of distillers feedstuffs and lasalocid on Campylobacter carriage in feedlot cattle.

Effects of three dehorning techniques on behavior and wound healing in feedlot cattle.

The effect of feeding high fat diet to beef cattle on manure composition and gaseous emission from a feedlot pen surface.

Influence of feeding coarse corn on performance, nutrient utilization, digestive tract measurements, carcass characteristics, and cecal microflora counts of broilers.

Cattle feeding deterrents emitted from cattle feces.

Effects of purified lignin on in vitro rumen metabolism and growth performance of feedlot cattle.

Methaphylactic effect of tulathromycin treatment on rumen fluid parameters in feedlot beef cattle.