NUTRITION, FEEDING, AND CALVES Effect of Fat from Whole Soybeans on Performance of Dairy Cows Fed Rations Differing In Fiber Level and Particle Size1 R. J. GRANT2 and S. J. WEIDNER Department of Animal Sciences University of Nebraska Lincoln 68583-0908 ABSTRACT
higher dietary NDF and larger particle size promoted greater intake with no effect on FCM yield. (Key words: supplemental fat, soybeans, fiber, particle size)
Two trials were conducted with lactating dairy cows to detennine effects on intake. perfonnance, and chewing activity of supplemental fat in early lactation diets that differed in fiber level and particle size. In trial I, whole raw soybeans were added at 11.6% of ration DM to alfalfa silage-based TMR containing either finely chopped silage or the same silage with 8.1 % coarsely chopped alfalfa hay. Each combination of soybeans (0 or 11.6%) and silage (fine or hay added) was fed as an isocaloric, isonitrogenous TMR to eight Holstein cows in early lactation in a replicated Latin square design with 4-wk periods. Addition of soybeans decreased DMI for fine silage. With silage plus hay, soybean addition decreased milk yield and protein content but increased fat test so that FCM was unchanged. Silage plus hay promoted chewing activity with no interaction of forage particle size with fat addition on chewing activity. In trial 2, TMR based on alfalfa and com silage contained either 25 or 29% NDF and 0 or 11.6% soybeans. Otherwise, trials 1 and 2 were similar. Soybean addition decreased DMI with low NDF diets. Addition of fat from soybeans had no effect on milk yield or composition, but low fiber decreased fat test and chewing activity. When .4 to .5 kgld of supplemental fat from whole raw soybeans was fed,
Abbreviation key: AS =alfalfa silage, no hay, ASH = alfalfa silage plus coarsely chopped alfalfa hay, EE = ether extract, HF = high fiber, 29% NDF ration, LF = low fiber, 25% NDF ration, NFC = nonfiber carbohydrates, WRS = whole raw soybeans. INTRODUCTION
Received January 10. 1992. Accepted May 26. 1992. 1Published with the approval of the director as Paper Number 96%. Journal Series. Nebraska Agricultural Research Division. 2Reprint requests. 1992 J Dairy Sci 75:2742-2751
Maximum energy intake during early lactation allows cows to attain optimal production of SCM. Feeding strategies that increase energy density of the ration include higher percentage of nonfiber carbohydrates (NFC) and use of supplemental fat. Feeding of excessive NFC predisposes cows to rumen acidosis and milk fat depression (13). Although the proper time to begin fat supplementation has not been established (24), supplemental fat may effectively increase the energy density of diets for early lactation cows and avoid metabolic problems associated with high NFC intakes. By partially replacing dietary NFC, supplemental fat permits lower NFC intake and potentially higher intakes of fiber. The effect of supplemental fat on lactational perfonnance may be evaluated by substituting fat for concentrates in a manner that increases the NEL content of the test ration compared with that of a control ration or with that of isocaloric rations. Most research has examined the effect of added fat from oilseeds (15), tallow (10), or rumen-inert sources (5) on milk yield using diets the were not isocaloric. Use of isocaloric diets (9) tests the suitability of energy sources, separately from dietary energy, for optimal SCM yield during early lactation.
2742
DIETARY FAT AND FIBER
Few data are available to evaluate supplemental fat in isocaloric rations. Oilseeds, such as whole raw soybeans (WRS), are becoming a commonly used source of supplemental fat, containing an average of 18 to 20% ether extract (EE) in DM (18). Recent research with high fiber diets (37% NDF) showed no benefit of roasted over WRS (4). Inclusion of the cheaper WRS at 9.4% of ration DM improved total tract DM and CP apparent digestibilities but did not alter milk yield or composition. In contrast, other research has shown lower nutrient digestibilities for WRS fed at 11 % of ration DM than for diets containing soybean meal (16). One key nutritional factor in determining the performance response to any supplemental fat source is ration fiber content (5). To feed fat successfully, it generally is recommended that dairy cows consume adequate effective fiber, but what constitutes adequate intake of effective fiber has not been determined. Fiber promotes chewing activity and salivation (12) and minimizes the potential for negative effects of fat on rumen microbes (14). Researchers have examined the effect of supplemental animal-vegetable fat in high forage diets at one fiber level (19). Optimal effective fiber content of rations containing supplemental fat needs to be determined. Canale et al. (5) found no significant interaction between supplemental Ca salts of fatty acids (0 vs..5 kg/d per cow) and ration NDF (25 vs. 31%); however, Ca salts of fatty acids are inert in the rumen. The interaction of a potentially rumen-available fat source, such as WRS, with both aspects of effective fiber (level and particle size) has not been examined. A 9 to 11 % addition of WRS to high fiber diets affected nutrient digestion (4, 16). Therefore, 11% added WRS was chosen in this study. Our objectives were to measure the effect of rumen-available fat from WRS in isocaloric rations on fiber intake and performance, chewing activity, and plasma glucose concentrations of early lactation dairy cows fed diets differing in fiber percentage and particle size. MATERIALS AND METHODS
Trial 1
Cows and Treatments. Eight Holstein cows (four primiparous) in early lactation were used
2743
in a replicated 4 x 4 Latin square design. Cows averaged 16 DIM (± 6 d) when they were assigned to treatment. Dietary treatments were 1) alfalfa silage (AS) finely chopped to a .64cm theoretical length with 11.6% (dry basis) added WRS (AS + WRS); 2) the same silage without WRS (AS - WRS); 3) the same silage with 8.1 % (dry basis) coarsely chopped alfalfa hay (ASH) of similar quality to increase particle size and 11.6% added WRS (ASH + WRS); and 4) the same mixture of silage and hay without WRS (ASH - WRS). All diets were fed as TMR and were formulated to be essentially isocaloric and isonitrogenous (18.5% CP). Diets contained 52.2 to 52.8% forage, 34.0 to 36.3% shelled com, and either 8.8% soybean meal or 11.6% WRS. Ether extract ranged from 3.8% for the unsupplemented diets to 6.0% for those containing WRS (Table 1). Experimental periods were 28 d; the last 7 d were used for sample and data collection. This protocol has been used successfully to measure dairy cow performance responses to diets differing in NDF and fat addition (3, 5). Diets were formulated to meet or to exceed slightly the NRC (18) requirements for cows weighing 580 kg and yielding 32 kg/d of milk. Diets were fed once daily in amounts to ensure 10% orts. Amounts offered and refused were recorded daily. Body weight was measured weekly immediately after milking. Sample Collection and Analysis. Samples of forages and TMR were composited weekly for analyses. Composited samples were oven-dried (60°C), ground through a Wiley mill (1-mm screen; Arthur H. Thomas Co., Philadelphia, PA), and analyzed for CP (2), amylasemodified NDF (22), ADF (11), and EE (2). A vertically oscillating sieve shaker (W. S. Tyler, Inc., Mentor, OH) was used to determine particle distributions of dried forage and experimental TMR samples that were collected weekly. Arithmetic (12) and geometric mean particle sizes (27) of samples were calculated. Daily milk yields were recorded electronically. Composite p.m. and a.m. milk samples were collected twice during the last week of each period and analyzed for fat and protein percentages (Milko-Scan Fossamatic, Foss Food Technology Corp., Eden Prairie, MN). Calculation of milk composition was weighted according to a.m. and p.m. milk yield. Journal of Dairy Science Vol. 75, No. 10. 1992
2744
GRANT AND WEIDNER
TABLE 1. Composition of rations differing in forage particle size and soybean addition for trial 1. Dietl Item
AS + WRS
AS - WRS
OM, %
57.5
58.1
CP AOF NDF
18.5 19.4 29.5 6.0 1.73
18.9 19.7 29.6 3.8 1.71
52.2
52.8
34.0
36.3 8.8
EE2
NEL,3 McalIkg
ASH + WRS 59.9 (% of OM) 18.4 19.5 29.3 6.0 1.73
ASH - WRS 59.3 18.7 19.8 29.4 3.7 1.71
(% composition, OM basis) Alfalfa silage Alfalfa hay Shelled corn Soybean meal, 44% CP Whole raw soybeans Vitamin-mineral supplement4
11.6 2.2
2.1
44.1 8.1 34.0 11.6 2.2
44.6 8.2 36.3 8.8 2.1
lAS = Alfalfa silage (finely chopped), ASH = alfalfa silage plus coarsely chopped alfalfa hay, WRS = whole raw soybeans. 2EE = Ether extract. 3Calculated from NRC (18). 4Vitamins and minerals were formulated to meet or to exceed requirements according to NRC (18).
Blood samples for glucose analyses were drawn from the coccygeal vein at 0, 1, 3, and 6 h after the a.m. feeding. Blood was collected into 5-ml tubes containing potassium oxalate as an anticoagulant and sodium fluoride as a glycolytic inhibitor. Samples were centrifuged at 2000 X g for 25 min, and plasma glucose was measured using a Technicon Autoanalyzer System (Technicon Instruments, Inc., Tarrytown, NY). Total chewing, eating, and ruminating times were recorded during wk 4 of each period. The chewing action of individual cows was observed and recorded every 5 min during 24 h. Rate of rumination (chews per bolus) was determined by observing individual cows during bouts of rumination. Although not an absolute measurement, this method of scan sampling yields reliable estimates given the short interval between observations (28). Rumination activity (minutes per kilogram of DM and fiber intake) was determined. Data were analyzed as a replicated 4 x 4 Latin square (1) using the general linear models procedure of SAS (23) with a factorial arrangement of treatments. Orthogonal comparisons were 1) fine silage versus fine silage Journal of Oairy Science Vol. 75, No. 10, 1992
plus chopped hay, 2) WRS fed at 0 or 11.6% of dietary DM, and 3) interaction between physical form of silage and addition of WRS. Unless otherwise stated, statistical significance was determined at P < .10. Trial 2
Cows and Treatments. Eight early lactation Holstein cows (four primiparous) were used in a replicated 4 x 4 Latin square design. Cows averaged 17 DIM (± 7 d) when they were randomly assigned to dietary treatments. Dietary treatments were 1) low fiber (LF), 25% NDF with 11.6% WRS (LF + WRS); 2) 25% NDF without WRS (LF - WRS); 3) high fiber (HF), 29% NDF with 11.6% WRS (HF + WRS); and 4) 29% NDF without WRS (HFWRS). All diets were fed as TMR and were formulated to be nearly isocaloric within a fiber percentage and isonitrogenous (18.0% CP). As formulated, diets HF + WRS and HF - WRS had .03 and .05 Mcal of NEdkg less than diets LF + WRS and LF - WRS. On a DM basis, diets LF + WRS and LF - WRS contained 39% forage (AS and com silage), and diets HF + WRS and HF - WRS contained about 49% (Table 2). All other aspects of
2745
DIETARY FAT AND FIBER TABLE 2. Composition of rations differing in fitw percentage and soybean addition for trial 2. Dietl Item
LF + WRS
LF - WRS
DM,%
67.9
68.9
65.3 (% of DM)
64.0
CP ADF NDF EE2 NEL,3 Mca1lkg
17.5 14.2 25.0 5.7 1.78
17.8 14.4 25.5 3.5 1.77
17.8 17.1 28.8 5.7 1.75 (% composition, DM basis)
17.9 17.4 29.1 3.4 1.73
Alfalfa silage Corn silage Shelled corn Soybean meal, 44% CP Whole raw soybeans Vitamin-mineral supplement4
19.5 19.5 40.0 6.8 11.7 2.5
19.7 19.7 42.4 15.7 2.5
HF + WRS
24.3 24.3 30.9 6.6 11.6 2.3
HF - WRS
24.8 24.8 33.4 14.7 2.3
lLF = Low fiber, 25% NDF ration; HF = high fiber, 29% NDF ration, WRS = whole raw soybeans. 2EE = Ether extract. 3Calculated form NRC (18). 4Vitamins and minerals were formulated to meet or to exceed requirements according to NRC (18).
design, sample collection, analyses, and statistical treatment of results were identical to those of trial 1. RESULTS AND DISCUSSION
Addition of WRS to a diet changes not only the fat but also the proportion of escape protein (18). In an effort to avoid protein effects on cow performance among diets, diets were formulated to contain 18.5% CP with 33 to 34% of CP as undegraded intake protein using estimates of protein degradability given by NRC (18). Replacement of a portion of the corn and soybean meal with WRS allowed all diets to remain nearly isocaloric in trial 1. Because diets essentially were isocaloric in trial 1, performance responses were interpreted as being due to fiber particle size or to WRS addition. In trial 2, addition of 11.6% WRS increased EE from 3.5 to 5.7%. Diets were formulated to contain 18% CP with 35 to 38% undegraded intake protein in an effort to minimize effects of source of soybean CP on cow performance. Because diets essentially were isocaloric at an NDF percentage, as in trial 1, cow responses in trial 2 were interpreted as being due to NDF (or energy) percentage or WRS addition.
Addition of ASH increased the mean particle size of diets ASH + WRS and ASH - WRS in trial 1 (Table 3). In trial 2, particle size actually was smaller for the higher NDF than for the lower NDF diets. Both simple arithmetic and geometric mean particle sizes were calculated. Calculation of an arithmetic mean particle size requires no assumptions concerning the sample particle distribution, but determination of a geometric mean particle size assumes thai the distribution of feed particles is log normal (27). Although the validity of this assumption may be questioned when particle size of coarsely chopped forages is measured (12), calculation of geometric mean particle size allows more extensive comparison with reported literature (27). Geometric mean particle sizes consistently were smaller than the arithmetic mean particle sizes for all forages and diets (Table 3). Furthermore, addition of WRS increased the mean particle size of TMR because of entrapment of WRS on the larger screen sizes (~3.35 mm). This interaction of whole grains and measurement of dietary particle size has been discussed (12). Particle distribution of forages is depicted in Figure 1 to complete the description of dietary particle size. Chopped alfalfa hay contained 81 % of particles >1.18-rom screen size Journal of Dairy Science Vol. 75, No. 10, 1992
2746
GRANT AND WEIDNER
TABLE 3. Particle sizes of forages and rations fed during trials 1 and 2.
Sample!
Arithmetic mean particle size
Geometric mean particle size 2
Logarithmic SD
(mm)
Recovery3 (%)
Trial I AS Alfalfa hay AS + WRS AS - WRS ASH + WRS ASH - WRS
3.01 3.30 3.48 3.01 3.56 3.34
1.89 2.19 2.81 2.50 2.84 2.60
Trial 2 AS Com silage LF + WRS LF - WRS HF + WRS HF - WRS
3.01 4.97 4.14 3.45 4.07 3.56
1.89 4.28 3.05 2.43 2.91 2.27
.14 .18
.11 .19 .16 .10 .14
.11 .15 .17 .16 .17
99.0 99.1 99.0 99.8 99.9 99.7 99.0 98.9 99.6 99.1 99.8 99.7
1AS = Alfalfa silage (finely chopped); ASH = alfalfa silage plus coarsely chopped alfalfa hay; WRS = whole raw soybeans; LF = low fiber, 25% NDF ration; HF = high fiber, 29% NDF ration.
2Calculated according to Waldo et al. (27). 3Recovery of original sample on sieves when weighed.
and com silage nearly 83% compared with AS, which contained only 47% of particles >1.18mm screen size (Figure 1). Particles retained on the ~ 1. 18-mm screen required rumination and particle size reduction for passage from the reticulorumen in sheep (21). The critical size for escape in dairy cattle is likely closer to the 2.36-mm screen size (12). In trial 1, diet ASH - WRS contained 32% more particles >2.36mm screen size than did diet AS - WRS. Therefore, considerably more potential existed for rumination on the coarse forage diets (ASH + WRS and ASH - WRS) than on the finer forage diets (AS + WRS and AS - WRS) in trial 1. In trial 2, dietary particles retained on the ~2.36-mm screen were similar for all diets (54% for LF, HF - WRS; 65% for LF, HF + WRS). Therefore, altered rumination activity should have been due to NDF percentage or WRS addition and not due to differences in forage particle size for trial 2.
7.1% and reduced forage and ADF intakes as percentages of BW by 10.5 and 10.0%, respectively, for AS diets. As expected, EE intake increased from .76 to 1.10 kgld with WRS addition. Similar to other research with lactating dairy cows fed alfalfa-based rations (12), no effects of forage particle size on DMI or
OMI and Fiber Intake
Figure 1. Particle distributions of alfalfa silage, chopped alfalfa hay. and com silage used in trials 1 and 2 as determined by dry sieving. Chopped alfalfa hay contained 81 % of particles > U8-mm screen size, com silage had 83% >U8-mm screen size, and alfalfa silage had 47% >1.18-mm screen size.
Table 4 presents DMI and fiber intake for trials 1 and 2. In trial 1, addition of 11.6% WRS decreased daily DMI by approximately Journal of Dairy Science Vol. 75. No. 10, 1992
30
•
1
Com silage
m
Alfalfa silage
[J Chopped ""alia hay
6.30 >9.50
DIETARY FAT AND FIBER
2747
TABLE 4. Intake of DM components as influenced by fiber percentage, particle size, and supplemental fat from whole raw soybeans.\
Component Total DMI kg/d··c.d.• % of BW·.b,c.d,e Forage DMI kg/d·.c,d.• % of BW··b.c.d,e ADF Intake kg/da,c.d.• % of BW··b,c.d.• NDF Intake kg/da,c.d.• % of BW··c.d,e EE3 Intake kg/da,d % of BW··d
Trial ]2 AS AS ASH ASH + WRS - WRS + WRS - WRS
Trial 2 LF
SE
LF
HF
HF
+ WRS - WRS + WRS - WRS
SE
18.4 3.3
20.0 3.6
18.4 3.3
19.6 3.4
.8 .1
22.2 3.7
25.4 4.2
22.0 3.7
23.0 3.9
.6
higher dietary NDF and larger particle size promoted greater intake with no effect on FCM yield. (Key words: supplemental fat, soybeans, fiber, particle size)
Two trials were conducted with lactating dairy cows to detennine effects on intake. perfonnance, and chewing activity of supplemental fat in early lactation diets that differed in fiber level and particle size. In trial I, whole raw soybeans were added at 11.6% of ration DM to alfalfa silage-based TMR containing either finely chopped silage or the same silage with 8.1 % coarsely chopped alfalfa hay. Each combination of soybeans (0 or 11.6%) and silage (fine or hay added) was fed as an isocaloric, isonitrogenous TMR to eight Holstein cows in early lactation in a replicated Latin square design with 4-wk periods. Addition of soybeans decreased DMI for fine silage. With silage plus hay, soybean addition decreased milk yield and protein content but increased fat test so that FCM was unchanged. Silage plus hay promoted chewing activity with no interaction of forage particle size with fat addition on chewing activity. In trial 2, TMR based on alfalfa and com silage contained either 25 or 29% NDF and 0 or 11.6% soybeans. Otherwise, trials 1 and 2 were similar. Soybean addition decreased DMI with low NDF diets. Addition of fat from soybeans had no effect on milk yield or composition, but low fiber decreased fat test and chewing activity. When .4 to .5 kgld of supplemental fat from whole raw soybeans was fed,
Abbreviation key: AS =alfalfa silage, no hay, ASH = alfalfa silage plus coarsely chopped alfalfa hay, EE = ether extract, HF = high fiber, 29% NDF ration, LF = low fiber, 25% NDF ration, NFC = nonfiber carbohydrates, WRS = whole raw soybeans. INTRODUCTION
Received January 10. 1992. Accepted May 26. 1992. 1Published with the approval of the director as Paper Number 96%. Journal Series. Nebraska Agricultural Research Division. 2Reprint requests. 1992 J Dairy Sci 75:2742-2751
Maximum energy intake during early lactation allows cows to attain optimal production of SCM. Feeding strategies that increase energy density of the ration include higher percentage of nonfiber carbohydrates (NFC) and use of supplemental fat. Feeding of excessive NFC predisposes cows to rumen acidosis and milk fat depression (13). Although the proper time to begin fat supplementation has not been established (24), supplemental fat may effectively increase the energy density of diets for early lactation cows and avoid metabolic problems associated with high NFC intakes. By partially replacing dietary NFC, supplemental fat permits lower NFC intake and potentially higher intakes of fiber. The effect of supplemental fat on lactational perfonnance may be evaluated by substituting fat for concentrates in a manner that increases the NEL content of the test ration compared with that of a control ration or with that of isocaloric rations. Most research has examined the effect of added fat from oilseeds (15), tallow (10), or rumen-inert sources (5) on milk yield using diets the were not isocaloric. Use of isocaloric diets (9) tests the suitability of energy sources, separately from dietary energy, for optimal SCM yield during early lactation.
2742
DIETARY FAT AND FIBER
Few data are available to evaluate supplemental fat in isocaloric rations. Oilseeds, such as whole raw soybeans (WRS), are becoming a commonly used source of supplemental fat, containing an average of 18 to 20% ether extract (EE) in DM (18). Recent research with high fiber diets (37% NDF) showed no benefit of roasted over WRS (4). Inclusion of the cheaper WRS at 9.4% of ration DM improved total tract DM and CP apparent digestibilities but did not alter milk yield or composition. In contrast, other research has shown lower nutrient digestibilities for WRS fed at 11 % of ration DM than for diets containing soybean meal (16). One key nutritional factor in determining the performance response to any supplemental fat source is ration fiber content (5). To feed fat successfully, it generally is recommended that dairy cows consume adequate effective fiber, but what constitutes adequate intake of effective fiber has not been determined. Fiber promotes chewing activity and salivation (12) and minimizes the potential for negative effects of fat on rumen microbes (14). Researchers have examined the effect of supplemental animal-vegetable fat in high forage diets at one fiber level (19). Optimal effective fiber content of rations containing supplemental fat needs to be determined. Canale et al. (5) found no significant interaction between supplemental Ca salts of fatty acids (0 vs..5 kg/d per cow) and ration NDF (25 vs. 31%); however, Ca salts of fatty acids are inert in the rumen. The interaction of a potentially rumen-available fat source, such as WRS, with both aspects of effective fiber (level and particle size) has not been examined. A 9 to 11 % addition of WRS to high fiber diets affected nutrient digestion (4, 16). Therefore, 11% added WRS was chosen in this study. Our objectives were to measure the effect of rumen-available fat from WRS in isocaloric rations on fiber intake and performance, chewing activity, and plasma glucose concentrations of early lactation dairy cows fed diets differing in fiber percentage and particle size. MATERIALS AND METHODS
Trial 1
Cows and Treatments. Eight Holstein cows (four primiparous) in early lactation were used
2743
in a replicated 4 x 4 Latin square design. Cows averaged 16 DIM (± 6 d) when they were assigned to treatment. Dietary treatments were 1) alfalfa silage (AS) finely chopped to a .64cm theoretical length with 11.6% (dry basis) added WRS (AS + WRS); 2) the same silage without WRS (AS - WRS); 3) the same silage with 8.1 % (dry basis) coarsely chopped alfalfa hay (ASH) of similar quality to increase particle size and 11.6% added WRS (ASH + WRS); and 4) the same mixture of silage and hay without WRS (ASH - WRS). All diets were fed as TMR and were formulated to be essentially isocaloric and isonitrogenous (18.5% CP). Diets contained 52.2 to 52.8% forage, 34.0 to 36.3% shelled com, and either 8.8% soybean meal or 11.6% WRS. Ether extract ranged from 3.8% for the unsupplemented diets to 6.0% for those containing WRS (Table 1). Experimental periods were 28 d; the last 7 d were used for sample and data collection. This protocol has been used successfully to measure dairy cow performance responses to diets differing in NDF and fat addition (3, 5). Diets were formulated to meet or to exceed slightly the NRC (18) requirements for cows weighing 580 kg and yielding 32 kg/d of milk. Diets were fed once daily in amounts to ensure 10% orts. Amounts offered and refused were recorded daily. Body weight was measured weekly immediately after milking. Sample Collection and Analysis. Samples of forages and TMR were composited weekly for analyses. Composited samples were oven-dried (60°C), ground through a Wiley mill (1-mm screen; Arthur H. Thomas Co., Philadelphia, PA), and analyzed for CP (2), amylasemodified NDF (22), ADF (11), and EE (2). A vertically oscillating sieve shaker (W. S. Tyler, Inc., Mentor, OH) was used to determine particle distributions of dried forage and experimental TMR samples that were collected weekly. Arithmetic (12) and geometric mean particle sizes (27) of samples were calculated. Daily milk yields were recorded electronically. Composite p.m. and a.m. milk samples were collected twice during the last week of each period and analyzed for fat and protein percentages (Milko-Scan Fossamatic, Foss Food Technology Corp., Eden Prairie, MN). Calculation of milk composition was weighted according to a.m. and p.m. milk yield. Journal of Dairy Science Vol. 75, No. 10. 1992
2744
GRANT AND WEIDNER
TABLE 1. Composition of rations differing in forage particle size and soybean addition for trial 1. Dietl Item
AS + WRS
AS - WRS
OM, %
57.5
58.1
CP AOF NDF
18.5 19.4 29.5 6.0 1.73
18.9 19.7 29.6 3.8 1.71
52.2
52.8
34.0
36.3 8.8
EE2
NEL,3 McalIkg
ASH + WRS 59.9 (% of OM) 18.4 19.5 29.3 6.0 1.73
ASH - WRS 59.3 18.7 19.8 29.4 3.7 1.71
(% composition, OM basis) Alfalfa silage Alfalfa hay Shelled corn Soybean meal, 44% CP Whole raw soybeans Vitamin-mineral supplement4
11.6 2.2
2.1
44.1 8.1 34.0 11.6 2.2
44.6 8.2 36.3 8.8 2.1
lAS = Alfalfa silage (finely chopped), ASH = alfalfa silage plus coarsely chopped alfalfa hay, WRS = whole raw soybeans. 2EE = Ether extract. 3Calculated from NRC (18). 4Vitamins and minerals were formulated to meet or to exceed requirements according to NRC (18).
Blood samples for glucose analyses were drawn from the coccygeal vein at 0, 1, 3, and 6 h after the a.m. feeding. Blood was collected into 5-ml tubes containing potassium oxalate as an anticoagulant and sodium fluoride as a glycolytic inhibitor. Samples were centrifuged at 2000 X g for 25 min, and plasma glucose was measured using a Technicon Autoanalyzer System (Technicon Instruments, Inc., Tarrytown, NY). Total chewing, eating, and ruminating times were recorded during wk 4 of each period. The chewing action of individual cows was observed and recorded every 5 min during 24 h. Rate of rumination (chews per bolus) was determined by observing individual cows during bouts of rumination. Although not an absolute measurement, this method of scan sampling yields reliable estimates given the short interval between observations (28). Rumination activity (minutes per kilogram of DM and fiber intake) was determined. Data were analyzed as a replicated 4 x 4 Latin square (1) using the general linear models procedure of SAS (23) with a factorial arrangement of treatments. Orthogonal comparisons were 1) fine silage versus fine silage Journal of Oairy Science Vol. 75, No. 10, 1992
plus chopped hay, 2) WRS fed at 0 or 11.6% of dietary DM, and 3) interaction between physical form of silage and addition of WRS. Unless otherwise stated, statistical significance was determined at P < .10. Trial 2
Cows and Treatments. Eight early lactation Holstein cows (four primiparous) were used in a replicated 4 x 4 Latin square design. Cows averaged 17 DIM (± 7 d) when they were randomly assigned to dietary treatments. Dietary treatments were 1) low fiber (LF), 25% NDF with 11.6% WRS (LF + WRS); 2) 25% NDF without WRS (LF - WRS); 3) high fiber (HF), 29% NDF with 11.6% WRS (HF + WRS); and 4) 29% NDF without WRS (HFWRS). All diets were fed as TMR and were formulated to be nearly isocaloric within a fiber percentage and isonitrogenous (18.0% CP). As formulated, diets HF + WRS and HF - WRS had .03 and .05 Mcal of NEdkg less than diets LF + WRS and LF - WRS. On a DM basis, diets LF + WRS and LF - WRS contained 39% forage (AS and com silage), and diets HF + WRS and HF - WRS contained about 49% (Table 2). All other aspects of
2745
DIETARY FAT AND FIBER TABLE 2. Composition of rations differing in fitw percentage and soybean addition for trial 2. Dietl Item
LF + WRS
LF - WRS
DM,%
67.9
68.9
65.3 (% of DM)
64.0
CP ADF NDF EE2 NEL,3 Mca1lkg
17.5 14.2 25.0 5.7 1.78
17.8 14.4 25.5 3.5 1.77
17.8 17.1 28.8 5.7 1.75 (% composition, DM basis)
17.9 17.4 29.1 3.4 1.73
Alfalfa silage Corn silage Shelled corn Soybean meal, 44% CP Whole raw soybeans Vitamin-mineral supplement4
19.5 19.5 40.0 6.8 11.7 2.5
19.7 19.7 42.4 15.7 2.5
HF + WRS
24.3 24.3 30.9 6.6 11.6 2.3
HF - WRS
24.8 24.8 33.4 14.7 2.3
lLF = Low fiber, 25% NDF ration; HF = high fiber, 29% NDF ration, WRS = whole raw soybeans. 2EE = Ether extract. 3Calculated form NRC (18). 4Vitamins and minerals were formulated to meet or to exceed requirements according to NRC (18).
design, sample collection, analyses, and statistical treatment of results were identical to those of trial 1. RESULTS AND DISCUSSION
Addition of WRS to a diet changes not only the fat but also the proportion of escape protein (18). In an effort to avoid protein effects on cow performance among diets, diets were formulated to contain 18.5% CP with 33 to 34% of CP as undegraded intake protein using estimates of protein degradability given by NRC (18). Replacement of a portion of the corn and soybean meal with WRS allowed all diets to remain nearly isocaloric in trial 1. Because diets essentially were isocaloric in trial 1, performance responses were interpreted as being due to fiber particle size or to WRS addition. In trial 2, addition of 11.6% WRS increased EE from 3.5 to 5.7%. Diets were formulated to contain 18% CP with 35 to 38% undegraded intake protein in an effort to minimize effects of source of soybean CP on cow performance. Because diets essentially were isocaloric at an NDF percentage, as in trial 1, cow responses in trial 2 were interpreted as being due to NDF (or energy) percentage or WRS addition.
Addition of ASH increased the mean particle size of diets ASH + WRS and ASH - WRS in trial 1 (Table 3). In trial 2, particle size actually was smaller for the higher NDF than for the lower NDF diets. Both simple arithmetic and geometric mean particle sizes were calculated. Calculation of an arithmetic mean particle size requires no assumptions concerning the sample particle distribution, but determination of a geometric mean particle size assumes thai the distribution of feed particles is log normal (27). Although the validity of this assumption may be questioned when particle size of coarsely chopped forages is measured (12), calculation of geometric mean particle size allows more extensive comparison with reported literature (27). Geometric mean particle sizes consistently were smaller than the arithmetic mean particle sizes for all forages and diets (Table 3). Furthermore, addition of WRS increased the mean particle size of TMR because of entrapment of WRS on the larger screen sizes (~3.35 mm). This interaction of whole grains and measurement of dietary particle size has been discussed (12). Particle distribution of forages is depicted in Figure 1 to complete the description of dietary particle size. Chopped alfalfa hay contained 81 % of particles >1.18-rom screen size Journal of Dairy Science Vol. 75, No. 10, 1992
2746
GRANT AND WEIDNER
TABLE 3. Particle sizes of forages and rations fed during trials 1 and 2.
Sample!
Arithmetic mean particle size
Geometric mean particle size 2
Logarithmic SD
(mm)
Recovery3 (%)
Trial I AS Alfalfa hay AS + WRS AS - WRS ASH + WRS ASH - WRS
3.01 3.30 3.48 3.01 3.56 3.34
1.89 2.19 2.81 2.50 2.84 2.60
Trial 2 AS Com silage LF + WRS LF - WRS HF + WRS HF - WRS
3.01 4.97 4.14 3.45 4.07 3.56
1.89 4.28 3.05 2.43 2.91 2.27
.14 .18
.11 .19 .16 .10 .14
.11 .15 .17 .16 .17
99.0 99.1 99.0 99.8 99.9 99.7 99.0 98.9 99.6 99.1 99.8 99.7
1AS = Alfalfa silage (finely chopped); ASH = alfalfa silage plus coarsely chopped alfalfa hay; WRS = whole raw soybeans; LF = low fiber, 25% NDF ration; HF = high fiber, 29% NDF ration.
2Calculated according to Waldo et al. (27). 3Recovery of original sample on sieves when weighed.
and com silage nearly 83% compared with AS, which contained only 47% of particles >1.18mm screen size (Figure 1). Particles retained on the ~ 1. 18-mm screen required rumination and particle size reduction for passage from the reticulorumen in sheep (21). The critical size for escape in dairy cattle is likely closer to the 2.36-mm screen size (12). In trial 1, diet ASH - WRS contained 32% more particles >2.36mm screen size than did diet AS - WRS. Therefore, considerably more potential existed for rumination on the coarse forage diets (ASH + WRS and ASH - WRS) than on the finer forage diets (AS + WRS and AS - WRS) in trial 1. In trial 2, dietary particles retained on the ~2.36-mm screen were similar for all diets (54% for LF, HF - WRS; 65% for LF, HF + WRS). Therefore, altered rumination activity should have been due to NDF percentage or WRS addition and not due to differences in forage particle size for trial 2.
7.1% and reduced forage and ADF intakes as percentages of BW by 10.5 and 10.0%, respectively, for AS diets. As expected, EE intake increased from .76 to 1.10 kgld with WRS addition. Similar to other research with lactating dairy cows fed alfalfa-based rations (12), no effects of forage particle size on DMI or
OMI and Fiber Intake
Figure 1. Particle distributions of alfalfa silage, chopped alfalfa hay. and com silage used in trials 1 and 2 as determined by dry sieving. Chopped alfalfa hay contained 81 % of particles > U8-mm screen size, com silage had 83% >U8-mm screen size, and alfalfa silage had 47% >1.18-mm screen size.
Table 4 presents DMI and fiber intake for trials 1 and 2. In trial 1, addition of 11.6% WRS decreased daily DMI by approximately Journal of Dairy Science Vol. 75. No. 10, 1992
30
•
1
Com silage
m
Alfalfa silage
[J Chopped ""alia hay
6.30 >9.50
DIETARY FAT AND FIBER
2747
TABLE 4. Intake of DM components as influenced by fiber percentage, particle size, and supplemental fat from whole raw soybeans.\
Component Total DMI kg/d··c.d.• % of BW·.b,c.d,e Forage DMI kg/d·.c,d.• % of BW··b.c.d,e ADF Intake kg/da,c.d.• % of BW··b,c.d.• NDF Intake kg/da,c.d.• % of BW··c.d,e EE3 Intake kg/da,d % of BW··d
Trial ]2 AS AS ASH ASH + WRS - WRS + WRS - WRS
Trial 2 LF
SE
LF
HF
HF
+ WRS - WRS + WRS - WRS
SE
18.4 3.3
20.0 3.6
18.4 3.3
19.6 3.4
.8 .1
22.2 3.7
25.4 4.2
22.0 3.7
23.0 3.9
.6
