Effect of Grain Level and Protein Source on Ruminal Fermentation, Degradability, and Digestion in Milking Cows Fed Silage1 HELENE V. PETIT Lennoxville Research Station, Agriculture Canada PO BOX 90 Lennoxville, PO, Canada J1M 1Z3 D. M. VEIRA Animal Research Centre, Agriculture Canada Ottawa, ON, Canada K1A oce ABSTRACT
(60%). Generally, feeding concentrate at 1.3 or 1.8% BW and supplementing with soybean meal or fish meal resulted in pH and concentrations of NH3 N and VFA similar to those observed on the all silage diet. Feeding concentrate at 1.3 or 1.8% BW and supplying fish meal or soybean meal did not change feed utilization enough to increase milk production in low producing cows compared with an all silage diet. (Key words: alfalfa silage, feeding level, digestibility)
Five primiparous Holstein cows (483 kg BW) of low productivity were used in a 4 x 5 incomplete Latin square design to study the effects of feeding two levels of grain containing soybean meal and one level of grain containing fish meal on feed intake, milk production, digestibility, and rumen fennentation. Animals all were fed alfalfa silage for ad libitum intake. Collection of data was between wk 11 and 24 of lactation. The four treatments were an all silage diet (control), silage and medium concentrate fed at 1.8% BW containing soybean meal, and silage and low concentrate fed at 1.3% BW containing either soybean meal or fish meal. Treatments other than control were designed to give similar CP intake from the concentrate, which was based on high moisture com and cob meal. Milk production and composition were similar among treatments except for fat percentage, which was significantly lower for low grain soybean meal. Intake of OM was higher on medium grain soybean meal compared with the other treatments. Average BW and change in BW (.11 kg/d) were not affected by treatments. Digestibility of DM was higher for cows fed grain (68 to 73%) than for those fed the control diet
Abbreviation key: DMS = OM solubilized at time zero, EDDM = effective degradability of OM, HMEC = high moisture ear com, LFM = low level concentrate containing fish meal, LSBM =low level concentrate containing soybean meal, MSBM = medium level concentrate containing soybean meal, PDM = potentially degradable OM, RD = rate of disappearance, SIL = all silage diet. INTRODUCTION
Received November 9. 1990. Accepted February 12, 1991. 'Contribution Number 305 from the LeDnoxville ROo search Station. Contribution Number 1720 from the Animal Research Cenlre. 1991 ] Dairy Sci 74:2256-2267
Low microbial protein synthesis in the rumen was observed when feeding alfalfa silage to ruminants (36), which resulted in reduced availability of protein for digestion. Thus, feeding only high moisture alfalfa silage would not meet requirements for undegradable protein intake of dairy cows (19). This is corroborated by the fact that feeding low rumen degradable protein increases milk yield of early lactating and high producing cows (4) and of cows in negative energy balance (8, 23). Moreover, small amounts of low rumen degradable protein, such as fish meal, were as effective as large amounts of grain in promoting milk production in multiparous cows aver-
2256
2257
PROTEIN SOURCE AND ALFALFA Sn.AGE TABLE 1. Composition of feed ingredients. AHaifa
High moisture
Item
silage
ear com
pH DM.% OM, % OM ADF. % DM NDF. % DM cp. % OM Protein N. % total N NH3 N. % total N Gross energy, kcaIIg DM Lactic acid. % DM Acetic acid, % DM Propionic acid. % DM Butyric acid. % DM Ethanol. % DM K. % DM Ca. % DM p. % DM Mg. % OM Cu. mgIkg DM Zn, mgIkg DM Mn, mg/kg OM Fe. mgIkg DM
520 28.4 88.9 31.2 43.9 19.9 40.1 9.4 4.3 4.9 2.8 .1 .1 .2 2.65 1.22 .39 .24 11.11 37.38 51.05 614.7
4.47 60.0 97.8 10.0 22.7 8.4 65.7 2.0 4.3 3.1 .2 0 0 .6 .54
aging 23.8 kg/d of milk and fed grass silage containing theoretically adequate levels of CP (26). This suggests that grain level in the diet of mid or late lactation cows could be decreased by feeding low amounts of low rumen degradable protein. Improvement in animal perfonnance observed after feeding a low rumen degradable protein was related to increased flow of CP reaching the duodenum (1) and improved digestibility of the diet (21). Feeding slowly compared with rapidly degradable concentrate protein allowed a more stable fennentation, which resulted in a higher acetate to propionate ratio in the rumen (35). This was attributed to a slow release of available N in the rumen and the presence of amino acids and peptides which favor the development of rumen microflora and cellulose digestion (21). However, no data are available on the changes in feed utilization for low producing primiparous cows fed an all alfalfa silage diet containing low amounts of undegradable protein and supplemented with various levels of concentrate and proteins of different degradability. Moreover, it is not known if CP requirements of such cows can be met by feeding only alfalfa silage cut at the bud stage. The objec-
.04 .31 .Ll 8.88 35.64 7.81 55.58
Soybean meal
Fish meal
90.6 94.0 6.1
95.6 73.9 1.0
54.5 852
61.5 88.1
4.6
4.1
2.38 .22 .65 .30 (8.49 85.43 33.31 255.9
.46 7.41 2.]4 .23 4.]6 51.62 9.78 305.4
tives of this experiment were to detennine the effects of feeding an all silage diet, a medium or low level of concentrate containing soybean meal, or a low level of concentrate containing fish meal on ruminal fennentation characteristics, in situ OM degradability, and apparent digestibility in low producing primiparous cows. This experiment was conducted in parallel with a production trial using multiparous cows of higher milk production, and results have been presented in a prior paper (25). MATERIALS AND METHODS Animals and Feeding
Five rumen .10) among treatments (Table 7) and were above minimum requirements for maximal rate of fermentation (16). Higginbotham et aI. (12) also observed no effect of protein degradability on concentration of NH3 N. On the other hand, Waltz et al. (37) reported higher NH3 N concentrations for cows fed soybean meal compared with those fed lower mmen degradable protein. Differences observed in NH3 N concentrations might be due to the high amount of soybean meal fed (17.0% of DM) in the experiment of Waltz et al. (37) compared with the low level used in
2263
PROTEIN SOURCE AND ALFALFA Sn.AGE
TABLE 6. Energy partition in primiparous cows fed 8 medium (MSBM) or low (LSBM) level of concentrate containing soybean meal, a low level of coocentrate containing fish meal (lFM), or silage alone (Sll..). Treatment Item
MSBM
LSBM
LFM
Sll..
NEL Intake,l McaJId Milk oUlpl1t NEL? McaJ/d Maintenance ~,3 Mcal/d Difference NE[} Mcal/d Calculated BW c~e,s kg/d Actual BW change, ¥J.d Dietary required NEL. Mcal/d
26.6 12.5
22.2 125
22.5
15.2 11.8 9.9
9.9 4.2 .82
9.9 -.2 -.04
.32 24.1
.29 23.9
12.2 9.8 .5 .10 -.14 21.3
~.5
-1.32 -.05 21.5
lCalculated using energy digestibility data and equations published by NRC (19). 2calculated using equations of Tyrrell and Reid (34). 3Values from NRC (19). 40ifference between energy intake and output (milk production plus maintenance).
~ased upon the difference and the NEL given for BW change during lactation (19). = .26; P = .5.
6SE
7Calculated from NRC (19) and Tyrrell and Reid (34), including requirements for maintenance, milk production, and the actual BW change observed in the experiment
this study (less than 6.5% of OM). On the other hand, Ha and Kennelly (11) obtained similar NH3 N values when canola and fish meal were fed at 17.3 and 9.0% of OM, respectively, and ZeIbini et at (38) noted higher pH and lower NH3 N concentration when fish meal was fed at 12.9% of OM compared with soybean meal at 17.9% of OM. The small amounts of protein supplements fed in this experiment, 0, 2.9, 4.8, and 6.4% of OM for SIL, MSBM, LFM, and LSBM, respectively, were not different enough to affect pH and NH3 N concentrations. Concentration of NH3 N increased for all treatments after feeding silage (Figure 2). Feeding HMEC at 2 h decreased the NH3 N concentrations for MSBM and LSBM cows fed soybean meal as the main source of protein. Cows on LFM tended to maintain higher concentrations of NH3 N after HMEC was fed, which was unexpected. The pattern of NH3 N concentrations was similar to that reported by Veen et al. (35). Total VFA concentrations in ruminal fluid (fable 7) were similar for all treatments. Higher concentrations of total VFA were reported previously by ZeIbini et al. (38) when cows were fed soybean meal rather than fish meal, whereas Ha and KenneUy (11) found similar total VFA concentrations for protein of
low and high degradability. Concentrations of total VFA increased (P < .05) over time for treatments containing concentrate, as noted also by Veen et al. (35), but total VFA concentrations remained constant after feeding for the all silage diet (data not shown). The average molar percentage of acetate (fable 7) tended to be higher (P = .05) for SIL (68.2%) and lower for LFM (64.4%). Higginbotham et al. (12) observed a reduction in rumen acetate when protein degradability was decreased. The average molar percentages of propionate, isobutyrate, butyrate, and isovalerate (fable 7) were not different (P > .10) among treatments. Molar proportion of valerate was significantly higher (P < .05) for LFM (2.3%) than for other treatments (1.9 to 2.0%). lbe acetate to propionate ratio was similar (P > .05) for all treatments (fable 7). Determined OM solubilized at t = 0 (
(60%). Generally, feeding concentrate at 1.3 or 1.8% BW and supplementing with soybean meal or fish meal resulted in pH and concentrations of NH3 N and VFA similar to those observed on the all silage diet. Feeding concentrate at 1.3 or 1.8% BW and supplying fish meal or soybean meal did not change feed utilization enough to increase milk production in low producing cows compared with an all silage diet. (Key words: alfalfa silage, feeding level, digestibility)
Five primiparous Holstein cows (483 kg BW) of low productivity were used in a 4 x 5 incomplete Latin square design to study the effects of feeding two levels of grain containing soybean meal and one level of grain containing fish meal on feed intake, milk production, digestibility, and rumen fennentation. Animals all were fed alfalfa silage for ad libitum intake. Collection of data was between wk 11 and 24 of lactation. The four treatments were an all silage diet (control), silage and medium concentrate fed at 1.8% BW containing soybean meal, and silage and low concentrate fed at 1.3% BW containing either soybean meal or fish meal. Treatments other than control were designed to give similar CP intake from the concentrate, which was based on high moisture com and cob meal. Milk production and composition were similar among treatments except for fat percentage, which was significantly lower for low grain soybean meal. Intake of OM was higher on medium grain soybean meal compared with the other treatments. Average BW and change in BW (.11 kg/d) were not affected by treatments. Digestibility of DM was higher for cows fed grain (68 to 73%) than for those fed the control diet
Abbreviation key: DMS = OM solubilized at time zero, EDDM = effective degradability of OM, HMEC = high moisture ear com, LFM = low level concentrate containing fish meal, LSBM =low level concentrate containing soybean meal, MSBM = medium level concentrate containing soybean meal, PDM = potentially degradable OM, RD = rate of disappearance, SIL = all silage diet. INTRODUCTION
Received November 9. 1990. Accepted February 12, 1991. 'Contribution Number 305 from the LeDnoxville ROo search Station. Contribution Number 1720 from the Animal Research Cenlre. 1991 ] Dairy Sci 74:2256-2267
Low microbial protein synthesis in the rumen was observed when feeding alfalfa silage to ruminants (36), which resulted in reduced availability of protein for digestion. Thus, feeding only high moisture alfalfa silage would not meet requirements for undegradable protein intake of dairy cows (19). This is corroborated by the fact that feeding low rumen degradable protein increases milk yield of early lactating and high producing cows (4) and of cows in negative energy balance (8, 23). Moreover, small amounts of low rumen degradable protein, such as fish meal, were as effective as large amounts of grain in promoting milk production in multiparous cows aver-
2256
2257
PROTEIN SOURCE AND ALFALFA Sn.AGE TABLE 1. Composition of feed ingredients. AHaifa
High moisture
Item
silage
ear com
pH DM.% OM, % OM ADF. % DM NDF. % DM cp. % OM Protein N. % total N NH3 N. % total N Gross energy, kcaIIg DM Lactic acid. % DM Acetic acid, % DM Propionic acid. % DM Butyric acid. % DM Ethanol. % DM K. % DM Ca. % DM p. % DM Mg. % OM Cu. mgIkg DM Zn, mgIkg DM Mn, mg/kg OM Fe. mgIkg DM
520 28.4 88.9 31.2 43.9 19.9 40.1 9.4 4.3 4.9 2.8 .1 .1 .2 2.65 1.22 .39 .24 11.11 37.38 51.05 614.7
4.47 60.0 97.8 10.0 22.7 8.4 65.7 2.0 4.3 3.1 .2 0 0 .6 .54
aging 23.8 kg/d of milk and fed grass silage containing theoretically adequate levels of CP (26). This suggests that grain level in the diet of mid or late lactation cows could be decreased by feeding low amounts of low rumen degradable protein. Improvement in animal perfonnance observed after feeding a low rumen degradable protein was related to increased flow of CP reaching the duodenum (1) and improved digestibility of the diet (21). Feeding slowly compared with rapidly degradable concentrate protein allowed a more stable fennentation, which resulted in a higher acetate to propionate ratio in the rumen (35). This was attributed to a slow release of available N in the rumen and the presence of amino acids and peptides which favor the development of rumen microflora and cellulose digestion (21). However, no data are available on the changes in feed utilization for low producing primiparous cows fed an all alfalfa silage diet containing low amounts of undegradable protein and supplemented with various levels of concentrate and proteins of different degradability. Moreover, it is not known if CP requirements of such cows can be met by feeding only alfalfa silage cut at the bud stage. The objec-
.04 .31 .Ll 8.88 35.64 7.81 55.58
Soybean meal
Fish meal
90.6 94.0 6.1
95.6 73.9 1.0
54.5 852
61.5 88.1
4.6
4.1
2.38 .22 .65 .30 (8.49 85.43 33.31 255.9
.46 7.41 2.]4 .23 4.]6 51.62 9.78 305.4
tives of this experiment were to detennine the effects of feeding an all silage diet, a medium or low level of concentrate containing soybean meal, or a low level of concentrate containing fish meal on ruminal fennentation characteristics, in situ OM degradability, and apparent digestibility in low producing primiparous cows. This experiment was conducted in parallel with a production trial using multiparous cows of higher milk production, and results have been presented in a prior paper (25). MATERIALS AND METHODS Animals and Feeding
Five rumen .10) among treatments (Table 7) and were above minimum requirements for maximal rate of fermentation (16). Higginbotham et aI. (12) also observed no effect of protein degradability on concentration of NH3 N. On the other hand, Waltz et al. (37) reported higher NH3 N concentrations for cows fed soybean meal compared with those fed lower mmen degradable protein. Differences observed in NH3 N concentrations might be due to the high amount of soybean meal fed (17.0% of DM) in the experiment of Waltz et al. (37) compared with the low level used in
2263
PROTEIN SOURCE AND ALFALFA Sn.AGE
TABLE 6. Energy partition in primiparous cows fed 8 medium (MSBM) or low (LSBM) level of concentrate containing soybean meal, a low level of coocentrate containing fish meal (lFM), or silage alone (Sll..). Treatment Item
MSBM
LSBM
LFM
Sll..
NEL Intake,l McaJId Milk oUlpl1t NEL? McaJ/d Maintenance ~,3 Mcal/d Difference NE[} Mcal/d Calculated BW c~e,s kg/d Actual BW change, ¥J.d Dietary required NEL. Mcal/d
26.6 12.5
22.2 125
22.5
15.2 11.8 9.9
9.9 4.2 .82
9.9 -.2 -.04
.32 24.1
.29 23.9
12.2 9.8 .5 .10 -.14 21.3
~.5
-1.32 -.05 21.5
lCalculated using energy digestibility data and equations published by NRC (19). 2calculated using equations of Tyrrell and Reid (34). 3Values from NRC (19). 40ifference between energy intake and output (milk production plus maintenance).
~ased upon the difference and the NEL given for BW change during lactation (19). = .26; P = .5.
6SE
7Calculated from NRC (19) and Tyrrell and Reid (34), including requirements for maintenance, milk production, and the actual BW change observed in the experiment
this study (less than 6.5% of OM). On the other hand, Ha and Kennelly (11) obtained similar NH3 N values when canola and fish meal were fed at 17.3 and 9.0% of OM, respectively, and ZeIbini et at (38) noted higher pH and lower NH3 N concentration when fish meal was fed at 12.9% of OM compared with soybean meal at 17.9% of OM. The small amounts of protein supplements fed in this experiment, 0, 2.9, 4.8, and 6.4% of OM for SIL, MSBM, LFM, and LSBM, respectively, were not different enough to affect pH and NH3 N concentrations. Concentration of NH3 N increased for all treatments after feeding silage (Figure 2). Feeding HMEC at 2 h decreased the NH3 N concentrations for MSBM and LSBM cows fed soybean meal as the main source of protein. Cows on LFM tended to maintain higher concentrations of NH3 N after HMEC was fed, which was unexpected. The pattern of NH3 N concentrations was similar to that reported by Veen et al. (35). Total VFA concentrations in ruminal fluid (fable 7) were similar for all treatments. Higher concentrations of total VFA were reported previously by ZeIbini et al. (38) when cows were fed soybean meal rather than fish meal, whereas Ha and KenneUy (11) found similar total VFA concentrations for protein of
low and high degradability. Concentrations of total VFA increased (P < .05) over time for treatments containing concentrate, as noted also by Veen et al. (35), but total VFA concentrations remained constant after feeding for the all silage diet (data not shown). The average molar percentage of acetate (fable 7) tended to be higher (P = .05) for SIL (68.2%) and lower for LFM (64.4%). Higginbotham et al. (12) observed a reduction in rumen acetate when protein degradability was decreased. The average molar percentages of propionate, isobutyrate, butyrate, and isovalerate (fable 7) were not different (P > .10) among treatments. Molar proportion of valerate was significantly higher (P < .05) for LFM (2.3%) than for other treatments (1.9 to 2.0%). lbe acetate to propionate ratio was similar (P > .05) for all treatments (fable 7). Determined OM solubilized at t = 0 (
