Feeding Peas to Dairy Cattle and the Effects on the Rumen
Peas may provide better dairy production
for cows fed cereal hay based diets by promoting a more stable
rumen environment. Supplementing hay diets with high levels of
barley grain in dairy cow diets causes major changes in rumen
fermentation. This leads to digestive disorders, reductions in
hay intake and losses in milk production due to the rapid fermentation
of starch to volatile fatty acids and lactic acid. The result
is a low rumen pH (below 5.8) and a severe inhibition of cellulolysis.
Rumen bacteria normally associated with fiber digestion are almost
eliminated when this occurs (Valentine and Bartsch 1987 {652};
Bartsch and Valentine 1986 {658}). Replacement of barley with
peas (and other legumes) as 70% of the total ration administered
twice daily to cows resulted in a rumen pH that was significantly
higher three to six hours after the feed was administered. The
rumen pH did not fall below 6.0 in contrast to barley (including
2% urea) fed cows. When barley was supplemented the rumen pH
was below 6.0 for approximately 7 hr of the 12 hr feeding period
(Bartsch and Valentine 1986 {658}).
Ammonia-nitrogen concentrations
Rumen ammonia-nitrogen concentration in the rumen of the cows offered hammermilled barley grain with 2% urea was below 5mg/100 mls for 7 hours of the 12 hr feeding interval. Replacing barley with legume grains (including peas) resulted in higher ammonia-nitrogen concentrations at 0, 3, 4, 5, 6 and 8 hr in comparison to barley. Rumen ammonia-nitrogen concentrations below 5 mg 100/ml are sub-optimal for maximum bacterial protein synthesis by the less competitive cellulolytic bacteria (Pisulewske et al. 1981 as cited by Valentine and Bartsch 1987 {652}).
Volatile Fatty Acid Concentrations (VFA)
There were no differences in the concentration and the proportion of volatile fatty acids between Friesian cows supplemented with hammermilled lupin, pea, faba bean or barley grain. The volatile fatty acid (VFA) concentration of cows supplemented with barley and peas were not different (90.8 and 102.4 mM), respectively. The VFA proportion for cows fed barley were 59.5% acetic, 26.5% propionic and 14.0% butyric. The VFA proportion for cows supplemented with peas were the same for acetic (58.3%) and propionic (26.5%), but was higher (P < 0.05) for butyric (20.3%). Production response and rumen characteristics suggest that grain legumes are less likely to cause problems than cereal grains when introduced suddenly into a diet (Bartsch and Valentine 1986 {658}; Valentine and Bartsch 1987 {652}).
| Table 5. Chemical composition of concentrate mixtures and milk production and composition of cows fed pea or SBM/CM supplemented dietsz | |||
|---|---|---|---|
| Chemical composition | SBM\CM based | Pea based | Standard error |
| DM% | 89.8 | 89.7 | |
| % of DM | |||
| CP | 18.5 | 18.5 | |
| ADF | 7.3 | 7.4 | |
| NDF | 13.4 | 13.6 | |
| Crude fat | 5.2 | 4.5 | |
| NEL | 1.75 | 1.76 | |
| Performance of all cows (n = 155, 108 and 109 for cows in early, mid- and late-lactation periods) | |||
| Production (kg/d) | |||
| Milk | 32.1a | 30.5b | 0.54 |
| Fat | 0.97a | 1.03b | 0.02 |
| Protein | 0.96 | 0.94 | 0.02 |
| FCM | 27.4 | 27.8 | 0.45 |
| Milk composition (%) | |||
| Fat | 3.13a | 3.48b | 0.06 |
| Protein | 3.01 | 3.11 | 0.04 |
a-b
means in the same row with different letters are different (P<0.05).
zAdapted from Corbett et al. 1995 {562}.