Forage pH Effects on Intake in Early Lactation Dairy Cows

In Experiment 1, 18 mature Holstein cows were used in a single reversal design with 6-wk periods from wk 5 to 16 postpartum. Cows were fed for ad libitum consumption corn silage and grain separately in a 40:60 ratio where treatments consisted of a corn silage (pH = 3.64) or corn silage partially neutralized with sodium bicarbonate prior to feeding (pH = 5.44). Neutralization of corn silage increased forage DM intake 1.0 kg/d and total DM 1.3 kg/d. Milk fat percent was increased from 3.79 to 4.15. In Experiment 2, 17 mature Holstein cows were used in an identical design except that alfalfa haylage was used as the forage. Increasing alfalfa haylage pH from 4.62 to 5.45 had no effect on intake or milk production. Literature data means and data summarized from the present experiments in multiple regression analysis indicated that intake as a percentage of body weight = .96 + .88 pH - .077 pH2 (R2 = .65, n = 49). Optimal pH for maximum intake was 5.7. Intake responses to pH above 4.5 are relatively small and explain the differences in responses seen between corn silage and alfalfa haylage in Experiments 1 and 2.