EFFECTS OF NEUTRALIZING ACID WHEY POWDER IN MILK REPLACERS CONTAINING MILK AND SOYBEAN PROTEINS ON PERFORMANCE AND ABOMASAL AND INTESTINAL DIGESTION IN CALVES

Abstract

Milk replacers with relatively low pH result from the inclusion of acid whey powder in the formula. Experiments were carried out to determine the effects of adjusting the pH of milk replacers containing different levels of acid whey and milk (M) or milk and soybean proteins (MS) on calf performance. Weight gains of calves to 8 weeks of age were increased by 15% (P < 0.20) in two experiments when the pH of the M diet with 23% whey powder was adjusted from about 5.7 to 6.8 with NaOH. Digestible nutrient intakes per unit weight gain decreased by about 15% (P < 0.10), but digestion coefficients were not significantly affected. Results from four calves with abomasal or reentrant intestinal cannulas indicated that the beneficial response to pH adjustment was due to a slower rate of abomasal emptying. Compared with the unadjusted diets, pH adjustment resulted in a greater drop in pH and higher nitrogen content (mg/ml) in abomasal digesta, and reduced volume flow, nitrogen, trypsin, and chymotrypsin in intestinal digesta. The calf responses to pH adjustment were less with the MS compared with the M diets containing 23% whey powder. Adjusting the pH of the M diet containing 52% acid whey powder from 5 to 6.8 had no effect on calf growth or nutrient utilization. The nitrogen supplied by the whey powder was calculated to be only 50% digestible by calves at 3–4 weeks of age. Proteolytic enzyme secretion from the pancreas was about 2.5 times less on the 52% compared with the 23% whey formula. We conclude that acid whey powder can be added to milk replacers at levels of about 23 % and that adjusting the pH improves calf performance.