HYDROLYZED SOY PROTEIN ISOLATE SUSTAINS HIGH NUTRITIONAL PERFORMANCE IN VEAL CALVES

Milk replacers containing skim milk powder or a mixture of whey and so y protein provided by a hydrolyzed soy protein isolate or a heated soy bean flour were fed to 1-mo-old calves for 101 d. The isolate and the flour provided 56 and 72% of dietary proteins, respectively. Digestibi lity of feed constitutents was measured between 9 to 14 d and 65 to 70 d of treatment. Digestive function was evaluated by measurement of ru minal pH, plasma kinetics of triglyceride and glucose concentrations, and xylose absorption. Antibody production was also recorded. Growth a nd carcass characteristics were satisfactory for the control diet and the diet based on soy isolate, partly because of high apparent digesti bility of protein and lack of antibody synthesis in response to soy is olate. In contrast, protein from soybean flour was poorly digested and highly immunogenic. Ruminal pH at 2.5 h after the meal was unaffected by dietary treatments. Postprandial changes in concentrations of trig lycerides and glucose in plasma suggested a lack of abomasal clotting with both diets based on soy. Xylose concentration in plasma was only slightly affected by dietary treatment and calf age. Hydrolyzed soy pr otein is suitable for veal calves and can account for at least half of protein intake.