Influence of Substituting Two Types of Soybean Protein for Milk Protein on Gain and Utilization of Milk Replacers in Calves

Abstract

Twenty-four male calves (8/treatment) were fed milk replacers containing 19% crude protein from: a) 100% milk protein; b) 66% modified soybean protein plus 34% milk protein; c) 66% heated soybean flour plus 34% milk protein as the only nutrients at 8, 9, 10, 11, 12, 12, 12, and 12% body weight from 1 to 8 wk of age, respectively. Milk protein resulted in faster gains and improved feed efficiencies. Organic matter and crude protein digestibilities for milk replacers containing all milk protein, modified soybean protein, and heated soybean flour at 5 wk of age were 90.8, 87.2, and 85.3%; 82.6, 72.1, and 64.1%, respectively. Xylose absorption performed on d 50 by oral dosing of .5 g D-xylose/kg weight, and xylose disappearance performed on d 44 by intravenous injection of .25 g D-xylose/kg weight showed 16% greater xylose absorption for milk than modified soybean protein or heated soybean flour. Calves fed soybean protein cleared xylose faster from the blood. Two calves per treatment were sacrificed for electron microscopic evaluation of intestinal tissue. Greater morphological variation in size and shape of villi was observed within animals than among treatments. These data suggest that the superior performance of calves fed milk compared with soy protein is related to a greater digestibility and absorptive capacity of digested nutrients. © 1986, American Dairy Science Association. All rights reserved.