Raw Soybeans and Roasted Soybeans of Different Particle Sizes. 1. Digestibility and Utilization by Lactating Cows

Abstract

This study examined effects of dietary whole raw soybeans and roasted soybeans of different particle sizes on digestibility and performance of lactating cows. Five cows with ruminal and duodenal cannulas were used in a 5 × 5 Latin square design. Diets contained 55% corn silage and 45% concentrate. Treatments were control and whole raw, whole roasted, cracked roasted, and ground roasted soybeans. All soybean diets contained 19.7% soybeans (DM basis). Roasted soybeans fed to cows decreased ruminal NH3 N and branched-chain VFA. Apparent N disappearance from the intestines tended to be higher (percentage of duodenal flow) for cows fed whole roasted soybeans than for those fed whole raw soybeans. Roasting increased the undegraded protein of soybeans. Roasted soybeans increased milk yield but had no effect on milk composition compared with raw soybeans. Decrease in the particle size of whole roasted soybeans tended to increase intestinal digestion of N (percentage of duodenal flow) but may have decreased undegraded protein of soybeans. Milk yield and composition were not affected by particle size of roasted soybeans. Dietary whole or cracked roasted soybeans to dairy cows are recommended when soybeans are fed as a relatively high proportion of dietary DM or when undegraded intake protein is limiting in the diet. © 1993, American Dairy Science Association. All rights reserved.