Effects of Roasting, Extrusion, and Particle Size on the Feeding Value of Soybeans for Dairy Cows

Abstract

Ten multiparous Holstein cows were assigned to a replicated 5 × 5 Latin square (21-d periods) approximately 116 d postpartum. Squares one and two averaged 36.4 and 24.4 kg of 4% FCM/d, respectively. Diets contained 45.1% alfalfa silage, 9.2% corn silage, and 45.7% concentrate (DM basis) fed for ad libitum intake as a TMR. Treatments were 1) rolled raw soybeans, 2) finely ground raw soybeans, 3) diet 2 with distillers dried grains, 4) roasted soybeans, and 5) extruded soybeans. Treatments 1, 2, 4, and 5 contained 15.7% of the ration DM as soybeans, averaging 4.1 kg/d of soybean DMI. Treatment 3 contained 12.6% of the ration DM as soybeans, with an average intake of 3.2 kg/d of soybeans. Yields of FCM, milk fat and protein, fat percentage, DMI, and rates of DM and NDF disappearance were not significantly affected by treatment. Milk protein percentage was highest for diet 1 and lowest for diets 4 and 5. Apparent digestibilities of nutrients in the whole tract usually were highest for cows receiving treatment 1. Fatty acid digestibility was depressed on diet 4. Rumen VFA and pH were not different, except that propionate concentrations and acetate:propionate ratios were highest for diets 4 and 5. However, acetate:propionate ratios never fell below 3.4 for any diet. Although roasting depressed apparent digestibility of fatty acids, processing of soybeans had little effect on lactation performance of dairy cattle. © 1991, American Dairy Science Association. All rights reserved.