Relation of Intake to Digestibility of Diets Containing Soyhulls and Distillers Dried Grains

Abstract

Fifty-four multiparous Holstein cows were used to compare the influence of intake on digestibility of three diets. All diets contained a 50:50 ratio (dry basis) of ammoniated corn silage and concentrate. The control concentrates consisted of corn, oats, and soybean meal. The two test concentrates contained either 43.8% soyhulls or 71.6% corn distillers dried grains with solubles. Each diet was fed at three intakes. Dry cows were fed one times maintenance intake, cows producing 10 to 20 kg milk daily were fed at twice maintenance, and cows producing 27 to 49 kg daily were fed ad libitum (four times maintenance). Digestibilities of DM for the control, distillers grains, and soyhull diets, respectively, were: for dry cows, 84.1, 66.6, and 78.8%; for medium producers, 76.6, 53.8, and 74.2%; and for high producers, 60.5, 44.3, and 62.8%. At ad libitum intake, the DM, NDF, ADF, and CP digestibilities were lower for control than for the soyhulls diet. Discounts per unit of maintenance of 9.3, 11.2, and 6.8% were obtained for the control, distillers grains, and soyhull diets. These results confirm the generally accepted concept of energy discounts for grain-soybean meal diets, but discounts were higher than reported previously. Compared with the control diet soyhulls appears to lower, and distillers grains increase, the discount. © 1989, American Dairy Science Association. All rights reserved.