Effect of Reducing Soybean Protein Solubility by Dry Heat on the Protein Utilization of Young Lambs

Abstract

Growth, digestibility and nitrogen retention trials were conducted to study the effect of dry heating soybean protein to reduce its solubility on nutrient utilization in sheep. The soybean meal was heated at 149° C. for 4 hr. in a forced-air oven, which reduced protein solubility from 72 to 35%. Lamb performance was highest when the protein level was 17%, but heating the soybean meal resulted in improved gains at the 12% protein level to a point where they were comparable to those obtained on the 17% protein level. Nitrogen retention was increased when the soybean meal was heated on the 12% protein ration. Decreasing protein solubility by heat resulted in decreased levels of isovaleric and valeric acids and increased cellulose digestion. This suggests that the rate of proteolysis was decreased in the rumen, thus resulting in a more efficient utilization of the available nitrogen.