Net Energy of Corn and Bird Resistant Grain Sorghum Rations for Steers when Fed as Grain or Silage

Abstract

Two separate feedlot trials were conducted to compare the feeding value of corn and bird resistant grain sorghum fed as grain or silage to steers. Steers fed corn rations had a higher daily gain and feed efficiency than those fed either of the bird resistant sorghum rations. Rolling of the bird resistant sorghum silage resulted in a highly significant (P<.01) increase in daily gains. Steers fed rolled bird resistant sorghum silage gained 29% faster than those fed unrolled bird resistant sorghum silage and feed efficiency was improved by 19%. When determined by the comparative slaughter technique, the corn silage ration had the highest NE_m+p̄ (1.40 megcal per kg D.M.) followed by the corn grain, (1.29 megcal per kg), bird resistant sorghum silage, (0.95 megcal per kg) and bird resistant sorghum grain (0.94 megcal per kg) rations. Since more dry matter was consumed from the corn grain ration, the daily intake of NE_m+p̄ was higher. The daily intake of NE_m+p̄ from the bird resistant sorghum silage ration was considerably lower than that of the other three rations. In a single reversal digestion trial corn silage had significantly (P<.05) higher digestibilities of dry matter, cellulose and protein than the mature bird resistant sorghum silage. Digestion coefficients for immature bird resistant sorghum silage were not significantly different from the other two silages, indicating that it was intermediate in digestibility between corn silage and mature bird resistant sorghum silage. Whole grains were separated from feed and feces samples of both bird resistant sorghum silages. From these data it was estimated that the steers fed immature bird resistant sorghum silage digested 22% more of the grain dry matter and 16% more of the stover dry matter than those fed mature bird resistant sorghum silage.