Comparison of Forage and Concentrate Digestibility in Sheep and Cattle

The objectives were to determine the efficacy of sheep as a digestibility model for cattle using two diets, forage or concentrate-based, with modern genetics and management. Diets, with ingredients of grass hay, corn grain, soybean meal, and urea, were formulated to contain either 80% forage or 80% concentrate on DM basis to compare digestibility between wethers and steers. Twelve Suffolk wethers were blocked into 2 blocks with 6 wethers in each block. Wethers within a block were divided into 2 groups (A and B) with 3 wethers in each group. Wethers in group A were fed 80% forage diet while group B wethers were on 80% concentrate diet. Six Angus steers were also blocked in 2 groups (A and B) with 3 steers in each group. In period 1, steers from group A were fed 80% forage diet while group B steers were on 80% concentrate diet. Steers were fed in a switchback design. Wethers and steers were fed for ad libitum intake. After 3 weeks of adaptation on diets, feed intake, refusals, and feces were collected and measured. Feed and fecal DM, OM, NDF, and ADF were analyzed. Refusals were analyzed for DM. Data were analyzed using Proc Mixed in SAS with diet, species, and block as fixed effects and then with Proc Corr in SAS. There was an interaction (P0.45; DM r=0.32, P>0.36). There were no interactions (P≥0.83) for fiber digestibility; NDF and ADF digestibility were greater (P