Effects of feed efficiency and diet on performance and carcass characteristics in growing wether lambs

Selection for feed efficiency may lead to decreased production inputs; however, associations between and other phenotypic traits of interest in sheep are not well understood. The objectives this study were 1) determine the effect diet on intake traits, 2) dietary change residual (RFI) performance 3) relationships RFI with carcass characteristics lambs fed either a concentrate or forage-based diet. In Trial 1, growing wethers (initial live weight (LW) = 51.3 ± 1.2 kg; n 78) Hampshire (n 35), Rambouillet 26), Suffolk 17) breed types blocked by initial LW randomly allocated receive (50.2% corn, 31.0% wheat middlings, 10.0% corn gluten, 2.5% cane molasses, 1.8% calcium carbonate, 1.0% dried distillers grains soluble, 0.8% sulfate, 0.2% potassium chloride, 0.4% trace minerals vitamins; 91.6% DM; 12.1% CP, 17.6% NDF, 3.0 Mcal/kg ME; 40) (67.7% alfalfa, 27.5% 1.3% salt, 0.6% 0.3% 92.3% DM, 16.2% 36.3% 2.3 38) pelleted Individual was recorded using GrowSafe System 49 days estimated each wether. Using rank efficiency, 20% most 8) least efficient from 32 total) slaughtered data recorded. Remaining forage subsequently changed 2; individual again collected 79 days, calculated MIXED procedure SAS used Trials 1 2, respectively, effects diet, class (most efficient), their interaction selected 32) 1; pen included as random effects. CORR characteristics. Overall, less variable concentrate-fed (?2 0.13 kg2) than forage-fed 0.25 kg2). Feed average daily gain (ADG) greater (P ? 0.001) compared wethers, although ratio (G:F) affected type 0.23). While rankings moderately correlated (r 0.51, r 54, respectively; P 0.02) subjected (forage concentrate), some re-ranking observed, especially low lambs. Boneless cut percentage tended 0.10) be versus wethers; there no ? 0.13) measures. Residual USDA quality grade positively correlated, but 0.17) measures observed. These suggest that ADG type, variation is associated Additionally, selection against effective improving flock genetics when efficiency. Furthermore, should unfavorably affect sheep.