PSI-5 Relationships of Feed Efficiency and Growth Estimated Breeding Values in Range Sheep

Abstract United States sheep producers have selected range for larger post-weaning weights through estimated breeding values (EBVs) the past forty years. This has led to perceiving more feed being required than historical averages. Therefore, objective of this study was quantify relationship between lamb growth values, intake, and efficiency. Eighty ewe lambs (40 Targhee 40 Rambouillet) were weaned at four months age put onto a GrowsafeTM feeding system 42-day trial with 14-day adaption period. Ewe weighed weekly beginning end trial. Body weights, average daily gain (ADG), intake measurements used calculate Residual Feed Intake (RFI). The lambs’ weight EBV associated mid-trial metabolic body weight, RFI. These experimental procedures repeated in second when same ewes yearlings maintenance. While EBVs predictive dry matter (P < 0.05), there no RFI > association constant across both trials. A ewe’s also trials 0.05). suggests that while selection higher animals may increase producers’ usage due size, efficiency is not EBV. To investigate if from stage are maintenance requirements, we further compared RFI, ADG, DMI two Growth found be caution should utilizing phase as an indicator Alternatively, Ewes’ first Mid-trial positively Thus, differences likely driving seen intake. Overall, our results suggest producer’s towards post weaning increasing increased size but negatively affecting overall