PSV-36 The impact of selection using residual average daily gain and marbling EPDs on growth performance and carcass traits in angus steers

Abstract

Abstract This study compared growth performance, feed efficiency, body composition, and carcass characteristics in Angus steers (n = 321) from bulls divergently selected for feed efficiency and marbling. Angus sires were selected based on high (10th percentile or better) and low (85th percentile or worse) residual ADG (RADG) EPD as well as high (5th percentile or better) and average (near 50th percentile) marbling (MARB) EPD. These criteria resulted in a 2x2 factorial design with four breeding lines: high RADG/high MARB, high RADG/average MARB, low RADG/high MARB, low RADG/average MARB. Data were analyzed using MIXED procedures of SAS with RADG and MARB as main effects. Ultrasound and carcass data revealed no differences (P ≥ 0.12) in 12th rib backfat thickness from weaning through slaughter for the RADG EPD groups. At the beginning and the end of the feeding trial, the high RADG (P ≤ 0.02) group had larger ultrasound ribeye area than the low RADG group. During the feedlot trial and through slaughter, BW was heavier (P ≤ 0.006) for the high versus low RADG steers but did not differ (P ≥ 0.44) across MARB EPD. Feed efficiency measures did not differ (P ≥ 0.32) across RADG or MARB groups apart from the tendency (P = 0.08) for residual feed intake to be lower in the high versus low RADG steers. Marbling scores differed (P ≤ 0.04) across RADG and MARB groups with the low RADG steers and the high MARB steers having improved marbling. The quality grade distribution across MARB EPD revealed that the average MARB steers graded 73% Choice and 25% Prime while the high MARB steers graded 56% and 42%, respectively. Slice shear force did not differ (P ≥ 0.32) across RADG or MARB EPD. These results suggest that selection using RADG EPD has negligible impacts on meat quality; moreover, they show that progress in selection for efficiency can be accomplished while advancing carcass quality and value.