USE OF EXPECTED PROGENY DIFFERENCES FOR MARBLING IN BEEF .1. PRODUCTION TRAITS

Six Angus bulls with HIGH (>.4) and six bulls with LOW (<-.16) expecte d progeny differences (EPD) for marbling were used to evaluate the imp act of marbling on progeny production and carcass traits. Bulls were r andomly bred to MARC II (1/4 Hereford, 1/4 Simmental, 1/4 Angus, 1/4 G elbvieh) composite cows in each of 2 yr to calve in the spring. At wea ning, steers and heifers were separated and managed in different produ ction systems. Steers (n = 131) were fed a growing diet (1.1 Meal of N E(g)/kg) for 48 d followed by adaptation to a 93% concentrate finishin g diet. Heifers (n = 125) were fed a growing diet (.79 Mcal of NE(g)/k g) for 191 d followed by adaptation to the same 93% concentrate diet. Steers and heifers from each treatment were slaughtered at two times s paced about 60 d apart within both years. Marbling EPD class had no ef fect on fat thickness, USDA yield grade, carcass weight, finishing dai ly gain, finishing DMI, or finishing efficiency (P >.18). More (P <.05 ) carcasses of calves from sires with HIGH EPD for marbling graded USD A Choice than from LOW EPD sires, 74% vs 47%, respectively. Angus sire s can be selected to produce progeny that have increased ability to gr ade Choice without increasing yield grade or decreasing animal growth or feed efficiency.