PSI-3 - Allometric Growth Coefficients of Non-Carcass and Carcass Components of Serially Harvested Implanted and Non-Implanted Steers

The objective of this study was to quantify allometric growth coefficients of non-carcass and carcass components of implanted or non-implanted Charolais×Angus steers in relation to empty body weight. Steers (n = 80; initial BW 271±99 kg) were paired, randomized to harvest date (d 0-42-84-126-168-210-252-294-336-378), and CON (negative control) or REV (Revalor-XS on d 0 and 190) treatments. Weights were log transformed and consolidated to arithmetic means by treatment and harvest date. Growth coefficients were calculated using the log transformed allometric equation Y=K+aX where Y=log(part), X=log(whole), A=log(slope), and K=log(intercept), where empty body growth = 1. Coefficients by treatment were analyzed via independent t-test. Kidney (0.58 vs 0.51; P=0.06) and lungs/trachea (0.52 vs 0.46; P = 0.09) tended to grow faster for REV, and pituitary glands grew numerically faster (P = 0.82) for REV (0.71 vs 0.56). Non-carcass components with lowest growth coefficients included small intestine (0.02), large intestine (0.12), and brain/spinal cord (0.13), whereas kidney-pelvic-heart fat (2.01) accumulated quickly. Growth coefficients of primals were numerically greater for REV steers, except in the rib. All primals except round (0.81) and foreshank (0.87) exhibited coefficients greater than 1 (brisket, 1.18; chuck, 1.03; rib, 1.18; plate, 1.45; loin, 1.04; and flank, 1.47). Growth coefficients were greater (P< 0.01) for REV in two subprimals (chuck eye roll, 0.87; eye of round, 0.75), CON was greater (P < 0.01) in one subprimal (flank steak, 0.79). Pectoral meat (0.19), bottom sirloin flap (0.56), and heel meat (0.59) exhibited growth coefficients less than 1. Although not significant, total lean was deposited more quickly in REV (0.95 vs 0.88; P=0.45), whereas total fat (2.17 vs 1.98; P=0.35) and total bone (0.92 vs 0.75; P=0.29) were faster growing for CON. These data indicate fat exhibits greatest growth coefficients compared to the empty body; whereas, there were minimal differences in growth coefficients in regards to treatment.