INFLUENCE OF SIRE GROWTH-POTENTIAL, TIME ON FEED, AND GROWING-FINISHING STRATEGY ON CHOLESTEROL AND FATTY-ACIDS OF THE GROUND CARCASS AND LONGISSIMUS MUSCLE OF BEEF STEERS

The purpose of this study was to determine how diverse beef cattle pro duction systems affect fatty acids and cholesterol of meat. Crossbred cows were bred by AI to high (H) or moderate (M) growth rate potential bulls to produce spring- or fall-born calves. Steer calves from these matings were placed on finishing diets at three ages. Spring-born ste ers were started at 6 or 18 mo of age (A6 and A18), and fall-born calv es were started at 12 mo of age (A12). Slaughter times were 0, 90, 180 , and 270 d for A6; 68, 136, and 204 d for A12; and 0, 45, 90, and 135 d for A18. Four steers of each type were slaughtered in each of 2 yr for each sire type x time on feed x slaughter group. Fatty acids and c holesterol of ground carcass and longissimus muscle (LM) were determin ed by GLC. Carcass fat increased faster in M than in H steers (P <.01) . Ground carcass cholesterol was greater for M steers (P =.06) than fo r H steers because of the greater fat content in the M ground carcass. No differences in LM cholesterol were observed for sire growth potent ial or time on feed. Fatty acid differences in ground carcass with tim e on feed were due primarily to decreases in 18:0 and increases in 18: 1. The LM saturated and monounsaturated fatty acids changed little wit h time on feed, but total saturates were greater for M steers (44.5%) than for H steers (42.8%) (P =.02). A18 steers of H sires had the grea test (P =.04) ratio of 18:0 plus unsaturates to 14:0 plus 16:0 (most h ypocholesterolemic). We conclude that cholesterol in lean muscle is no t altered by the sire growth potential x time on feed x growing-finish ing strategy imposed, and that lean beef from steers sired by H bulls and backgrounded before finishing may produce meat with the healthiest lipid composition.