SILAGE OR LIMIT-FED GRAIN GROWING DIETS FOR STEERS .1. GROWTH AND CARCASS QUALITY

The influence of energy source (silage- [S] or grain- [G] based) on or gan growth, carcass quality, and meat acceptability independent of rat e of gain was examined. Sixty-four Angus steers were allotted to one o f the two treatments and given ad libitum access to silage or limit-fe d grain for 145 d. All steers were then given ad libitum access to a g rain diet for 45, 75, or 105 d. Eight steers from each treatment were slaughtered at the end of the growing phase and at each of the termina tion dates. The silage-based growing diet consisted (DM basis) of 55% sorghum silage (averaged 23.6% dry matter), 22% alfalfa hay, 10.8% gro und shelled corn, and 10.8% soybean meal and contained 12.8% CP. Dry m atter in the grain-based diet, composed of 76.5% ground shelled corn, 5% soybean meal, 13.6% cottonseed hulls, 3.5% molasses, and .4% salt a nd 1% limestone, contained 12.1% CP. It was limit-fed to produce rates of gain similar to the silage diet eaten ad libitum, using net energy for gain of each diet calculated from organic matter digestibility de termined in digestion trials. The finishing diet was similar to the gr ain growing diet except that alfalfa hay replaced the cottonseed hulls . No implants or ionophores were used. High silage moisture decreased ADG the first 45 d, so steers fed grain gained faster, but thereafter gains were similar. At the end of the growing phase, steers fed grain had heavier shrunk and empty body weights and larger livers. However, liver size was not different when adjusted for growing ADG. By 45 d wi th ad libitum access to the finishing diet, 75% bf the carcasses from steers fed both diets graded Choice. Steers fed silage had tougher (P < .05) steaks with less flavor intensity (P < .05) at, the end of the growing phase; these differences diminished after 75 d on feed. These results suggest that Choice beef can be produced in only 45 d in the f eedlot, but tenderness and flavor among Choice carcasses remained infe rior for steers fed silage for at least 75 d on a high-grain diet.