Effects of implanting ram and wether lambs with zeranol at birth and weaning on palatabilty and muscle collagen characteristics

Thirty-five zeranol-implanted (I) and nonimplanted (NI) ram and wether lambs representing four treatments (implanted rams [IR], nonimplanted rams [NIR], implanted wethers [IW], and nonimplanted wethers [NIW]) were evaluated for meat palatability and muscle collagen characteristics. Rib (longissimus muscle, LM) chops from I lambs were juicier (P < 0.05) than rib chops from NI lambs. Chops from IR lambs had more (P < 0.05) detectable connective tissue and lower myofibrillar and overall tenderness scores than chops from NIR, IW, or NIW lambs. Warner-Bratzler shear (WBS) values tended to be higher (P = 0.06) for LM chops from rams than for those from wethers, but WBS values for Biceps femoris (BF) chops were similar (P > 0.05) for rams and wethers. Implanting did not affect (P > 0.05) WBS values. Rams had more (P < 0.05) LM heat-labile (soluble, SC), nonheat-labile (insoluble, IC), and total collagen (TC) and a higher (P < 0.05) percentage of SC (SC/TC) than did wethers. Soluble collagen, TC, and percentage of SC for the BF were higher (P < 0.05) and IC tended (P = 0.09) to be higher in chops from rams than in those from wethers. Implanting did not affect (P > 0.05) collagen amount or solubility. Serum nonprotein hydroxyproline (NPHP) was higher (P < 0.05) in rams than in wethers throughout the feeding period and tended (P = 0.05) to be higher at slaughter. Implanting did not affect (P > 0.05) serum NPHP. We concluded that rams synthesize and accumulate more LM muscle collagen and have higher WBS values than do wethers. However, the observed reduction in sensory panel tenderness was only for chops from implanted rams compared with chops from other treatment groups.