PSXIV-16 Performance, carcass, wholesale, and retail cuts yield of lambs reared under thermal stress in grazing conditions and slaughtered at two body weights

Abstract

Abstract Lamb production in tropical areas is conducted under heat stress in extensive grazing conditions of naturalized pastures (NP). The average daily gain (ADG) and yields of hot (HCY) and cold (CCY) carcass, wholesale cuts (WSC); neck (N), shoulder (SL), ribs 5–12 (RIB), loin (LN) and leg (LG), and detail cuts (DTC); shoulder chops (SCH), french chops (FCH), ribs (RS), back leg (BL) and shanks (SH) of 12 lambs (X = 19.4 kg) rotationally grazed (3 d occupation and 24 d resting period) for 154 or 238 d were determined. The Lambs grazed >8 h NP, grass hay and water were offered ad libitum, 150 g/d of a supplement (12% CP), and mineral blocks. Weekly weights were used to determine ADG. Lambs were slaughtered at 22 (SW1) or 35 kg (SM2) to determine HCY and CCY, and WSC and DTC yield as % of cold carcass weight. Performance data was analyzed as a randomized experimental (CRD) design over time. Carcass and cut yields data were analyzed as a CRD with 6 replicates per treatment. Lambs fed during 238-d had similar ADG than those fed 154-d (68.14 vs.47.74 g/d). SW1 and SW2 had similar percentages of HCY (35.21 vs. 38.14) and CCY (34.48 vs. 37.40). The WSC as % of cold carcass weight, N (6.43 vs. 7.06), SL (29.95 vs. 30.20), RIB (16.10 vs. 16.95), LN (10.84 vs. 11.33) and LG (36.51 vs. 34.44) were similar for SW1 and SW2. Yield of SCH and SH was lower (P < 0.05) for SW1 (15.80 and 8.11) than SW2 (23.00 and 9.11), but FCH (8.49 vs. 8.57), RS (6.89 vs. 7.00) and BL (36.52 vs 34.45) were similar. In summary, lambs slaughtered at 35 kg improved the retail cut yield, but did not influence ADG, HCY, CCY, and WCY compared to lighter lambs.