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Three summer forage finishing systems effect on lamb growth and carcass characteristics
With lambs, there is a lack of information comparing grazing alfalfa versus other summer forages, and the effects on lamb growth rate and carcass characteristics. The objective of the study was to compare three forage finishing systems on lamb growth rate and carcass characteristics. Weaned wether (n = 54) lambs blocked by body weight were used to evaluate the effect of finishing systems on rate of growth and carcass composition. Each treatment consisted of three fields of six lambs per field. The finishing systems were grazed alfalfa (ALF), grazed chicory (CHI), and grazed sorghum-sudangrass (SSG). The forages were rotational grazed. Each field was subdivided using temporary electric netting and each paddock was grazed for three days with a 28 day rest between grazing events. Forage analysis revealed ALF had lesser ADF and NDF content than CHI and SSG throughout the trial (P < 0.05) and greater CP content for all but six weeks (P < 0.05) out of the 15-week trial period. Predetermined contrasts between ALF and the other finishing systems were conducted using LSMESTIMATE in PROC MIXED. Overall ADG for ALF lambs (0.22 kg/d) was not different (P > 0.05) than SSG lambs ADG (0.20 kg/d) and trended lesser (P = 0.07) than CHI lambs ADG (0.25 kg/d). The slaughter target was predetermined to be the time when forage became limiting. The SSG lambs were slaughtered 14 d earlier than either the ALF or CHI lambs due to frost. The SSG lambs produced lighter carcasses with lesser dressing percentages than the ALF lambs (P <0.05). The ALF lambs were not different in carcass weight, loin eye area, and back fat depth from the CHI lambs (P > 0.05). There was a trend for reduced dressing percentage of the ALF lambs when compared with the CHI lambs (P = 0.08). All three forage treatments produced adequate rate of gain, but would need additional grazing time for lambs to reach adequate carcass weights.
Keywords: Lamb, grazing, carcass