Comparison of the effects of recombinant ovine, bovine and porcine growth hormones on growth, efficiency and carcass characteristics in lambs

Abstract

The effects of daily administration of recombinantly derived ovine growth hormone (oGH) on live weight gain, food conversion and carcass composition were studied in young lambs and the effects compared with those obtained by administration of porcine (p) or bovine (b) growth hormone (GH). Forty-eight female Coopworth lambs were reared on a complete pelleted diet and, at 16 weeks of age, were allocated to one of four treatment groups. Each lamb received a daily s.c. injection of either oGH, bGH, pGH (0.1 mg/kg bodyweight) or vehicle. Food intake was measured daily and liveweights were measured weekly for 4 weeks after which the lambs were slaughtered for measurement of carcass characteristics and organ weights. Both the oGH-and bGH-treated lambs grew faster than controls ( P<0.01) and had heavier carcasses at slaughter. No significant difference from control animals could be found for any treatment group with respect to food intake or relative appetite, but the oGH- and bGH-treated lambs had a better food conversion efficiency ( P<0.001). With the exception of reduced carcass fatness ( P<0.01) for bGH-treated lambs, no major effect of GH treatment could be detected on wool growth or carcass characteristics. Both oGH and bGH treatment resulted in increased plasma concentrations of IGF-1 ( P<0.01) compared with controls and pGH-treated lambs. All GH-treated lambs produced antibodies against the GH with which they were injected.