| dc.description.abstract |
Groups of six crossbred lambs, three wethers and three ewes, about 22 kg liveweight (LW), were injected subcutaneously with 0, 50, 150 and 250 pg (kg LW) d a y 1 of recombinant DNA-derived bovine growth hormone (rebGH) for 60 days. From blood sampled twice weekly 4.5 h after injection, the mean plasma concentrations of growth hormone (GH) (P<0.01) and insulin (P<0.05) were significantly increased. The mean concentrations of GH were 2.9, 7.1, 9.4 and 8.8 8g/l, while insulin concentrations were 24.2, 29.5, 46.8 and 68.2 mU/l for the respective treatments. Maximum concentrations of plasma GH were recorded about 3 h after injection. Rates of liveweight gain were 180, 217,238 and 261 g/day (P<0.001), fccd conversion ratios were 5.71,4.97,4.66 and 4.05 g feed/g gain ( P < 0.001), and warm carcase weights were 14.4, 16.4, 16.6 and 16.8 kg (P < 0.0 1) for the respective treatments. The linear change in warm carcase weights became a quadratic response (P<0.05) when adjusted to an empty body weight (EBW) of 28.8 kg. Wool growth was not affcctcd by treatments. Of the non-carcase components, major organs including the head (P<0.01), feet (P<0.05), heart (P<0.05), liver and gallbladder (P < 0.05), reticula-rumen (P < 0.05), omasum (P<0.05) and blood (P<0.01) showed linear increases in weight with increasing dosage of rebGH, but no significant differences when data were adjusted to a standard EBW. The chemical composition of the carcase showed that crude protein increased linearly (P<0.001) with increasing doses of rebGH. When adjusted to 28.8 kg empty body weight, there was 16.0�_/o more carcase protein (P<0.01) with 250 than with 0 8g (kg LW)-1 day-1 of rebGH. |
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