The effect of porcine somatotropin (pST) and gender on production parameters and tissue yield of pigs slaughtered at 135 kg live weight

Eighteen F1 crossbred (commercial-type terminal crosses) pigs (boars, barrows and gilts) with an initial weight of 27.2 ± 2 kg were used to investigate the effect of porcine somatotropin (pST) administered for six weeks prior to slaughter on production parameters and tissue yield in the South African scenario. Pigs were grown to 135 kg live weight, which is heavier than the average weight at slaughter in South Africa of 80 - 100 kg. Porcine somatotropin had no significant effect on average daily gain or feed intake. However, pST administration caused a significant increase in feed conversion ratio (kg feed/kg gain) of treated boars, indicating that boars converted their feed less efficiently when treated with pST. This contradicts most of the findings in the literature. The effect of pST on the different carcass cuts was not significant, except for the percentage loin back, which was higher for pST-treated animals and percentage middle back of boars and barrows, which was slightly higher. No significant pST effects were found for live weight, carcass weight, % bone, % fat or % lean meat, but a significant increase in percentage skin was found.