A growth and economic comparison of two crosses of pigs when fed ad libitum and to a scale and slaughtered at two weights

Abstract

SUMMARYWeaner Hampshire × Landrace × Large White (Hampshire cross) and Landrace × Landrace × Large White (Landrace cross) pigs were given combinations of three diets differing in crude protein content (high: H, low: Land very low: vl). Hampshire cross pigs at 90 kg, both under ad libitum and restricted feeding had greater rates of gain and eye muscle measurements and shorter carcasses than Landrace cross pigs, but were fatter after ad libitum feeding and more efficient food converters after restricted feeding. The HLL treatment led to improved gain and food conversion compared to the LLH or LLL treatment, whereas the LLH treatment led to larger eye muscle measurements. The LvlH treatment led to greater efficiency and eye-muscle area than treatment Lvlvl at 114 kg. An economic analysis was carried out to assess the relative profitability of slaughtering at a range of live weights. Curves were fitted to the data on food intake and live weight. Values were assumed for major costs, and a seven-day interval was allowed between batches of pigs. The calculations indicated that the H diet led to a slight increase in monetary return per pig per day when it was given in the post-weaning period to pigs fed to a scale. Although the Hampshire cross pigs showed a response to the H diet in the finishing period when slaughtered either at 90 or 114 kg, their calculated return was not increased. Ad libitum feeding led to a greater return for heavy but not, on average, for bacon pigs. Maximum return occurred at slaughter between 70 and 115 kg live weight and was only margin-ally greater for restricted baconers at 90 kg than for ad libitum heavy pigs at 110–115 kg. However, return as a percentage of working plus fixed capital was greater for baconers, but the ratio rose throughout the range of hypothetical slaughter weights in both groups. In-clusion of the cost of borrowing money had a negligible effect on the slaughter weight for maximum return with pigs managed in batches.