Effect of pre-slaughter overnight feed withdrawal on pig carcass and muscle quality

Abstract

The effects of three feed withdrawal treatments (unfasted, 15 h overnight fast at the abattoir, 15 h overnight fast at the piggery) and three additional abattoir lairage times (0–1, 2–3 or 4–5 h) on pig carcass and non-carcass body component yields and on muscle quality characteristics were evaluated. Liveweight yield was lower (P < 0.05) for pigs fasted in the abattoir (by 17 g kg–1) and the piggery (by 22 g kg–1) than for unfasted pigs given a 2–5 h abattoir lairage. Of this decrease, 40–50% was attributed to a lower carcass yield, while the remainder was attributed to a decrease in yield of non-carcass components, especially the gastrointestinal tract. Feed withdrawal decreased (P < 0.05) the amount of distension of the intestinal tract, and increased (P < 0.05) the amount of carcass skin damage due to fighting. It had no effect (P > 0.05) on carcass lean yield, amount of shrink during the chilling process, yield of wholesale cuts, yields of dissected lean, fat and bone in the wholesale cuts, or moisture, fat and protein levels in the longissimus thoracis (LT) muscle. The overnight fast had little impact on LT muscle quality with the exception of slight darkening of the colour of muscles of pigs from which feed was withdrawn at the piggery. Feed withdrawal has the potential to reduce the problem of disposal of gut contents and the risk of carcass contamination as a result of nicking the gastrointestinal tract, and to slightly darken muscle tissue without affecting other meat quality traits. These benefits must be balanced against a decreased carcass yield and an increase in skin damage due to fighting. Key words: Feed restriction, fasting, gastrointestinal tract, gut fill, carcass yield, pork quality