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

The effects of three feed withdrawal treatments (unfasted, 15 h overnight f ast at the abattoir, 15 h overnight fast at the piggery) and three addition al abattoir lairage times (0-1, 2-3 or 4-5 h) on pig carcass and non-carcas s body component yields and on muscle quality characteristics were evaluate d. Liveweight yield was lower (P < 0.05) for pigs fasted in the abattoir (b y 17 g kg(-1)) and the piggery (by 22 g kg(-1)) than for unfasted pigs give n a 2-5 h abattoir lairage. Of this decrease, 40-50% was attributed to a lo wer carcass yield, while the remainder was attributed to a decrease in yiel d of noncarcass components, especially the gastrointestinal tract. Feed wit hdrawal decreased (P < 0.05) the amount of distension of the intestinal tra ct, and increased (P < 0.05) the amount of carcass skin damage due to fight ing. It had no effect (P > 0.05) on carcass lean yield, amount of shrink du ring the chilling process, yield of wholesale cuts, yields of dissected lea n, fat and bone in the wholesale cuts, or moisture, fat and protein levels in the longissimus thoracis (LT) muscle. The overnight fast had little impa ct on LT muscle quality with the exception of slight darkening of the colou r of muscles of pigs from which feed was withdrawn at the pig gery. Feed wi thdrawal has the potential to reduce the problem of disposal of gut content s and the risk of carcass contamination as a result of nicking the gastroin testinal tract, and to slightly darken muscle tissue without affecting othe r meat quality traits. These benefits must be balanced against a decreased carcass yield and an increase in skin damage due to fighting.