Effects of acute cold and heat stress on carcass traits blood indices and thyroid hormones in broiler chicken subjected to various pre-slaughter feed withdrawal periods

This study was carried out to investigate the effects of pre-slaughter feed withdrawal (0, 2, 4, 6, 8 h) and thermal treatments (-4 to -6, 22 and 38 to 40 ºC) on carcass features as well as certain blood parameters using 450 male broiler chickens during days 35 to 42 of age. Effects of the 15 experimental treatments evaluated in a 3×5 factorial fashion in 3 replicates of 10 birds each in a completely randomized design. Water uptake significantly reduced when birds subjected to eight hours of pre-slaughter feed withdrawal (P<0.05). Heat stress before slaughter increased weight loss and decreased thigh meat pH at 24 h postmortem compared with the birds kept in normal ambient temperature (P<0.05). Cold and heat treatments resulted in significant decrease and increase, respectively, in the rectal temperature of the birds (P<0.05). Blood potassium concentration decreased in the birds subjected to 8 h pre-slaughter feed removal (P<0.05). Acute heat exposure during pre-slaughter period significantly decreased blood concentration of phosphorus compared with the birds kept in normal ambient temperature (P<0.05). It was concluded that pre-slaughter starvation up to six hours exert no significant effect on water uptake and other variables concerned in broiler carcass. Exposure to a high ambient temperature imposes a greater negative impact than cold stress on pre-slaughter feed deprived broiler chickens.