The effect of thermal preslaughter stress on the susceptibility of broiler chickens differing with respect to growth rate, age at slaughter, blood parameters, and ascites mortality, to hemorrhages in muscles

In this study we investigated the occurrence of hemorrhages in four groups of electrically stunned broilers, differing with respect to growth rate, age at slaughter, hemodynamic parameters, and ascites mortality. In addition, the effect of three thermal preslaughter conditions on hemorrhage occurrence in thigh and breast muscles was studied. Broilers were either reared at a thermoneutral or low temperature regimen, and were either restricted in their feed consumption or consumed feed ad libitum. Prior to slaughter the broilers were exposed for 2 ± 0.5 h to either cold (4 ± 2 C, RH 100%), moderate (19 ± 2 C, RH: 70 to 80%), or warm (30 ± 2 C, RH: 60 to 70%) conditions. There was no effect of rearing group, nor was there an interaction between rearing group and preslaughter condition on hemorrhage scores in the thighs or breasts. Preslaughter conditions only affected hemorrhage scores in the left thigh. Scores were highest in broilers exposed to moderate preslaughter conditions. These data indicate that the cause of hemorrhages in muscles is multifactorial. Hemorrhage severity was not diminished in broilers retarded in growth. Pathological hemodynamic adaptations to low rearing temperatures/ leading to ascites, did not increase hemorrhage severity, neither upon exposure to moderate nor to cold or warm preslaughter conditions.