title: Predicted optimum ambient temperatures for broiler chickens to dissipate metabolic heat do not affect performance or improve breast muscle quality.
abstract: An experiment was conducted to test the hypothesis that muscle damage in fast-growing broiler chickens is associated with an ambient temperature that does not permit the birds to lose metabolic heat resulting in physiological heat stress and a reduction in meat quality. The experiment was performed in 4 climate chambers and was repeated in 2 trials using a total of 200 male broiler chickens. Two treatments compared the recommended temperature profile and a cool regimen. The cool regimen was defined by a theoretical model that determined the environmental temperature that would enable heat generated by the bird to be lost to the environment. There were no differences in growth rate or feed intake between the two treatments. Breast muscles from birds on the recommended temperature regimen were lighter, less red and more yellow than those from the cool temperature regimen. There were no differences in moisture loss or shear strength but stiffness was greater in breast muscle from birds housed in the cool compared to the recommended regimen. Histopathological changes in the breast muscle were similar in both treatments and were characterised by mild to severe myofibre degeneration and necrosis with regeneration, fibrosis and adipocyte infiltration. There was no difference in plasma creatine kinase activity, a measure of muscle cell damage, between the two treatments consistent with the absence of differences in muscle pathology. It was concluded that breast muscle damage in fast-growing broiler chickens was not the result of an inability to lose metabolic heat at recommended ambient temperatures. The results suggest that muscle cell damage and breast meat quality concerns in modern broiler chickens are related to genetic selection for muscle yields and that genetic selection to address breast muscle integrity in a balanced breeding programme is imperative.
authors.affiliation: b University of Veterinary and Animal Sciences , Lahore , Pakistan.
authors.forename: I
authors.initials: I
authors.lastname: Zahoor
authors.affiliation: c SRUC, Easter Bush , Midlothian , EH25 9RG , UK.
authors.forename: M A
authors.initials: MA
authors.lastname: Mitchell
authors.affiliation: c SRUC, Easter Bush , Midlothian , EH25 9RG , UK.
authors.forename: S
authors.initials: S
authors.lastname: Hall
authors.affiliation: a Roslin Institute and R(D)SVS , University of Edinburgh, Easter Bush , Midlothian , EH25 9RG , UK.
authors.forename: P M
authors.initials: PM
authors.lastname: Beard
authors.affiliation: d University of KwaZulu-Natal , Private Bag X01, Scottsville , 3209 , South Africa.
authors.forename: R M
authors.initials: RM
authors.lastname: Gous
authors.affiliation: e Department of Animal Breeding and Genetics , Swedish University of Agricultural Sciences , 750 07 Uppsala , Sweden.
authors.forename: D J
authors.initials: DJ
authors.lastname: De Koning
authors.affiliation: a Roslin Institute and R(D)SVS , University of Edinburgh, Easter Bush , Midlothian , EH25 9RG , UK.
authors.forename: P M
authors.initials: PM
authors.lastname: Hocking
mesh_terms: D000822:Animal Husbandry / Q000379:methods*; D000818:Animals; D002645:Chickens / Q000235:genetics / Q000502:physiology*; D018869:Heat-Shock Response; D006358:Hot Temperature / Q000009:adverse effects*; D008297:Male; D008460:Meat / Q000032:analysis*; D010369:Pectoralis Muscles / Q000473:pathology / Q000502:physiology*; D011897:Random Allocation