title: Constant heat stress reduces skeletal muscle protein deposition in broilers.
abstract: BACKGROUND
  This experiment was conducted to evaluate the effects of constant heat stress on growth performance and protein metabolism in skeletal muscle of Arbor Acres broilers.
  
  
  RESULTS
  Two hundred and seventy 21-day-old Arbor Acres broilers with similar body weight (1298 ± 28 g) were selected for a 3-week trial (29-49 days of age). The broilers were randomly assigned to three groups including the control group, constant heat stress group and pair-fed group. Up-regulation of the rectal temperature and the mRNA expression of heat shock protein 70 in liver indicate that the model for constant heat stress was success. The average daily gain, feed conversion ratio, breast and thigh muscle weight, percentage of breast muscle, crude protein content in breast and thigh muscle in constant heat stress group were significantly lower than in control group and pair-fed group. Serum uric acid content and the glutamic-oxaloacetic transaminase activity were significantly higher, while protein content and glutamic-pyruvate transaminase activity were significantly lower in liver of heat stress group than of the control and pair-fed groups. The expression of insulin-like growth factor 1, phosphatidylinositol 3-kinase and p70S6 kinase associated with protein synthesis were lower in breast muscle but higher in thigh muscle in heat stress group compared to the control or fed-pair groups. In thigh muscles, the expression of muscle ring-finger protein-1 and MAFbx associated with protein degradation were higher in the heat stress group than in the control and pair-fed groups.
  
  
  CONCLUSIONS
  Poor performance of the birds under heat stress may be due to lower synthesis and increased degradation of proteins.
authors.affiliation: College of Animal Science of South China Agricultural University, Guangzhou, 510642, China.
authors.forename: Jianjun
authors.initials: J
authors.lastname: Zuo
authors.forename: Mei
authors.initials: M
authors.lastname: Xu
authors.forename: Yusuf Auwalu
authors.initials: YA
authors.lastname: Abdullahi
authors.forename: Limei
authors.initials: L
authors.lastname: Ma
authors.forename: Zhongyue
authors.initials: Z
authors.lastname: Zhang
authors.forename: Dingyuan
authors.initials: D
authors.lastname: Feng
mesh_terms: D000818:Animals; D002645:Chickens / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D006358:Hot Temperature; D008099:Liver / Q000378:metabolism; D008460:Meat / Q000032:analysis*; D023421:Models, Animal; D009124:Muscle Proteins / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism*; D059748:Proteolysis; D012333:RNA, Messenger / Q000378:metabolism; D011897:Random Allocation; D013312:Stress, Physiological; D014527:Uric Acid / Q000097:blood
chemical_list: D018840:HSP70 Heat-Shock Proteins; D009124:Muscle Proteins; D012333:RNA, Messenger; D014527:Uric Acid
keywords: broilers; heat stress; muscle; protein