title: Blood amino acids profile responding to heat stress in dairy cows.
abstract: OBJECTIVE
  The objective of this experiment was to investigate the effects of heat stress on milk protein and blood amino acid profile in dairy cows.
  
  
  METHODS
  Twelve dairy cows with the similar parity, days in milk and milk yield were randomly divided into two groups with six cows raised in summer and others in autumn, respectively. Constant managerial conditions and diets were maintained during the experiment. Measurements and samples for heat stress and no heat stress were obtained according to the physical alterations of the temperature-humidity index.
  
  
  RESULTS
  Results showed that heat stress significantly reduced the milk protein content (p<0.05). Heat stress tended to decrease milk yield (p = 0.09). Furthermore, heat stress decreased dry matter intake, the concentration of blood glucose and insulin, and glutathione peroxidase activity, while increased levels of non-esterified fatty acid and malondialdehyde (p<0.05). Additionally, the concentrations of blood Thr involved in immune response were increased under heat stress (p<0.05). The concentration of blood Ala, Glu, Asp, and Gly, associated with gluconeogenesis, were also increased under heat stress (p<0.05). However, the concentration of blood Lys that promotes milk protein synthesis was decreased under heat stress (p<0.05).
  
  
  CONCLUSIONS
  In conclusion, this study revealed that more amino acids were required for maintenance but not for milk protein synthesis under heat stress, and the decreased availability of amino acids for milk protein synthesis may be attributed to competition of immune response and gluconeogenesis.
authors.affiliation: College of Animal Science and Technology, Hunan Agricultural University, Changsha 410128, China.|State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
authors.forename: Jiang
authors.initials: J
authors.lastname: Guo
authors.affiliation: State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
authors.forename: Shengtao
authors.initials: S
authors.lastname: Gao
authors.affiliation: State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
authors.forename: Suyu
authors.initials: S
authors.lastname: Quan
authors.affiliation: State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
authors.forename: Yangdong
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: College of Animal Science and Technology, Hunan Agricultural University, Changsha 410128, China.|State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China.|Synergetic Innovation Center Of Food Safety and Nutrition, Harbin 150030, China.|World Agroforestry Centre, East and Central Asia, Beijing 100081, China.
authors.forename: Dengpan
authors.initials: D
authors.lastname: Bu
authors.affiliation: College of Animal Science and Technology, Hunan Agricultural University, Changsha 410128, China.|State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
authors.forename: Jiaqi
authors.initials: J
authors.lastname: Wang
keywords: Amino Acids; Heat Stress; Insulin; Milk Protein