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Asian-Australas J Anim Sci > Accepted Articles
DOI:    [Accepted] Published online February 23, 2017.
Blood amino acids profile responding to heat stress in dairy cows
Jiang Guo1,2, Shengtao Gao2, Suyu Quan2, Yangdong Zhang2, Dengpan Bu1,2,3,4,*, Jiaqi Wang1,2,*
1College of Animal Science and Technology, Hunan Agricultural University, changsha, China
2State Key Laboratory of Animal Nutrition, Institute of Animal Science, Chinese Academy of Agricultural Sciences, beijing, China
3Synergetic Innovation Center Of Food Safety and Nutrition, Harbin, 150030, PR China
4World Agroforestry Centre, East and Central Asia, Beijing 100081, PR China
Correspondence:  Dengpan Bu, Tel: +86-010-62813901, Fax: +86-010-62897587, Email:
Jiaqi Wang, Tel: +86-010-62813901, Fax: +86-010-62897587, Email:
Received: 2 June 2016   • Revised: 7 November 2016   • Accepted: 19 February 2017
The objective of this experiment was to investigate the effects of heat stress on milk protein and blood amino acid profile in dairy cows. 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 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). 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.
Keywords: amino acids; heat stress; insulin; milk protein
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