Heat stress affects dairy cow health status through blood oxygen availability

Jia Zeng; Jie Cai; Diming Wang; Hongyun Liu; Huizeng Sun; Jianxin Liu

doi:10.1186/s40104-023-00915-3

Heat stress affects dairy cow health status through blood oxygen availability

J Anim Sci Biotechnol. 2023 Sep 2;14(1):112. doi: 10.1186/s40104-023-00915-3.

Authors

Jia Zeng^{1

2}, Jie Cai², Diming Wang², Hongyun Liu², Huizeng Sun^{1

2}, Jianxin Liu^{3

4}

Affiliations

¹ Key Laboratory of Dairy Cow Genetic Improvement and Milk Quality Research of Zhejiang Province, College of Animal Sciences, Zhejiang University, Hangzhou, China.
² Ministry of Education Key Laboratory of Molecular Animal Nutrition, Zhejiang University, Hangzhou, China.
³ Key Laboratory of Dairy Cow Genetic Improvement and Milk Quality Research of Zhejiang Province, College of Animal Sciences, Zhejiang University, Hangzhou, China. liujx@zju.edu.cn.
⁴ Ministry of Education Key Laboratory of Molecular Animal Nutrition, Zhejiang University, Hangzhou, China. liujx@zju.edu.cn.

Abstract

Background: Rises in global warming and extreme weather occurrence make the risk of heat stress (HS) induced by high ambient temperatures more likely in high-yielding dairy cows, resulting in low milk quality and yield. In animals, oxygen is involved in many physiological and metabolic processes, but the effects of HS on oxygen metabolism remain unclear. Thus, the current study aimed to investigate how oxygen metabolism plays a role in health status of dairy cows by measuring the milk yield, milk composition, and blood biochemical variables of cows under different levels of HS: none (No-HS), mild (Mild-HS), and moderate HS (Mod-HS).

Results: The HS significantly increased rectal temperature (P_treat < 0.01) and respiration rate (P_treat < 0.01). Under Mod-HS, greater Na⁺ (P < 0.05) and lower total CO₂, and pH (P < 0.05) were observed relative to those under No-HS and Mild-HS. Oxygen concentrations in both coccygeal artery and mammary vein (P_treat < 0.01) were lower under Mod-HS than under No-HS. Coccygeal vein concentrations of heat shock protein 90 (HSP90) (P < 0.05) increased during Mod-HS compared with those in cows under No-HS. Malondialdehyde increased during Mod-HS, and glutathione peroxidase (P < 0.01) increased during Mild-HS. Coccygeal vein concentrations of vascular endothelial growth factor (P < 0.01), heme oxygenase-1 (P < 0.01), and hypoxia-inducible factor 1α (P < 0.01) were greater in cows under Mod-HS than those under No-HS. Red blood cell count (P < 0.01) and hemoglobin concentration (P < 0.01) were lower in the coccygeal vein of dairy cows under Mild- and Mod-HS than those of cows under No-HS.

Conclusions: Exposure to HS negatively impacts the health status and lactation performance of dairy cows by limiting oxygen metabolism and transportation. However, the specific mechanism by which HS affects mammary function in cows remains unclear and requires further exploration.

Keywords: Dairy cow; Health status; Heat stress; Lactation performance; Oxygen metabolism.

Grants and funding

31930101/National Nature Science Foundation