15 Enhanced core body temperature regulation reveals improved reproductive performance in the heat-tolerant Holstein cows

Z. Luo; J. Wang; Y. Xiao; Q. Zhang; S. Hou; Q. Liu; Y. Zhang; A. Jin; W. Liu; C. Yang; Y. Li; Z. Ju; Y. Gao; J. Huang

doi:10.1071/RDv36n2Ab15

RESEARCH ARTICLE

15 Enhanced core body temperature regulation reveals improved reproductive performance in the heat-tolerant Holstein cows

Z. Luo ^A ^C , J. Wang ^A ^B , Y. Xiao ^A ^B , Q. Zhang ^A ^B , S. Hou ^A ^B , Q. Liu ^A ^B , Y. Zhang ^A ^B , A. Jin ^A ^B , W. Liu ^A ^B , C. Yang ^A ^B , Y. Li ^A ^B , Z. Ju ^A ^B , Y. Gao ^A ^B and J. Huang ^A ^B

+ Author Affiliations

- Author Affiliations

^A Shandong Key Laboratory of Animal Disease Control and Breeding, Shandong Academy of Agricultural Sciences, Ji’nan City, Shandong, China

^B Key Laboratory of Livestock and Poultry Multi-omics of MARA, Ji’nan City, Shandong, China

^C College of Animal Science and Technology Ningxia University, Yinchuan City, Ningxia, China

Reproduction, Fertility and Development 36(2) 157 https://doi.org/10.1071/RDv36n2Ab15

We aimed to evaluate the effects of hot environment on vaginal temperature and reproduction performance traits: days open and the first service conception rates (FSC) in Holstein cows in eastern China. The experiment was performed at a Holstein cow farm in Dezhou City, Shandong Province, China (N36.8°, E116.5°). The temperature and humidity in the barns were measured and recorded every 10 min using Eli-tech temperature and humidity data loggers. The vaginal temperature of the investigated cows was measured every 10 min for 24 h using Thermochron iButton temperature loggers (DS1922L-F5#), which were fixed in CIDRs (Zoetis) and placed in the cow’s vagina. We measured the vaginal temperature of 55 milking cows in the spring (April 2023) and 210 milking cows in the summer (July 2023). The reproductive records of the cows were retrieved from the herd management software. Data are shown as means ± standard deviation. The mean average temperature-humidity index (THI) increased significantly from 56 in April to 80 in July. Accordingly, the average and maximum 24 h vaginal temperatures of cows were both significantly increased from April to July, respectively (38.49 ± 0.11°C vs 39.09 ± 0.2°C, P < 0.0001; 39.1 ± 0.19°C vs 40 ± 0.26°C, P < 0.0001), except that the minimum temperatures were not affected by the season (38.19 ± 0.11°C vs 38.26 ± 0.21°C, P = 0.14). To identify heat-tolerant (HT) and heat-intolerant (HI) cows in summer, we sorted animals by the mean vaginal temperature from high to low and selected the top 30% as the HI group and the bottom 30% as the HT group. The average vaginal temperatures of HI and HT cows were 39.24 ± 0.22°C and 38.67 ± 0.09°C, respectively. We compared the days open of the two groups and found that the HT group had ~15 days shorter for the open period than HI group (111.2 ± 67.48 vs 126.02 ± 64.76, P < 0.05). Results also showed that the FSC was 14% higher in the HT group compared to the HI group (54% vs 40%, P = 0.0214, chi-square test). The current study suggests that although the body temperature of Holstein cows elevates as ambient temperature increases, part of them show relatively lower body temperatures and better performance in reproductivity traits. Therefore, the selection of cows with greater capacity for body temperature regulation may benefit the reproduction performance of dairy cows.