Impact of Heat Stress on Milk Production and Reproductive Performance in Dairy Cattle

Muhammad Jawad Khan; . Shakirullah; Irtaza Hussain; Imtiaz Ahmed Cheema; Mian Muhammad Salman; Bilal Ahmad; Atta Ur Rahman; Shahzada Khurram Adrian Shah; Sundas Qamar; Gohar khadim

doi:10.54112/bcsrj.v7i5.2307

Authors

Muhammad Jawad Khan Livestock and Dairy Development Board, Islamabad, Pakistan
. Shakirullah Faculty of Veterinary and Animal Sciences, Gomal University, Dera Ismail Khan, KPK, Pakistan
Irtaza Hussain Department of Pathobiology, Faculty of Veterinary Sciences, Bahauddin Zakariya University, Multan, Punjab, Pakistan
Imtiaz Ahmed Cheema Livestock & Dairy Development Department, Baluchistan, Quetta, Baluchistan, Pakistan
Mian Muhammad Salman Department of Pathobiology, College of Veterinary Sciences and Animal Husbandry, Abdul Wali Khan University, Mardan, Khyber Pakhtunkhwa, Pakistan
Bilal Ahmad Department of Clinical Medicine and Surgery, University of Agriculture, Faisalabad, Punjab, Pakistan
Atta Ur Rahman College of Veterinary Sciences and Animal Husbandry, Abdul Wali Khan University, Mardan, Khyber Pakhtunkhwa, Pakistan
Shahzada Khurram Adrian Shah Department of Clinical Studies, Faculty of Veterinary Sciences, The University of Veterinary and Animal Sciences (UVAS), Swat, Khyber Pakhtunkhwa, Pakistan
Sundas Qamar Research Centre for Conservation for Indigenous Breeds (RCCIB), Jhang, Punjab, Pakistan
Gohar khadim Faculty of Biological Sciences, Department of Microbiology, Quaid-i-Azam University, Islamabad, Pakistan

DOI:

https://doi.org/10.54112/bcsrj.v7i5.2307

Keywords:

Cattle; Heat Stress Disorders; Humidity; Lactation; Milk; Reproduction; Temperature

Abstract

Heat stress is a major environmental constraint affecting dairy cattle productivity, particularly in regions with high ambient temperature and humidity. Elevated Temperature-Humidity Index (THI) may reduce milk production and impair reproductive efficiency.Objective: To determine the effect of heat stress on milk yield and reproductive performance of lactating dairy cows during summer using the Temperature-Humidity Index. Methods: This observational study was conducted during the summer season among 120 lactating dairy cows in a dairy farm setting. Cows were categorized into four groups according to THI: normal, mild, moderate, and severe heat stress. Productive parameters included milk yield, milk fat percentage, and milk protein percentage, while reproductive parameters included estrus expression, days to first estrus, conception status, services per conception, and days open. Data were analyzed using SPSS. Descriptive statistics were calculated, one-way ANOVA was applied for comparison of continuous variables, chi-square test was used for categorical variables, Pearson correlation assessed the relationship between THI and outcome variables, and linear regression was performed to determine the predictive effect of THI on milk yield. Results: Increasing THI was significantly associated with reduced milk yield, milk fat percentage, and milk protein percentage (p<0.001). Reproductive performance was also adversely affected, with cows under severe heat stress showing weaker estrus expression, delayed first estrus, lower conception rate, higher number of services per conception, and prolonged days open compared with cows maintained under normal thermal conditions. Pearson correlation showed a strong negative association between THI and milk production traits, while THI was positively correlated with indicators of reproductive inefficiency. Linear regression further confirmed THI as a significant predictor of reduced milk yield. Conclusion: Heat stress significantly compromises milk production and reproductive performance in dairy cows. Regular monitoring of THI, along with heat-abatement strategies and improved environmental management, may help sustain productivity and fertility during hot and humid seasons.

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