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<p>This study evaluated the effects of thermal stress, season, and genetic composition on metabolic and reproductive parameters in crossbred dairy cows. A total of 960 lactating cows (Holstein Friesian × Desi), representing two exotic blood levels (50% and 75%), were monitored across four seasons. All these cows (<i>n</i> = 960) were inseminated at estrus using semen from a single bull, and reproductive responses were assessed alongside blood metabolites and hormone profiles. Blood samples were analyzed for glucose, protein, triglycerides (TG), cortisol, luteinizing hormone (LH), and progesterone (P₄). Temperature-humidity index (THI) was calculated to classify stress zones. Thermal stress significantly decreased serum glucose and TG levels, while protein and cortisol levels increased. Seasonal variation followed a similar pattern, with winter being metabolically favorable and summer showing elevated stress markers. LH concentrations declined under severe stress, particularly in cows with 75% exotic blood, while P₄ levels increased marginally. Fertility, as measured by pregnancy rate, was negatively affected by rising THI but improved with better body condition scores (BCS), highlighting the resilience of cows with BCS ≥ 3. Overall, heat stress disrupted endocrine and metabolic balance, especially in high-exotic-cross cows. The findings emphasize the importance of breed selection, seasonal breeding, and nutritional strategies to improve reproductive efficiency under subtropical climatic conditions.</p>

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Impact of genetic composition on cows’ metabolic and fertility responses to thermal stress

  • 期刊论文

  • 发表日期：

    2026年4月14日

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  • Ihsan Ullah,
  • Muhammad Subhan Qureshi,
  • Raed M. Al-Atiyat,
  • Shah Murad Khan,
  • Ihtesham Ul Haq,
  • Shabana Naz,
  • Rifat Ullah Khan,
  • Babar Maqbool,
  • Marco Ragni,
  • Ibrahim A. Alhidary

摘要

This study evaluated the effects of thermal stress, season, and genetic composition on metabolic and reproductive parameters in crossbred dairy cows. A total of 960 lactating cows (Holstein Friesian × Desi), representing two exotic blood levels (50% and 75%), were monitored across four seasons. All these cows (n = 960) were inseminated at estrus using semen from a single bull, and reproductive responses were assessed alongside blood metabolites and hormone profiles. Blood samples were analyzed for glucose, protein, triglycerides (TG), cortisol, luteinizing hormone (LH), and progesterone (P₄). Temperature-humidity index (THI) was calculated to classify stress zones. Thermal stress significantly decreased serum glucose and TG levels, while protein and cortisol levels increased. Seasonal variation followed a similar pattern, with winter being metabolically favorable and summer showing elevated stress markers. LH concentrations declined under severe stress, particularly in cows with 75% exotic blood, while P₄ levels increased marginally. Fertility, as measured by pregnancy rate, was negatively affected by rising THI but improved with better body condition scores (BCS), highlighting the resilience of cows with BCS ≥ 3. Overall, heat stress disrupted endocrine and metabolic balance, especially in high-exotic-cross cows. The findings emphasize the importance of breed selection, seasonal breeding, and nutritional strategies to improve reproductive efficiency under subtropical climatic conditions.