Maggiolino Aristide, Forte Lucrezia, Aloia Alessandra, Bernabucci Umberto, Trevisi Erminio, Lecchi Cristina, Ceciliani Fabrizio, Dahl Geoffrey E, De Palo Pasquale
Department of Veterinary Medicine, University of Bari A. Moro, Valenzano, Italy.
Department of Agriculture and Forest Sciences (DAFNE), University of Tuscia, Viterbo, Italy.
Front Vet Sci. 2025 Apr 28;12:1582884. doi: 10.3389/fvets.2025.1582884. eCollection 2025.
Dairy cows are highly susceptible to heat stress, raising concerns about animal welfare, production efficiency, and economic losses. Previous studies suggest that Holstein and Brown Swiss breeds exhibit different levels of thermal tolerance, but their short-term adaptive responses require further investigation.
This study aimed to evaluate breed-specific physiological and productive responses to a 4-day natural heat wave in 40 lactating cows (20 Holstein, 20 Brown Swiss) from the same commercial dairy farm, homogeneous for days in milk, body condition score, parity, and energy-corrected milk yield. Before the heat wave, cows experienced at least 48 h in thermoneutral conditions. Physiological parameters were recorded three times daily (4:00 AM, 3:00 PM, and 8:00 PM). Blood samples were collected before the heat wave (D1, 4:00 AM, thermoneutral conditions) and at the warmest moment of the fourth day (D4, 3:00 PM, heat stress conditions).
The heat wave negatively impacted physiological parameters in both breeds. Rectal temperature increased daily from 4:00 AM to 3:00 PM ( < 0.01), with Holstein cows showing consistently higher values than Brown Swiss ( < 0.01). Respiration rate reached its lowest point at 4:00 AM each day ( < 0.01) but remained elevated at 8:00 PM, despite decreasing THI, indicating accumulated heat load. While both breeds followed a similar trend, Holsteins exhibited a greater capacity for overnight recovery compared to Brown Swiss. Regarding productivity, Brown Swiss cows maintained stable milk yield (MY) from D1 to D4, whereas Holsteins showed a progressive MY decline throughout the heat wave ( < 0.01). Most blood parameters showed no significant breed differences ( > 0.05), but heat shock protein 70, a key regulator of thermal adaptation, exhibited an increasing trend in both breeds ( < 0.01), appearing earlier than other physiological indicators of heat stress.
This study, conducted under identical conditions, highlights distinct breed-specific responses to short-term heat stress. The findings suggest that Brown Swiss cows may be more resilient to heat stress in terms of productivity, while Holsteins show better nighttime recovery. Further research should explore additional physiological and molecular markers to better characterize breed differences and improve heat stress mitigation strategies in dairy farming.
奶牛极易受到热应激的影响，这引发了人们对动物福利、生产效率和经济损失的担忧。先前的研究表明，荷斯坦奶牛和瑞士褐牛品种表现出不同程度的耐热性，但其短期适应性反应仍需进一步研究。
本研究旨在评估来自同一商业奶牛场的40头泌乳奶牛（20头荷斯坦奶牛、20头瑞士褐牛）对为期4天的自然热浪的品种特异性生理和生产反应，这些奶牛在产奶天数、体况评分、胎次和能量校正奶产量方面保持一致。在热浪来临前，奶牛在热中性条件下经历了至少48小时。每天记录三次生理参数（凌晨4点、下午3点和晚上8点）。在热浪来临前（第1天，凌晨4点，热中性条件）和第四天最热时刻（第4天，下午3点，热应激条件）采集血样。
热浪对两个品种的生理参数均产生了负面影响。直肠温度从凌晨4点到下午3点每天都在升高（<0.01），荷斯坦奶牛的直肠温度始终高于瑞士褐牛（<0.01）。呼吸频率每天凌晨4点达到最低点（<0.01），但尽管温湿度指数下降，晚上8点时仍保持在较高水平，这表明存在累积的热负荷。虽然两个品种都呈现出相似的趋势，但与瑞士褐牛相比，荷斯坦奶牛夜间恢复能力更强。在生产力方面，瑞士褐牛从第1天到第4天的产奶量保持稳定，而荷斯坦奶牛在整个热浪期间产奶量逐渐下降（<0.01）。大多数血液参数在品种间无显著差异（>0.05），但热休克蛋白70作为热适应的关键调节因子，在两个品种中均呈上升趋势（<0.01），且比其他热应激生理指标出现得更早。
本研究在相同条件下进行，突出了不同品种对短期热应激的独特反应。研究结果表明，瑞士褐牛在生产力方面可能对热应激更具弹性，而荷斯坦奶牛夜间恢复能力更好。进一步的研究应探索更多的生理和分子标记，以更好地表征品种差异，并改进奶牛养殖中的热应激缓解策略。
