CONTEXT

Climate change presents challenges for livestock productivity and animal health. Thus, management strategies to mitigate the effects of the global temperature increase on livestock production have become progressively relevant. However, the use of integrated crop-livestock-forestry systems to optimize the beef cattle thermal balance has not been examined more deeply.

OBJECTIVE

The study aimed to evaluate the microclimate in a non-shaded pasture system (NS) and in an integrated crop-livestock-forestry system (ICLF) and its influence on thermoregulatory and endocrine responses of zebu and composite bulls, during different climatic seasons.

METHODS

The experiment was carried out in a tropical region, São Carlos-SP, Brazil (21°57′42″S, 47°50′28″W). Nelore (Bos indicus) and Canchim (5/8 Bos taurus x 3/8 Bos indicus) bulls were equally allocated in a non-shaded system (NS; n = 32) or in an integrated crop-livestock-forestry system (ICLF; n = 32). The animals were monthly evaluated and the data were analyzed using a GLM Model. Means were compared using Tukey test (P < 0.05).

RESULTS AND CONCLUSIONS

The ICLF system reduced the air temperature (−0.6 °C; P = 0.0010), the Black Globe Temperature and Humidity Index-BGHI (−3.8; P < 0.0001), and the Radiant Thermal Load (−104 W/m²; P < 0.0001) compared to the NS system. The infrared thermograms of NS bulls were characterized by higher temperatures on the surface of the back and in the trunk, during Autumn and Winter (P < 0.05). In addition, NS bulls presented higher respiratory rate (RR: 35.85 ± 0.88 vs 31.97 ± 0.88 breaths/min; P = 0.0210) and internal body temperature (BT: 39.54 ± 0.05 vs 39.35 ± 0.05 °C; P = 0.0057) during Autumn. There was a significant reduction in cortisol concentration (−12.13 ng/mL; P < 0.05) in both systems throughout the experiment. Nelore bulls had lower RR and BT, lower mean concentration of cortisol, and higher secretion of triiodothyronine than Canchim bulls. The ICLF system was effective in mitigating the microclimate of pastures due to the action of natural shading, providing greater thermal comfort, especially for composite animals, and favored the maintenance of homeothermy in the bulls.

SIGNIFICANCE

This thesis has provided a deeper insight into the physiological mechanisms involved in the thermoregulation of cattle raised in integrated crop-livestock-forestry systems. The insights gained from this study may be of assistance to indicate ICLF as a suitable option for increasing animal welfare in tropical climates.

中文翻译：

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Nelore (Bos indicus) 和 Canchim (Bos taurus x Bos indicus) 公牛在热带气候下饲养在综合作物-牲畜-林业系统中的热舒适度

语境

气候变化对牲畜生产力和动物健康提出了挑战。因此，减轻全球气温升高对畜牧业生产影响的管理策略变得越来越重要。然而，尚未更深入地研究使用综合作物-畜牧-林业系统来优化肉牛热平衡。

客观的

该研究旨在评估非遮荫牧场系统 (NS) 和综合作物-牲畜-林业系统 (ICLF) 中的小气候及其在不同气候季节对瘤牛和复合公牛的体温调节和内分泌反应的影响。

方法

该实验是在巴西圣卡洛斯-SP（南纬 21°57′42″，西经 47°50′28″）的热带地区进行的。Nelore ( Bos indicus ) 和 Canchim (5/8 Bos taurus x 3/8 Bos indicus ) 公牛在非阴影系统 (NS; n  = 32) 或综合作物-牲畜-林业系统 (ICLF; n = 32）。每月对动物进行评估，并使用 GLM 模型分析数据。使用 Tukey 检验比较平均值 ( P  < 0.05)。

结果和结论

ICLF 系统降低了空气温度（-0.6 °C；P  = 0.0010）、黑球温度和湿度指数-BGHI（-3.8；P  < 0.0001）和辐射热负荷（-104 W/m ²；P < 0.0001) 与 NS 系统相比。NS 公牛的红外热像图的特征是秋季和冬季背部和躯干表面的温度较高（P  < 0.05）。此外，NS 公牛在 秋季表现出更高的呼吸频率（RR：35.85 ± 0.88 vs 31.97 ± 0.88 次呼吸/分钟； P  = 0.0210）和体内温度（BT：39.54 ± 0.05 vs 39.35 ± 0.05 °C；P = 0.0057） . 皮质醇浓度显着降低（−12.13 ng/mL；P < 0.05) 在整个实验的两个系统中。与 Canchim 公牛相比，Nelore 公牛的 RR 和 BT 较低，皮质醇平均浓度较低，三碘甲腺原氨酸分泌较高。由于自然遮荫的作用，ICLF 系统可有效缓解牧场的微气候，提供更好的热舒适性，特别是对于复合动物而言，并且有利于维持公牛的恒温。

意义

本论文对在农牧林业综合系统中饲养的牛的体温调节所涉及的生理机制提供了更深入的了解。从这项研究中获得的见解可能有助于表明 ICLF 是增加热带气候动物福利的合适选择。