In this study we compared the bio-thermal responses of a crossbred (F1, Nellore x Angus) and purebred Bos indicus (Nellore) cattle kept under moderate thermal conditions. Specifically, we assessed if they were different in their daily pattern of metabolic heat production, regulation of body temperature and use of evaporative heat transfer pathways. Six Nellore bulls with 669 ± 65 kg of body weight and twelve crossbred bulls (F1, Nellore x Angus) with 606.5 ± 25.09 kg of body weight, were evaluated in two experiments. Individual bulls were secured and attached to instruments in the biometeorology laboratory to enable recording of the proportion of respiratory gases in the exhaled air (oxygen, O₂; carbon dioxide, CO₂), saturation pressure of the exhaled air (P_S{T_EXP}, kPa) and skin surface (P_S{T_SKIN}, kPa), respiratory rate (R_R, breath min⁻¹), ventilation rate (V_E, L s⁻¹); skin (T_SKIN,°C), hair coat (T_S,°C), rectal (T_R,°C) and exhaled air temperatures (T_EXP,°C) from 0600 to 1800 h. The air temperature over the two experiments ranged from 16 to 30°C. The mean of metabolic heat production was higher for crossbred (2.24 W kg⁻¹) than Nellore cattle (1.09 W kg⁻¹) (P <0.0001), as the crossbred had higher values ​​for ventilation rate (P <0.0001), and proportion of the oxygen extracted from the inhaled air. Slight differences for thermal storage and daily fluctuation of daytime rectal temperature (0730 and 1630 h) were also observed, ranging from 39 to 39.30°C for Nellore cattle and from 39.12 to 39.62°C for the crossbred. Both genotypes increased heat loss through cutaneous evaporation with rising air temperature, which was slightly higher for the crossbred cattle. In conclusion, under the moderate thermal conditions of the present study, the crossbred cattle had higher levels of heat production, thermal storage and cutaneous evaporation than the purebred Nellore cattle. Further, it appears that both genotypes were able to maintain their thermal balance with relatively low energy demand for thermoregulation.

在这项研究中，我们比较了饲养在中等温度条件下的杂交牛（F1，Nellore x Angus）和纯种印度s牛（Nellore）的生物热响应。具体来说，我们评估了它们在日常代谢热产生，体温调节和蒸发热传递途径的使用方面是否存在差异。在两个实验中评估了六只体重为669±65千克的内洛尔公牛和十二头体重为606.5±25.09千克的杂种公牛（F1，内洛尔x安格斯）。将多头公牛固定并固定在生物气象实验室的仪器上，以记录呼出空气中呼吸气体的比例（氧气，O ₂；二氧化碳，CO ₂），呼出空气的饱和压力（P_小号【T _EXP }，千帕）和皮肤表面（P_小号【T _SKIN }，千帕），呼吸率（R _[R ，呼吸分钟^-1），通风量（V _ê，L小号^-1）; 皮肤（T _SKIN，°C），毛发外套（T _S，°C），直肠（T _R，°C）和呼出空气温度（T _EXP，°C）为0600至1800 h。两次实验的空气温度范围为16至30°C。杂种的代谢热产生平均值（2.24 W kg ^-1）高于内洛尔牛（1.09 W kg ^-1））（P <0.0001），因为杂种的通气率（P <0.0001）和从吸入空气中提取的氧气比例较高。还观察到蓄热的细微差异以及白天直肠温度（0730和1630 h）的每日波动，内洛尔牛的温度范围为39至39.30°C，杂种牛的范围为39.12至39.62°C。两种基因型都会随着皮肤温度的升高而通过皮肤蒸发增加热量损失，而杂种牛的热量损失略高。总之，在本研究的中等温度条件下，杂种牛比纯种内罗尔牛具有更高的产热，蓄热和皮肤蒸发水平。进一步，