Pantoja Messy Hannear de Andrade, Campos Jessica Caetano Dias, Almeida Douglas Henrique Silva de, Negrão João Alberto, Mourão Gerson Barreto, Pereira Alfredo Manuel Franco, Titto Cristiane Gonçalves
Faculdade de Zootecnia e Engenharia de Alimentos/ Universidade de São Paulo, Av. Duque de Caxias Norte, 225, Campus Fernando Costa, Pirassununga, SP, 13635-900, Brazil.
Escola Superior de Agricultura Luiz de Queiroz/ Universidade de São Paulo, Av. Pádua Dias, 11, Piracicaba, SP, 13418900, Brazil.
J Therm Biol. 2023 Jan;111:103420. doi: 10.1016/j.jtherbio.2022.103420. Epub 2022 Dec 5.
The frequency of heat waves has increased over the last years, with an impact on animal production and health, including the death of animals. Therefore, the aim of this study was to evaluate the dynamics of thermoregulation and hormonal responses in non-pregnant and pregnant ewes exposed to successive heat waves. Twenty-four non-pregnant and 18 pregnant Santa Ines ewes with black coat color (live weight: 55 ± 9.03 kg; age: 60 months) were used. Weather variables such air temperature, relative humidity, and solar radiation were continuously recorded. The rectal and tympanic temperatures and respiratory rate were measured daily. Serum triiodothyronine (T3) and prolactin were evaluated during the heat wave and thermoneutral periods. The physiological variables were higher under the heat wave conditions and were related to the activation of the thermoregulatory system for maintaining homeothermy (P < 0.05). The core body temperature was higher during successive heat waves (P < 0.05), as was the tympanic temperature, which are both affected by changes in air temperature (P < 0.05). T3 and prolactin levels were not influenced by successive heat waves (P < 0.05) and rectal temperature and respiratory rate were highest in non-pregnant ewes (P < 0.05). Prolactin was not affected by temperature. The results indicate that the Santa Ines breed overcomes the thermal challenge during a heat wave without showing severe signs of thermal stress regardless of being pregnant or not.
在过去几年中，热浪发生的频率有所增加，对动物生产和健康产生了影响，包括动物死亡。因此，本研究的目的是评估暴露于连续热浪中的未怀孕和怀孕母羊的体温调节动态和激素反应。使用了24只未怀孕和18只怀孕的黑色被毛圣伊内斯母羊（体重：55±9.03千克；年龄：60个月）。持续记录气温、相对湿度和太阳辐射等气象变量。每天测量直肠温度、鼓膜温度和呼吸频率。在热浪期和热中性期评估血清三碘甲状腺原氨酸（T3）和催乳素。在热浪条件下，生理变量较高，这与维持体温恒定的体温调节系统的激活有关（P<0.05）。连续热浪期间，核心体温较高（P<0.05），鼓膜温度也较高，两者均受气温变化影响（P<0.05）。连续热浪对T3和催乳素水平没有影响（P<0.05），直肠温度和呼吸频率在未怀孕母羊中最高（P<0.05）。催乳素不受温度影响。结果表明，无论是否怀孕，圣伊内斯品种在热浪期间都能克服热应激挑战，而不表现出严重的热应激迹象。
