Effect of two cooling systems on thyroid hormones and thermophysiological variables of lactating sows

ABSTRACT The effects of the evaporative cooling system with negative pressure (ECS) and water spray on the roof (WSR) on physiological variables, thyroid hormones and neutrophil/lymphocyte ratio (N:L) in lactating sows were evaluated. Sixty-one lactating females were divided in the two thermal environments, being 30 in SRE and 31 in the AAT shed in the summer. The air temperature and humidity, respiratory frequency (RF), surface temperatures (ST) and rectal (RT), serum thyroxine and triiodothyronine concentration, number of neutrophils and lymphocytes and the N/L ratio were determined. In the afternoon, the matrices in ECS (Tar: 25.0°C and THI: 74.7) and WSR (Tar: 27.6°C and THI: 77.3) were exposed to heat stress. In the morning, RF, ST and RT were lower in ECS (49 breaths.min -1 , 31.1°C and 38.5°C, respectively) than WSR (54 breaths.min -1 , 32.8°C and 38.6°C) and also in the afternoon ECS (55 breaths.min -1 , 30.3°C and 38.8°C, respectively) and WSR (65 breaths.min -1 , 31.4°C and 39.1°C, respectively). Animals under WSR shed presented lower concentrations of T4 than animals under ECS (37.84 vs 42.22nmol.L -1 ). In a tropical environment, in the summer, lactating sows of both systems maintain homeothermia.

摘要：本研究评估了负压蒸发冷却系统（ECS）与屋顶喷水降温系统（WSR）对泌乳母猪生理指标、甲状腺激素及中性粒细胞/淋巴细胞比值（N:L）的影响。夏季共纳入61头泌乳母猪，分为两种热环境处理组：30头饲养于SRE舍，31头饲养于AAT舍。测定指标包括温湿度、呼吸频率（RF）、体表温度（ST）与直肠温度（RT）、血清甲状腺素与三碘甲状腺原氨酸浓度、中性粒细胞与淋巴细胞计数及N:L比值。午后时段，ECS组（舍内气温25.0℃、温湿指数74.7）与WSR组（舍内气温27.6℃、温湿指数77.3）的受试母猪均处于热应激状态。晨间时段，ECS组母猪的呼吸频率（49次·分钟⁻¹）、体表温度（31.1℃）与直肠温度（38.5℃）均低于WSR组（分别为54次·分钟⁻¹、32.8℃与38.6℃）；午后时段，ECS组母猪上述指标分别为55次·分钟⁻¹、30.3℃与38.8℃，同样低于WSR组的65次·分钟⁻¹、31.4℃与39.1℃。WSR组母猪的血清甲状腺素（T4）浓度低于ECS组（37.84 vs 42.22nmol·L⁻¹）。在热带夏季环境中，两种降温系统饲养的泌乳母猪均可维持体温稳态。