Cao Mengbing, Zong Chao, Zhuang Yanrong, Teng Guanghui, Zhou Shengnan, Yang Ting
College of Water Resources and Civil Engineering, China Agricultural University, Beijing 100083, China.
Key Laboratory of Agricultural Engineering in Structure and Environment, Ministry of Agriculture and Rural Affairs, Beijing 100083, China.
Animals (Basel). 2021 May 21;11(6):1498. doi: 10.3390/ani11061498.
Heat stress has an adverse effect on the production performance of sows, and causes a large economic loss every year. The thermal environment index is an important indicator for evaluating the level of heat stress in animals. Many thermal indices have been used to analyze the environment of the pig house, including temperature and humidity index (THI), effective temperature (ET), equivalent temperature index of sows (ETIS), and enthalpy (H), among others. Different heat indices have different characteristics, and it is necessary to analyze and compare the characteristics of heat indices to select a relatively suitable heat index for specific application. This article reviews the thermal environment indices used in the process of sow breeding, and compares various heat indices in four ways: (1) Holding the value of the thermal index constant and analyzing the equivalent temperature changes caused by the relative humidity. (2) Analyzing the variations of ET and ETIS caused by changes in air velocity. (3) Conducting a comparative analysis of a variety of isothermal lines fitted to the psychrometric chart. (4) Analyzing the distributions of various heat index values inside the sow barn and the correlation between various heat indices and sow heat dissipation with the use of computational fluid dynamics (CFD) technology. The results show that the ETIS performs better than other thermal indices in the analysis of sows' thermal environment, followed by THI2, THI4, and THI7. Different pigs have different heat transfer characteristics and different adaptability to the environment. Therefore, based on the above results, the following suggestions have been given: The thermal index thresholds need to be divided based on the adaptability of pigs to the environment at different growth stages and the different climates in different regions. An appropriate threshold for a thermal index can provide a theoretical basis for the environmental control of the pig house.
热应激对母猪的生产性能有不利影响，每年都会造成巨大的经济损失。热环境指数是评估动物热应激水平的重要指标。许多热指标已被用于分析猪舍环境，包括温度湿度指数（THI）、有效温度（ET）、母猪等效温度指数（ETIS）和焓（H）等。不同的热指标有不同的特点，有必要分析和比较热指标的特点，以便为特定应用选择相对合适的热指标。本文综述了母猪养殖过程中使用的热环境指标，并从四个方面对各种热指标进行了比较：（1）保持热指标值不变，分析相对湿度引起的等效温度变化。（2）分析风速变化引起的ET和ETIS的变化。（3）对拟合到焓湿图上的各种等温线进行对比分析。（4）利用计算流体动力学（CFD）技术分析母猪舍内各种热指标值的分布以及各种热指标与母猪散热之间的相关性。结果表明，在分析母猪热环境方面，ETIS比其他热指标表现更好，其次是THI2、THI4和THI7。不同的猪具有不同的传热特性和对环境的不同适应性。因此，基于上述结果，给出以下建议：需要根据猪在不同生长阶段对环境的适应性以及不同地区的不同气候来划分热指标阈值。热指标的适当阈值可为猪舍的环境控制提供理论依据。
