The effect of heat stress on productivity and fertility in dairy cows and pigs

Due to global warming, the thermal stress of farm animals in form of heat stress will increase in importance even in the temperate climate zones of Central Europe. High-yielding animals in open barn husbandry systems, i.e., especially dairy cows, are particularly affected by this. However, studies also show that there can be significant effects in animals kept in closed systems, i.e., under relatively controlled environmental conditions. These include high-yielding breeding sows, which, like cows, already experience excessive thermal stress due to their increased metabolic performance. To estimate the consequences of thermal stress, scientific studies commonly use temperature-humidity indices (THI), a combination of temperature and relative humidity (RH). Based on these indices, many studies highlight that heat stress affects performance, feed intake, and animal health, reproduction and welfare in both dairy cows and pigs. This literature review describes the effects of heat stress on the technological characteristics and qualities of milk from dairy cows, as well as fertility, health and welfare in dairy cows and breeding sows. In order to counteract the problem of heat stress, there are several possibilities to make suitable adjustments at different levels of animal production. These include feeding (e.g. fodder production), husbandry (e.g. air-conditioned housing) and animal management (e.g. fertility management, breeding).