The effects of climate change on livestock are mostly indirect, through food production (cereals, forage, pastures). However, there are also direct impacts such as lower productivity associated to higher temperatures during the summer. This lower productivity can be thee consequence of a lower thermal comfort of animals (THI, Temperature-Humidity Index), lower fertility rate, or an increase of vector-borne diseases.
Regarding the Temperature-Humidity Index (THI), livestock production is affected negatively by heat. In intensive production systems, heat stress can reduce milk production and growing rate of pigs by daily mean temperatures over 18 and 21 degrees Celsius respectively. High temperatures and humidity also increased livestock mortality by 60% in Italy.
Climate change can also affect milk production negatively in the Southern region due to heat stress on dairy cows (IPCC, 2014). In fact, it is estimated that up to 10% of variability in milk production comes as a consequence of climatic factors such as temperature.
The reduction of milk production in situations of heat stress comes due to the reduction in food consumption, while the energy needs of the livestock increase. Furthermore, heat stress reduces the concentration of protein and fat in milk, inhibits rumination and causes immunosuppression, increasing the impacts of certain diseases. Finally, heat stress reduces drastically reproductive indexes, since the reduction in synthesis of hormones such as LH and GnRH inhibits ovulation and expression of the estrus conduct.
Regarding the increase of diseases, climate change will bring to Europe important displacements of the seasonal ranges of distribution of vector-borne diseases. For example, climate can affect diseases by shortening the life cycles of vectors and the incubation periods of pathogens, which will lead to a potential increase of vector populations and a higher risk of transmission.
In the long run, seasonal changes may affect both vectors and hosts, as well as human activities on land. Therefore, this will also influence geographical distribution, seasonal activity and general prevalence of diseases transmitted by vectors in Europe (EEA, 2012).
Focusing on indirect impacts, livestock husbandry systems are very exposed to the impacts of climate change at local (pastures and crops) and global scale (imported concentrated feedstuffs), mainly due to their dependence on yield and quality of crops and pastures. This means that a lower or poor quality production in pastures, fodder and grain, will compromise the livestock husbandry activity by itself.
Source: Baseline Report AgriAdapt and FAWEC
https://agriadapt.eu/wp-content/uploads/2017/04/A1_Baseline-report_Full-version_V3.pdf