Extreme Heat Is Devastating Farmed Animals Worldwide

Extreme heat is no longer a future threat to farmed animals. It’s an escalating crisis unfolding right now, and its impacts on cows, pigs, sheep, goats, and chickens are already widespread and well documented. This joint report from the Food and Agriculture Organization of the United Nations and the World Meteorological Organization provides a sweeping assessment of how extreme heat is reshaping life for these animals across every environment.

Relying primarily on scientific literature, the report focuses on vulnerabilities, observed impacts, and future projections related to extreme heat across agricultural subsectors. While the report is framed around food production and food security, its findings about animal suffering and mortality are striking on their own terms.

All major farmed species, including cows, pigs, sheep, goats, and chickens, have defined thermoneutral ranges above which heat stress sets in. For unacclimated cows, sheep, and goats, the upper thermoneutral threshold is 25 °C; for pigs and chickens, who can’t sweat, it’s slightly lower at 24 °C.

As temperatures rise above these thresholds, animals seek shade, move around less, and drink more. When this is no longer enough, their bodies begin to expend more energy to cool themselves. Food intake is reduced by 3% to 5% with each additional degree above 30 °C and productivity declines. Without relief from the heat, they suffer increasingly severe physiological consequences, including immune suppression, organ failure, cardiovascular shock, and death.

The productivity losses from heat stress are well researched, particularly in the dairy industry. Milk from heat-stressed dairy animals contains lower fat and protein, egg shells become thinner, and wool and meat quality deteriorates. For dairy cows specifically, milk yields drop roughly 2% per additional unit of heat stress, and these losses can persist for days after the heat event ends. Heat stress experienced during their dry period (the weeks before calving) reduces their milk production in future lactation cycles as well.

Reproduction is severely affected. Across species, heat-stressed mothers experience higher rates of embryo mortality, shorter gestation periods, and reduced litter sizes. Intergenerational effects compound the damage: offspring born to heat-stressed mothers have lower birth and weaning weights, shorter life expectancies, and reduced productivity as adults. These aren’t transient losses — they represent lasting biological harm passed across generations.

Extreme heat also harms farmed animals indirectly through their feed. Forage grown under heat-stressed conditions contains less protein and more fiber, making it harder to digest and less nutritious — leading to lower milk yields, reduced weight gain, and in ruminants, more methane produced during digestion. For sheep and goats, the extra metabolic work of digesting poor-quality feed generates additional body heat, compounding their vulnerability to high temperatures. Rising atmospheric carbon dioxide levels further reduce the protein content of grains like barley and wheat commonly fed to pigs and chickens. On top of this, warmer conditions increase the prevalence of mycotoxins in grain, which can weaken farmed animals’ immune systems and increase their susceptibility to disease.

Extreme heat can trigger mass mortality events. A study of mortality in 46,000 dairy cows, for example, found that they were 20% more likely to die during a heatwave, with deaths continuing to occur at significant levels for three days after the heatwave ended. In poultry production, heatwave-induced deaths have reached into the millions. Confinement — feedlots, transport vehicles, slaughter facilities — consistently amplifies mortality risk.

Looking ahead, the projections are stark. Under a high-emissions scenario, for instance, cows in tropical regions could face near-perpetual heat stress by 2100. However, under a low-emissions scenario, the projected heat risk for cows would be reduced by at least 50% in Asia, 63% in South America, and 84% in Africa. Overall, between 61% and 75% of the global population of cows, pigs, sheep, goats, and chickens could be exposed to extreme heat-stress days by 2090 under a high-emissions scenario, compared to 17% to 31% under a low-emissions scenario — underscoring how dramatically emission reductions can limit animal suffering.

The report acknowledges several gaps in the current evidence base. No studies have examined the differential impacts of sustained heatwave exposure versus an accumulation of unrelated hot days — a distinction that matters for understanding how animals experience and recover from extreme heat. Impacts on animals managed under extensive free-range conditions are also less well documented than those in confined systems, due to observational data constraints. Projected impacts of extreme heat on farmed animal diseases and pests like flies and ticks also remain understudied.

Even though it’s framed around food security, this report is deeply relevant for animal advocates. The suffering documented here is vast in scale and growing, with billions of farmed animals under threat from extreme heat due to climate change. The report is also unequivocal that these harms can be meaningfully reduced through emission reductions.

This evidence supports not only welfare reform within existing systems, such as shade structures, cooling systems, and early warning systems, but also the stronger argument that animal agriculture itself is deeply entangled with the climate crisis. Raising more animals under increasingly heat-stressed conditions to compensate for productivity losses drives land-use expansion, which generates more greenhouse gas emissions, which drives more extreme heat. Advocates can use these findings to make the case that the most effective long-term intervention for animal welfare is one that addresses the root cause: a decisive reduction in both emissions and the scale of animal use.

This summary was drafted by a large language model (LLM) and closely edited by our Research Library Manager for clarity and accuracy. As per our AI policy, Faunalytics only uses LLMs to summarize very long reports (50+ pages) that are not appropriate to assign to volunteers, as well as studies that contain graphic descriptions of animal cruelty or animal industries. We remain committed to bringing you reliable data, which is why any AI-generated work will always be reviewed by a human.