Created page with "現在家畜を支えている地域の中には、今世紀末の高い温暖化においても「極度の熱ストレス」を回避すると予想される場所もあるが、他の地域では今世紀半ばという早い時期に適さなくなる可能性がある。一般的に、サハラ以南アフリカは、畜産業への気候変動の影響による食料安全保障への打撃に最も脆弱な地域と..."
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現在家畜を支えている地域の中には、今世紀末の高い温暖化においても「極度の熱ストレス」を回避すると予想される場所もあるが、他の地域では今世紀半ばという早い時期に適さなくなる可能性がある。一般的に、[[:en:sub-Saharan Africa|サハラ以南アフリカ]]は、畜産業への気候変動の影響による[[food security/ja|食料安全保障]]への打撃に最も脆弱な地域と考えられている。これらの国々の1億8千万人以上が、今世紀半ば頃に[[:en:rangelands|牧草地]]の適性の大幅な低下を経験すると予想されるためである。一方、日本、米国、ヨーロッパ諸国は最も脆弱でないと考えられている。これは、各国への気候の直接的影響の結果であると同時に、[[:en:human development index|人間開発指数]]やその他の[[:en:community resilience|国家回復力]]の測定値における既存の差異、および国民の食事における[[:en:pastoralism|牧畜]]の重要性の大きな違いの産物でもある。
現在家畜を支えている地域の中には、今世紀末の高い温暖化においても「極度の熱ストレス」を回避すると予想される場所もあるが、他の地域では今世紀半ばという早い時期に適さなくなる可能性がある。一般的に、[[:en:sub-Saharan Africa|サハラ以南アフリカ]]は、畜産業への気候変動の影響による[[food security/ja|食料安全保障]]への打撃に最も脆弱な地域と考えられている。これらの国々の1億8千万人以上が、今世紀半ば頃に[[:en:rangelands|牧草地]]の適性の大幅な低下を経験すると予想されるためである。一方、日本、米国、ヨーロッパ諸国は最も脆弱でないと考えられている。これは、各国への気候の直接的影響の結果であると同時に、[[:en:human development index|人間開発指数]]やその他の[[:en:community resilience|国家回復力]]の測定値における既存の差異、および国民の食事における[[:en:pastoralism|牧畜]]の重要性の大きな違いの産物でもある。
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畜産業における気候変動への適応策の提案には、畜舎での冷却システムの改善や動物用飼料の変更などがあるが、これらはしばしば費用がかかり、効果も限定的である。同時に、畜産業は[[:en:greenhouse gas emissions from agriculture|農業からの温室効果ガス排出]]の大部分を占め、農業の[[:en:fresh water|淡水]]需要の約30%を要求する一方で、世界の[[calorie/ja|カロリー]]摂取量の18%しか供給していない。動物由来の食品は人間の[[protein/ja|タンパク質]]需要の充足においてより大きな役割を果たすが、それでも供給量の39%と少数派であり、残りは作物が提供している。したがって、地球温暖化を{{convert|1.5|C-change|F-change}}や{{convert|2|C-change|F-change}}などのより低いレベルに制限する計画では、動物由来の食品が世界の食事において現在よりも低い役割を果たすと想定されている。そのため、[[:en:net zero|ネットゼロ]]移行計画には総畜産頭数の制限（アイルランドなどの国々における既に不釣り合いに大きな家畜数の削減を含む）が含まれ、世界の多くの場所で現在畜産業者に提供されている[[:en:subsidies|補助金]]の段階的廃止を求める声もある。
Proposed adaptations to climate change in livestock production include improved cooling at animal shelters and changes to animal feed, though they are often costly or have only limited effects. At the same time, livestock produces the majority of [[greenhouse gas emissions from agriculture]] and demands around 30% of agricultural [[fresh water]] needs, while only supplying 18% of the global [[calorie]] intake. Animal-derived food plays a larger role in meeting human [[protein]] needs, yet is still a minority of supply at 39%, with crops providing the rest. Consequently, plans for limiting global warming to lower levels like {{convert|1.5|C-change|F-change}} or {{convert|2|C-change|F-change}} assume animal-derived food will play a lower role in the global diets relative to now. As such, [[net zero]] transition plans now involve limits on total livestock headcounts (including reductions of already disproportionately large stocks in countries like Ireland), and there have been calls for phasing out [[subsidies]] currently offered to livestock farmers in many places worldwide.
[[File:Lallo_2018_Jamaica_livestock_THI.png|thumb|Increased intensity of global climate change causes even greater increases of thermal heat index in Jamaican farm animals. High thermal heat index is one of the more widely used indicators of heat stress.]]
In general, the preferred ambient temperature range for domestic animals is between {{convert|10|and|30|C}}. Much like how climate change is expected to increase overall thermal comfort for humans living in the colder regions of the world, livestock in those places would also benefit from warmer winters. Across the entire world, however, increasing summertime temperatures as well as more frequent and intense heatwaves will have clearly negative effects, substantially elevating the risk of livestock suffering from [[heat stress]]. Under the [[climate change scenario]] of highest emissions and greatest warming, [[Shared Socioeconomic Pathways|SSP5-8.5]], "cattle,sheep, goats, pigs and poultry in the low latitudes will face 72–136 additional days per year of extreme stress from high heat and humidity".
In [[Jamaica]], considered representative of the [[Caribbean]] region, all livestock animals besides layer hens are already exposed to "very severe" heat stress in the present climate, with pigs being exposed to it at least once per day during the 5 summer and early autumn months, while [[ruminant]]s and [[broiler]]s only ''avoid'' daily exposure to very severe heat stress during the winter. it has been projected that even at {{convert|1.5|C-change|F-change}} of global warming, "very severe" heat stress would become a ''daily'' event for [[ruminant]]s and [[broiler]]s. By {{convert|2|C-change|F-change}}, it would be felt for a longer duration, and extensive cooling systems would likely become a necessity for livestock production in the Caribbean. At {{convert|2.5|C-change|F-change}}, only layer hens would avoid daily exposure to "very severe" heat stress during the winter months.
Studies of heat stress and livestock had historically focused on cattle, as they are often kept outdoors and so are immediately exposed to changes in climate. On the other hand, a little over 50% of all pork production and 70% of all poultry production worldwide originated from animals kept entirely in confined buildings even around 2006, and the raw numbers were expected to increase by 3–3.5 times for pigs, by 2–2.4 times for [[layer hen]]s and 4.4–5 times for [[broiler]]s. Historically, livestock in these conditions were considered less vulnerable to warming than the animals in outdoor areas due to inhabiting insulated buildings, where [[ventilation (architecture)|ventilation]] systems are used to control the climate and relieve the excess heat. However, in the historically cooler [[midlatitude]] regions, indoor temperatures were already higher than the outdoor temperatures even in summer, and as the increased heating exceeds these systems' specifications, confined animals are left more vulnerable to the heat than those kept outdoors.
[[File:Lacetera_2018_heat_livestock_diagram.jpeg|thumb|left|upright=1.2|Impacts of heat stress on livestock animals]]
家畜動物の体温が正常値より{{convert|3-4|C-change|F-change}}高くなると、これは間もなく「[[heat stroke/ja|熱射病]]、熱疲労、熱性[[syncope (medicine)/ja|失神]]、[[heat cramps/ja|熱けいれん]]、そして最終的には[[organ dysfunction/ja|臓器機能不全]]」につながる。家畜の死亡率は既に年間で最も暑い月や[[:en:heatwave|熱波]]の際に高いことが知られている。例えば、[[:en:2003 European heat wave|2003年のヨーロッパ熱波]]では、[[:en:Brittany|ブルターニュ]]と[[:en:Pays-de-la-Loire|ペイ・ド・ラ・ロワール]]のフランス地域だけで数千頭の豚、家禽、ウサギが死亡した。
Once the body temperature of livestock animals is {{convert|3-4|C-change|F-change}} above normal, this soon leads to "[[heat stroke]], heat exhaustion, heat [[syncope (medicine)|syncope]], [[heat cramps]], and ultimately [[organ dysfunction]]". Livestock mortality rates are already known to be higher during the hottest months of the year, as well as during [[heatwave]]s. During the [[2003 European heat wave]], for instance, thousands of pigs, poultry, and rabbits died in the French regions of [[Brittany]] and [[Pays-de-la-Loire]] alone.
Livestock can also suffer multiple sublethal impacts from heat stress, such as reduced milk production. Once the temperatures exceed {{convert|30|C}}, cattle, sheep, goats, pigs and chickens all begin to consume 3–5% less feed for each subsequent degree of temperature increase. At the same time, they increase [[respiratory rate|respiratory]] and [[sweating]] rates, and the combination of these responses can lead to [[metabolic disorder]]s. One examples is [[ketosis]], or the rapid accumulation of [[ketone]] bodies, caused by the animal's body rapidly [[catabolism|catabolizing]] its fat stores to sustain itself. Heat stress also causes an increase in [[antioxidant]] [[enzyme]] activities, which can result in an imbalance of oxidant and antioxidant molecules, otherwise known as [[oxidative stress]]. Feed supplementation with [[antioxidant]]s like [[chromium]] can help address oxidative stress and prevent it from leading to other pathological conditions, but only in a limited way.
The [[immune system]] is also known to be impaired in heat-stressed animals, rendering them more susceptible to various infections. Similarly, [[vaccination]] of livestock is less effective when they suffer from heat stress. So far, heat stress had been estimated by researchers using inconsistent definitions, and current livestock models have limited correlation with experimental data. but the first model to do so was only published in 2021, and it still tends to systematically overestimate body temperature while underestimating breathing rate.
[[File:Schauberger_2019_heat_exchanger.png|thumb|This diagram shows a proposed design of a heat exchanger for indoor rearing facilities, whose installation would help to protect livestock from heat stress.]]
In the United States alone, economic losses caused by heat stress in livestock were already valued at between $1.69 and $2.36 billion in 2003, with the spread reflecting different assumptions about the effectiveness of contemporary adaptation measures. Nevertheless, some reviews consider the United States to be the least vulnerable nation to food security shocks caused by the negative impacts of climate change on livestock, as while it rates in the middle of the pack in terms of ''exposure'' of its livestock and the societal ''sensitivity'' to that exposure, it has the highest ''adaptive'' capacity in the world due to its GDP and development status. Japan and the nations in Europe have low vulnerability for similar reasons.
Meanwhile the ''exposure'' of Mongolian livestock to climate change is not very different from that of American livestock, but the enormous importance of [[pastoralism]] in Mongolian society and its limited capacity to adapt still renders it one of the most vulnerable countries in the world. Nations in [[sub-Saharan Africa]] generally suffer from high exposure, low adaptive capacity and high sensitivity due to the importance of livestock in their societies, with these factors particularly acute in Eastern African countries, where between 4 and 19% of livestock-producing areas are expected to suffer "significantly" more "dangerous" heat stress events after 2070, depending on the [[climate change scenario]]. There is ''high confidence'' that under the most intense scenario, [[Shared Socioeconomic Pathways|SSP5-8.5]], the net amount of land which can support livestock will decline by 2050 as heat stress would already become unbearable for them in some locations.
A range of [[climate change adaptation]] measures can help to protect livestock, such as increasing access to drinking water, creating better shelters for animals kept outdoors and improving air circulation in the existing indoor facilities. Installing specialized cooling systems is the most capital-intensive intervention, but it may be able to completely counteract the impact of future warming.
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==家畜の給餌の困難{{Anchor|Difficulties in feeding livestock}}==
==Difficulties in feeding livestock==
===飼料と牧草への気候の影響===
===Climatic impacts on feed and forage===
[[File:Grazing_pasture,_South_Dakota,_USA_(9199).jpg|thumb|サウスダコタ州[[:en:Fall River County|フォールリバーカントリー]]における過放牧対安定牧草地]]
[[File:Grazing_pasture,_South_Dakota,_USA_(9199).jpg|thumb|Overgrazed vs. stable pasture in [[Fall River County]], South Dakota]]
Livestock is fed either by letting them directly graze [[forage]] from pasture, or by growing crops like corn or [[soybean]]s for fodder. Both are highly important; the majority of soybeans are grown for fodder, while a third of croplands worldwide are devoted to forage, which feeds around 1.5 billion cattle, 0.21 billion buffalo, 1.2 billion sheep and 1.02 billion goats. Insufficient supply or quality of either leads to a decrease in growth and reproductive efficiency in domestic animals, especially in conjunction with the other stressors, and at worst, may increase mortality due to starvation. This is a particularly acute issue when livestock herds are already of an unsustainable size. For instance, two-thirds of animal feed requirements in [[Iran]] come from its rangelands, which cover around 52% of its land area, yet only 10% have forage quality above "medium" or "poor". Consequently, Iranian [[rangelands]] support over twice their sustainable capacity, and this leads to mass mortality in poor years, such as when around 800,000 goats and sheep in Iran perished due to the severe 1999 − 2001 drought. This was then exceeded by millions of animal deaths during the 2007–2008 drought.
Climate change can impact livestock animals' food supply in multiple ways. First, the direct effects of temperature increase affect both fodder cultivation and productivity of rangelands, albeit in variable ways. On a global scale, there is confidence that with all else equal, every single {{convert|1|C-change|F-change}} of warming would decrease the yields of the four most important crops by between ~3% for rice and [[soybean]] (a crop grown primarily for animal feed) and up to 6% and 7.4% for wheat and corn respectively. This global decline is dominated by negative impacts in already warm countries, since agriculture in cooler countries is expected to benefit from warming.However, this does not include the impact of changes in water availability, which can be far more important than the warming, whether for pasture species like [[alfalfa]] and [[tall fescue]], or for crops. Some studies suggest that high water availability through [[irrigation]] "decouples" crops from climate as they become much less susceptible to [[extreme weather]] events, but the feasibility of this approach is obviously limited by the region's overall [[water security]], especially once the warming reaches levels of {{convert|2|or|3|C-change|F-change}}.
While climate change increases [[precipitation]] on average, regional changes are more variable, and variability alone adversely impacts "animal fertility, mortality, and herd recovery, reducing livestock keepers' resilience".{{rp|717}} In [[Zimbabwe]], uncertainty about rainfall under different [[climate change scenario]]s could mean the difference between 20% and 100% of farmers negatively affected by 2070, while the average livestock revenue could potentially increase by 6%, yet may also plunge by as much as 43%.
Many places are likely to see increased drought, which would affect both the crops and the pastural land. For instance, in the Mediterranean region, forage yields have already declined by 52.8% during drought years. Drought can also affect [[freshwater]] sources used by people and livestock alike: 2019 drought in Southwestern China caused around 824,000 people and 566,000 livestock to experience severe [[water scarcity]], as over 100 rivers and 180 reservoirs dried out. That event was considered between 1.4 and 6 times more likely to happen as the result of climate change. In the mountain regions, [[mountain glacier|glacier]] melt can also affect pasture, as it first floods the land, and then retreats entirely.
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===大気中の{{CO2}}と畜産飼料===
===Atmospheric {{CO2}} and livestock forage===
飼料と牧草の豊富さは[[:en:CO2 fertilization effect|CO2施肥効果]]から大きく恩恵を受け、これは成長を促進し水利用をより効率的にして、特定の場所（すなわち米国の牧草地の多く）で干ばつの影響に対抗する可能性がある。同時に、これは植物の栄養価の低下も引き起こし、一部の牧草草は特定の条件下（すなわち栄養が既に乏しい秋季）で家畜にとって無用になる可能性がある。混合草[[prairie/ja|プレーリー]]では、日中{{convert|1.5|C-change|F-change}}、夜間{{convert|3|C-change|F-change}}の実験的局地温暖化は、同じ実験中に{{CO2}}レベルを600 [[:en:Parts per million|ppm]]（2023年の約420 ppmレベルより約50%高い）に増加させることと比較して相対的に軽微な効果を持つ。このような大草原における飼料の全体的な成長の96%は、わずか6種の植物種に由来し、{{CO2}}レベルの増加に主に反応して生産性が38%向上する。しかし、同じ理由で家畜にとっての栄養価も13%低下する。これは、食用となる組織の成長が減少し、消化しにくくなるためである。
The abundance of fodder and forage strongly benefits from the [[CO2 fertilization effect]], which boosts growth and makes their water usage more efficient, potentially counteracting the effects of drought in certain places (i.e. many of the United States' rangelands). At the same time, it also causes plants' nutritional value to decline, with some forage grasses potentially becoming useless to livestock under certain conditions (i.e. during autumn, when their nutrition is already poor). On mixed grass [[prairie]]s, experimental local warming of {{convert|1.5|C-change|F-change}} during the day and of {{convert|3|C-change|F-change}} at night has a relatively minor effect in comparison to increasing {{CO2}} levels to 600 [[Parts per million|ppm]] (nearly 50% larger than the ~420 ppm levels of 2023) during the same experiment. 96% of overall forage growth on such prairies stems from just six plant species, and they become 38% more productive largely in response to the increased {{CO2}} levels, yet their nutritious value to livestock also declines by 13% due to the same, as they grow less edible tissue and become harder to digest.
Warming and water deficit also affect nutritional value, sometimes synergistically. For instance, [[Guinea grass]], an important forage plant in the tropics, already gains more inedible [[lignin]] in response to water deficit (+43%), as well as in response to warming (+25%). Its lignin content increases the least in response to both stressors (+17%), yet elevated {{CO2}} further reduces its nutritional value, even as it makes the plant less susceptible to water stress. Similar response was observed in ''[[Stylosanthes]] capilata'', another important forage species in the tropics, which is likely to become more prevalent with warming, yet which may require irrigation to avoid substantial losses in nutritional value.
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===家畜の栄養低下による地球規模への影響===
===Global impacts of lowered livestock nutrition===
[[File:Weindl_2015_livestock_by_2045.jpg|thumb|Impacts of one possible scenario of climate change on agricultural costs between 2005 and 2045, under a range of assumptions about the role of CO2 fertilization effect and the effectiveness of adaptation strategies]]
Altogether, around 10% of ''current'' global pasture is expected to be threatened by water scarcity caused by climate change, as early as 2050. By 2100, 30% of the ''current'' combined crop and livestock areas would become climatically unsuitable under the warmest scenario [[Shared Socioeconomic Pathways|SSP5-8.5]], as opposed to 8% under the low-warming SSP1-2.6, although neither figure accounts for the potential shift of production to other areas. If {{convert|2|C-change|F-change}} of warming occurs by 2050, then 7–10% of the current livestock are predicted to be lost primarily due to insufficient feed supply, amounting to $10–13 billion in lost value.
Similarly, an older study found that if {{convert|1.1|C-change|F-change}} of warming occurs between 2005 and 2045 (rate comparable to hitting {{convert|2|C-change|F-change}} by 2050), then under the current livestock management paradigm, global agricultural costs would increase by 3% (an estimated $145 billion), with the impact concentrated in pure pasturalist systems. At the same time, mixed crop-livestock systems already produced over 90% of the global milk supply as of 2013, as well as 80% of ruminant meat, yet they would bear the minority of the costs, and switching all pure livestock systems to mixed crop-livestock would decrease global agricultural costs from 3% to 0.3%, while switching half of those systems would reduce costs to 0.8%. The full shift would also reduce future projected [[deforestation]] in the tropics by up to 76 million [[hectare|ha]].
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==病原体と寄生虫==
==Pathogens and parasites==
{{See also/ja|Climate change and infectious diseases}}
{{See also|Climate change and infectious diseases}}
気候による熱ストレスは家畜の全疾病に対する免疫力を直接的に低下させる一方で、気候要因は多くの家畜病原体自体の分布にも影響を与える。例えば、東アフリカにおける[[Rift Valley fever/ja|リフトバレー熱]]の流行は、干ばつ時や[[:en:El Nino|エルニーニョ]]現象発生時により激しくなることが知られている。別の例として、ヨーロッパの[[:en:helminth|蠕虫]]は現在より高緯度地域まで拡散しており、生存率の向上と繁殖能力（[[:en:fecundity|繁殖力]]）の増加を示している。ヨーロッパにおける家畜疾病と様々な農業介入の詳細な長期記録により、家畜の蠕虫負担増加における気候変動の役割を実証することは、実際には人間に影響を与える疾病への気候変動の影響を帰属させるよりも容易である。
While climate-induced heat stress can directly reduce domestic animals' immunity against all diseases, climatic factors also impact the distribution of many livestock pathogens themselves. For instance, [[Rift Valley fever]] outbreaks in East Africa are known to be more intense during the times of drought or when there is an [[El Nino]]. Another example is that of [[helminth]]s in Europe which have now spread further towards the poles, with higher survival rate and higher reproductive capacity ([[fecundity]]). Detailed long-term records of both livestock diseases and various agricultural interventions in Europe mean that demonstrating the role of climate change in the increased helminth burden in livestock is actually easier than attributing the impact of climate change on diseases which affect humans.
[[File:FCO-brebis.jpg|thumb|ブルータング・ウイルスに感染した羊]]
[[File:FCO-brebis.jpg|thumb|A sheep infected with bluetongue virus]]
Temperature increases are also likely to benefit [[Culicoides imicola]], a species of [[midge]] which spreads [[bluetongue virus]]. [[Ixodes ricinus]], a [[tick]] which spreads pathogens like [[Lyme disease]] and [[tick-borne encephalitis]], is predicted to become 5–7% more prevalent on livestock farms in Great Britain, depending on the extent of future climate change.
The impacts of climate change on [[leptospirosis]] are more complicated: its outbreaks are likely to worsen wherever flood risk increases, yet the increasing temperatures are projected to reduce its overall incidence in the Southeast Asia, particularly under the high-warming scenarios.
Under high warming, there will be a global decline in area suitable for [[shellfish]] aquaculture after 2060. It will be preceded by regional declines in Asia. [[Farmed fish]] can be affected by heat stress as much as any other animal, and there has already been research on its effects and ways to mitigate it in species like [[tambaqui]] or blunt snout [[bream]].
Along with camels, goats are more resilient to drought than cattle. In Southeastern [[Ethiopia]], some of the cattle pastoralists are already switching to goats and camels.
As of 2009, there were 1.2 billion cattle in the world, with around 82% in the [[developing countries]]; the totals only increased since then, with the 2021 figure at 1.53 billion. As of 2020, it was found that in the current Eastern [[Mediterranean]] climate, cattle experience ''mild'' heat stress inside unadapted stalls for nearly half a year (159 days), while ''moderate'' heat stress is felt indoors and outdoors during May, June, July, August, September, and October. Additionally, June and August are the months where cattle are exposed to ''severe'' heat stress outside, which is mitigated to moderate heat stress indoors. Even ''mild'' heat stress can reduce the yield of [[cow milk]]: research in Sweden found that average daily temperatures of {{convert|20-25|C}} reduce daily milk yield per cow by {{convert|200|g|lb|abbr=on}}, with the loss reaching {{convert|540|g|lb|abbr=on}} for {{convert|25-30|C}}.
Research in a humid tropical climate describes a more linear relationship, with every unit of heat stress reducing yield by 2.13%. In the [[intensive farming]] systems, daily milk yield per cow declines by {{convert|1.8|kg|lb|abbr=on}} during severe heat stress. In [[organic farming]] systems, the effect of heat stress on milk yields is limited, but milk ''quality'' suffers substantially, with lower fat and [[protein]] content. In China, daily milk production per cow is already lower than the average by between {{convert|0.7|and|4|kg|lb|abbr=on}} in July (the hottest month of the year), and by 2070, it may decline by up to 50% (or {{convert|7.2|kg|lb|abbr=on}}) due to climate change. Some researchers suggest that the already recorded stagnation of dairy production in both China and West Africa can attributed to persistent increases in heat stress.
Heatwaves can also reduce milk yield, with particularly acute impacts if the heatwave lasts for four or more days, as at that point the cow's thermoregulation capacity is usually exhausted, and its core body temperature starts to increase. At worst, heatwaves can lead to mass mortality: in July 1995, over 4,000 cattle in the mid-central [[United States]] heatwave, and in 1999, over 5,000 cattle died during a heatwave in northeastern [[Nebraska]]. Studies suggest that [[Brahman cattle]] and its cross-breeds are more resistant to heat stress than the regular ''bos taurus'' breeds, but it is considered unlikely that even more heat-resistant cattle can be bred at a sufficient rate to keep up with the expected warming. Further, both male and female cattle can have their reproduction impaired by heat stress. In males, severe heat can affect both [[spermatogenesis]] and the stored [[spermatozoa]]. It may take up to eight weeks for sperm to become viable again. In females, heat stress negatively affects [[conception (biology)|conception]] rates as it impairs [[corpus luteum]] and thus [[ovarian]] function and [[oocyte]] quality. Even after conception, a pregnancy is less likely to be carried to term due to reduced [[endometrial]] function and [[uterine]] blood flow, leading to increased embryonic mortality and early fetal loss. Calves born to heat-stressed cows typically have a below-average weight, and their weight and height remains below average even by the time they reach their first year, due to permanent changes in their [[metabolism]]. Heat-stressed cattle have also displayed reduced [[albumin]] secretion and liver [[enzyme]] activity. This is attributed to accelerated breakdown of [[adipose tissue]] by the liver, causing [[lipidosis]].
[[Image:Mamite å colibacile laecea.jpg|thumb|left|150px|牛の''[[E. coli/ja|大腸菌]]''性乳房炎における乳房からの漿液性[[exudate/ja|滲出液]]（左）と正常乳（右）との比較]]
[[Image:Mamite å colibacile laecea.jpg|thumb|left|150px|Serous [[exudate]] from udder in ''[[E. coli]]'' mastitis in cow (left), in comparison to normal milk (right)]]
牛は[[rumen/ja|ルーメン]]性[[acidosis/ja|アシドーシス]]などの特定の熱ストレスリスクに感受性がある。牛は1日の最暑時間帯に急性熱ストレスを経験すると摂食量が減少し、涼しくなった時に補償するが、この不均衡はすぐにアシドーシスを引き起こし、[[laminitis/ja|蹄葉炎]]につながる可能性がある。さらに、牛が高温に対処しようとする方法の1つが[[:en:Thermoregulation#Endothermy|パンティング]]の頻度増加であり、これにより[[carbon dioxide/ja|二酸化炭素]]濃度が急速に低下し、[[pH/ja|pH]]が上昇する。呼吸性[[alkalosis/ja|アルカローシス]]を避けるため、牛は[[urination/ja|排尿]]を通じて[[bicarbonate/ja|重炭酸塩]]を排出することを余儀なくされ、これは[[rumen/ja|ルーメン]]の緩衝能力を犠牲にして行われる。これらの病理学的変化の両方が[[:en:lameness|跛行]]に発展する可能性があり、これは「動物が歩行方法を変える原因となるあらゆる足の異常」と定義される。この影響は重度の熱ストレス曝露後「数週間から数か月」で現れ、痛みを伴う[[ulcer|潰瘍]]や[[white line disease/ja|白線病]]を伴う。もう1つの特定のリスクは[[mastitis in dairy cattle/ja|乳牛の乳房炎]]であり、これは通常、牛の[[udder/ja|乳房]]への外傷または「乳頭管への細菌侵入に対する免疫応答」によって引き起こされる。高温では牛の[[neutrophil/ja|好中球]]機能が阻害され、[[mammary gland/ja|乳腺]]が感染により脆弱になる。乳房炎はすでに夏季により蔓延することが知られているため、気候変動の継続によりこれが悪化することが予想される。
Cattle are suspectible to some specific heat stress risks, such as [[rumen|ruminal]] [[acidosis]]. Cattle eat less when they experience acute heat stress during hottest parts of the day, only to compensate when it is cooler, and this disbalance soon causes acidosis, which can lead to [[laminitis]]. Additionally, one of the ways cattle can attempt to deal with higher temperatures is by [[Thermoregulation#Endothermy|panting more often]], which rapidly decreases [[carbon dioxide]] concentrations and increases [[pH]]. To avoid respiratory [[alkalosis]], cattle are forced to shed [[bicarbonate]] through [[urination]], and this comes at the expense of [[rumen]] buffering. These two pathologies can both develop into [[lameness]], defined as "any foot abnormality that causes an animal to change the way that it walks". This effect can occur "weeks to months" after severe heat stress exposure, alongside sore [[ulcer]]s and [[white line disease]]. Another specific risk is [[mastitis in dairy cattle|mastitis]], normally caused by either an injury to cow's [[udder]], or "immune response to bacterial invasion of the teat canal." Bovine [[neutrophil]] function is impaired at higher temperatures, leaving [[mammary gland]]s more vulnerable to infection, and mastitis is already known to be more prevalent during the summer months, so there is an expectation this would worsen with continued climate change.
One of the vectors of bacteria which cause mastitis are [[Calliphora]] blowflies, whose numbers are predicted to increase with continued warming, especially in the temperate countries like the United Kingdom. [[Rhipicephalus microplus]], a [[tick]] which primarily parasitises cattle, could become established in the currently [[temperate]] countries once their autumns and winters become warmer by about {{convert|2-2.75|C-change|F-change}}. On the other hand, the brown stomach worm, [[Ostertagia ostertagi]], is predicted to become much less prevalent in cattle as the warming progresses.
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2017年までに、ネパールの農家は長期化する暑季による損失のため、飼育する牛の数を減らしていることがすでに報告された。[[:en:Wyoming|ワイオミング]]州南東部の牛・子牛牧場は、[[:en:hydrological cycle|水文循環]]がより変動的になり牧草の成長に影響を与えるため、将来より大きな損失を被ることが予想される。年間「平均」降水量はそれほど変化しないと予想されるものの、異常に乾燥した年と異常に湿潤した年が増加し、負の影響が正の影響を上回る。乾燥年に対応するためより柔軟性を持たせるために小規模な群れを維持することが適応戦略として提案された。より変動的で予測困難な降水は[[:en:effects of climate change on the water cycle|気候変動の水循環への影響]]の確立された現象の1つであるため、類似のパターンが後にアメリカ合衆国全体で確立された。
By 2017, it was already reported that farmers in Nepal kept fewer cattle due to the losses imposed by a longer hot season. Cow-calf ranches in Southeast [[Wyoming]] are expected to suffer greater losses in the future as the [[hydrological cycle]] becomes more variable and affects forage growth. Even though the annual ''mean'' precipitation is not expected to change much, there will be more unusually dry years as well as unusually wet years, and the negatives will outweigh the positives. Keeping smaller herds to be more flexible when dry years hit was suggested as an adaptation strategy. Since more variable and therefore less predictable precipitation is one of the well-established [[effects of climate change on the water cycle]], similar patterns were later established across the rest of the United States,
[[File:Liu 2024 climate beef.png|thumb|All but two or three of the top 10 beef-producing countries are likely to see lower production with greater warming.]]
As of 2022, it has been suggested that every additional millimeter of annual precipitation increases beef production by 2.1% in the tropical countries and reduces it by 1.9% in temperate ones, yet the effects of warming are much larger. Under [[Shared Socioeconomic Pathways|SSP3-7.0]], a scenario of significant warming and very low adaptation, every additional {{convert|1|C-change|F-change}} would decrease global beef production by 9.7%, mainly because of its impact on tropical and poor countries. In the countries which can afford adaptation measures, production would fall by around 4%, but by 27% in those which cannot. In 2024, another study suggested that the impacts would be milder - a 1% decrease per every additional {{convert|1|C-change|F-change}} in low-income countries and 0.2% in high-income ones, and a 3.2% global decline in beef production by 2100 under SSP3-7.0. The same paper suggests that out of the top 10 beef-producing countries (Argentina, Australia, Brazil, China, France, India, Mexico, Russia, Turkey and the U.S.), only China, Russia and the U.S. would see overall production gains with increased warming, with the rest experiencing declines. Other research suggests that east and south of Argentina may become more suitable to cattle ranching due to climate-driven shifts in rainfall, but a shift to [[Zebu]] breeds would likely be needed to minimize the impact of warming.
As of 2019, there are around 17 million horses in the world. Healthy body temperature for adult horses is in the range between {{convert|37.5|and|38.5|C}}, which they can maintain while ambient temperatures are between {{convert|5|and|25|C}}. However, strenuous exercise increases core body temperature by {{convert|1|C-change|F-change}}/minute, as 80% of the energy used by equine muscles is released as heat. Along with [[bovine]]s and [[primate]]s, equines are one of the very few animal groups which use [[sweating]] as their primary method of thermoregulation: in fact, it can account for up to 70% of their heat loss, and horses sweat three times more than humans while undergoing comparably strenuous physical activity. Unlike that of humans, this sweat is created not by [[Eccrine gland|eccrine glands]] but by [[Apocrine|apocrine glands]]. In hot conditions, horses during three hours' moderate-intensity exercise can lose 30 to 35 L of water and 100g of sodium, 198 g of choloride and 45 g of potassium. In another difference from humans, their sweat is [[hypertonic]], and contains a protein called [[BPIFA4P|latherin]], which enables it to spread across their body easier, and to [[foam]], rather than to drip off. These adaptations are partly to compensate for their lower body surface-to-mass ratio, which makes it more difficult for horses to passively radiate heat. Yet, prolonged exposure to very hot and/or humid conditions will lead to consequences such as [[anhidrosis]], [[heat stroke]], or brain damage, potentially culminating in death if not addressed with measures like cold water applications. Additionally, around 10% of incidents associated with horse transport have been attributed to heat stress. These issues are expected to worsen in the future.
[[African horse sickness]] (AHS) is a viral illness with a mortality close to 90% in horses, and 50% in [[mule]]s. A midge, [[Culicoides imicola]], is the primary vector of AHS, and its spread is expected to benefit from climate change. The spillover of [[Hendra virus]] from its [[flying fox]] hosts to horses is also likely to increase, as future warming would expand the hosts' geographic range. It has been estimated that under the "moderate" and high [[climate change scenario]]s, [[Representative Concentration Pathway|RCP4.5]] and RCP8.5, the number of threatened horses would increase by 110,000 and 165,000, respectively, or by 175 and 260%.
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=== ヤギと羊 ===
=== Goats and sheep ===
[[File:Sheep and cattle at a feedlot in Colorado (9381).jpg|thumb|left|羊は牛よりも暑さに対する耐性が高いことで知られている。]]
[[File:Sheep and cattle at a feedlot in Colorado (9381).jpg|thumb|left|Sheep are known for tolerating heat better than cattle.]]
Goats and sheep are often collectively described as ''small ruminants'', and tend to be studied together rather than separately. with goats in particular considered one the most climate-resilient domestic animals, being second only to camels. In Southeastern [[Ethiopia]], some of the cattle pastoralists are already switching to goats and camels.
Even so, the 2007–2008 drought in Iran had already resulted in the country's sheep population declining by nearly 4 million – from 53.8 million in 2007 to 50 million in 2008, while the goat population declined from 25.5 million in 2007 to 22.3 million in 2008. Some researchers expect climate change to drive genetic selection towards more heat- and drought-adapted breeds of sheep. Notably, heat-adapted sheep can be of both [[wool]] and hair breeds, in spite of the popular perception that hair breeds are always more resistant to heat stress.
Parasitic worms [[Haemonchus contortus]] and [[Teladorsagia circumcincta]] are predicted to spread more easily amongst small ruminants as the winters become milder due to future warming, although in some places this is counteracted by summers getting hotter than their preferred temperature. Earlier, similar effects have been observed with two other parasitic worms, [[Parelaphostrongylus odocoilei]] and [[Protostrongylus stilesi]], which have already been able to reproduce for a longer period inside sheep due to milder temperatures in the [[sub-Arctic]].
For pigs, heat stress varies depending on their age and size. Young and growing pigs with the average body mass of {{convert|30|kg|lb|abbr=on}} can tolerate temperatures up to {{convert|24|C}} before starting to experience any heat stress, but after they have grown and are fattened to about {{convert|120|kg|lb|abbr=on}}, at which point they are considered ready for slaughter, their tolerance drops to just {{convert|20|C}}.
One paper estimated that in Austria, at an intensive farming facility used to fatten up about 1800 growing pigs at a time, the already observed warming between 1981 and 2017 would have increased relative annual heat stress by between 0.9 and 6.4% per year. It is considered representative of other such facilities in Central Europe.
A follow-up paper considered the impact of several adaptation measures. Installing a [[ground-coupled heat exchanger]] was the most effective intervention at addressing heat stress, reducing it by 90 to 100%. Two other cooling systems also showed substantial effectiveness: [[evaporative cooler]] pads made of wet [[cellulose]] reduced heat stress by 74 to 92%, although they also risked increasing [[wet bulb temperature]] stress as they necessarily moistened the air. Combining such pads with [[regenerative heat exchanger]]s eliminated this issue, but also increased costs and reduced the effectiveness of the system to between 61% and 86%. All three interventions were considered capable of completely buffering the future impact of climate change on heat stress over at least the next three decades, but installing them requires substantial start-up investments, and their impact on commercial viability of the facilities is unclear. Other interventions were considered unable to fully buffer the impact of warming, but they were also cheaper and simpler by comparison. They include doubling the ventilation capacity, and having the pigs rest during the day while feeding them at night when it is cooler: such a 10-hour shift would require that the facility only uses [[artificial light]] and switch to predominantly [[Night working|night shift]] work. Similarly, stocking fewer pigs per facility is the absolute simplest intervention, yet it has the lowest effectiveness, and necessarily reduces profitability.
It is believed that the thermal comfort zone for poultry is in the {{convert|18-25|C}} range. Some papers describe {{convert|26-35|C}} as the "critical zone" for [[heat stress]], but others report that due to [[acclimatization]], birds in the tropical countries do not begin to experience heat stress until {{convert|32|C}}. There is wider agreement that temperatures greater than {{convert|35|C}} and {{convert|47|C}} form "upper critical" and lethal zones, respectively. Average daily temperatures of around {{convert|33|C}} are known to interfere with feeding in both [[broiler]]s and egg hens, as well as lower their [[immune response]], with outcomes such as reduced weight gain/egg production or greater incidence of [[salmonella]] infections, [[footpad]] [[dermatitis]] or [[meningitis]]. Persistent heat stress leads to [[oxidative stress]] in tissues, and harvested [[white meat]] ends up with a lower proportion of essential compounds like [[vitamin E]], [[lutein]] and [[zeaxanthin]], yet an increase in [[glucose]] and [[cholesterol]]. Multiple studies show that dietary supplementation with [[chromium]] can help to relieve these issues due to its [[antioxidative]] properties, particularly in combination with [[zinc]] or herbs like [[wood sorrel]]. [[Resveratrol]] is another popular antioxidant administered to poultry for these reasons. Though the effect of supplementation is limited, it is much cheaper than interventions to improve cooling or simply stock fewer birds, and so remains popular. While the majority of literature on poultry heat stress and dietary supplementation focuses on chickens, similar findings were seen in [[Japanese quail]]s, which eat less and gain less weight, suffer reduced [[fertility]] and hatch [[egg]]s of worse quality under heat stress, and also seem to benefit from mineral supplementation.
Around 2003, it was estimated that the poultry industry in the United States already lost up to $165 million annually due to heat stress at the time. One paper estimated that if global warming reaches {{convert|2.5|C-change|F-change}}, then the cost of rearing broilers in Brazil increases by 35.8% at the least modernized farms and by 42.3% at farms with the medium level of technology used in livestock housing, while they increase the least at farms with the most advanced cooling technologies. On the contrary, if the warming is kept to {{convert|1.5|C-change|F-change}}, costs at moderately modernized farms increase the least, by 12.5%, followed by the most modernized farms with a 19.9% increase, and the least technological farms seeing the greatest increase.
By mid-2010s, indigenous people of the Arctic have already observed [[reindeer]] breeding less and surviving winters less often, as warmer temperatures benefit biting insects and result in more intense and persistent swarm attacks. They also become more susceptible to parasites spread by such insects, and as the Arctic becomes warmer and more accessible to [[invasive species]], it is anticipated that they will come in contact with pests and pathogens they have not encountered historically.
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==畜産活動による温室効果ガス排出量==
==Greenhouse gas emissions from livestock activities==
{{excerpt|Greenhouse gas emissions from agriculture/ja#畜産|paragraphs=1-4|file=no}}
{{excerpt|Greenhouse gas emissions from agriculture#Livestock|paragraphs=1-4|file=no}}
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<span id="See_also"></span>
== See also ==
== 関連項目 ==
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* [[:en:Economic impacts of climate change|気候変動の経済的影響]]
* [[Economic impacts of climate change]]
* [[:en:Effects of climate change on agriculture|気候変動が農業に及ぼす影響]]
畜産業における気候変動への適応策の提案には、畜舎での冷却システムの改善や動物用飼料の変更などがあるが、これらはしばしば費用がかかり、効果も限定的である。同時に、畜産業は農業からの温室効果ガス排出の大部分を占め、農業の淡水需要の約30%を要求する一方で、世界のカロリー摂取量の18%しか供給していない。動物由来の食品は人間のタンパク質需要の充足においてより大きな役割を果たすが、それでも供給量の39%と少数派であり、残りは作物が提供している。したがって、地球温暖化を1.5 °C (2.7 °F)や2 °C (3.6 °F)などのより低いレベルに制限する計画では、動物由来の食品が世界の食事において現在よりも低い役割を果たすと想定されている。そのため、ネットゼロ移行計画には総畜産頭数の制限（アイルランドなどの国々における既に不釣り合いに大きな家畜数の削減を含む）が含まれ、世界の多くの場所で現在畜産業者に提供されている補助金の段階的廃止を求める声もある。
一般的に、家畜にとって好ましい周囲温度範囲は10 and 30 °C (50 and 86 °F)の間である。気候変動により世界の寒冷地域に住む人間の全体的な温熱快適性が向上すると予想されるのと同様に、それらの地域の家畜も暖かい冬から恩恵を受けるであろう。しかし、世界全体では、夏季の気温上昇やより頻繁で激しい熱波が明らかに負の効果をもたらし、家畜の熱ストレスリスクを大幅に増加させる。最高排出量で最大の温暖化を想定した気候変動シナリオであるSSP5-8.5の下では、「低緯度地域の牛、羊、山羊、豚、家禽は、高温多湿による極度のストレスを年間72-136日多く受ける」ことになる。
カリブ海地域を代表すると考えられるジャマイカでは、採卵鶏を除くすべての家畜動物が現在の気候において既に「極度に深刻な」熱ストレスにさらされており、豚は夏季と初秋の5ヶ月間少なくとも1日1回これにさらされる一方、反芻動物とブロイラーは冬季のみ極度に深刻な熱ストレスへの毎日の曝露を回避している。1.5 °C (2.7 °F)の地球温暖化でも、「極度に深刻な」熱ストレスが反芻動物とブロイラーにとって日常的な出来事になると予測されている。2 °C (3.6 °F)では、それはより長い期間感じられ、広範囲な冷却システムがカリブ海における畜産業に必要となる可能性が高い。2.5 °C (4.5 °F)では、採卵鶏のみが冬季の「極度に深刻な」熱ストレスへの毎日の曝露を避けることになる。
家畜は熱ストレスによる乳生産量の減少など、複数の致死に至らない影響を受けることもある。気温が30 °C (86 °F)を超えると、牛、羊、山羊、豚、鶏はすべて、その後の気温上昇の度に3-5%少ない飼料を摂取し始める。同時に、これらの動物は呼吸と発汗の速度を増加させ、これらの反応の組み合わせが代謝障害につながる可能性がある。例の一つはケトーシス、すなわち動物の体が自分を維持するために脂肪蓄積を急速に異化することによって引き起こされるケトン体の急速な蓄積である。熱ストレスはまた抗酸化酵素活性の増加を引き起こし、これは酸化物質と抗酸化分子の不均衡、すなわち酸化ストレスとして知られる状態を引き起こす可能性がある。クロムなどの抗酸化物質による飼料補給は酸化ストレスに対処し、それが他の病理学的状態につながることを防ぐのに役立つが、限定的な方法でのみである。
気候変動は家畜動物の食料供給に複数の方法で影響を与える可能性がある。第一に、気温上昇の直接的効果は飼料栽培と牧草地の生産性の両方に影響を与えるが、その方法は様々である。地球規模では、他の条件が等しければ、1 °C (1.8 °F)の温暖化ごとに最も重要な4つの作物の収量が、コメと大豆（主に動物用飼料として栽培される作物）で約3%から、小麦とトウモロコシではそれぞれ最大6%と7.4%まで減少するという確信がある。この世界的な減少は既に暖かい国々における負の影響に支配されており、涼しい国々の農業は温暖化から恩恵を受けると予想されるためである。しかし、これは水利用可能性の変化の影響を含んでおらず、これはアルファルファやトールフェスクなどの牧草種や作物にとって温暖化よりもはるかに重要である可能性がある。一部の研究では、灌漑による高い水利用可能性は作物を気候から「切り離し」、異常気象事象に対してはるかに影響を受けにくくすることを示唆しているが、このアプローチの実現可能性は明らかに地域の全体的な水安全保障によって制限され、特に温暖化が2 or 3 °C (3.6 or 5.4 °F)のレベルに達した場合はそうである。
総合すると、気候変動によって引き起こされる水不足により、現在の世界の牧草地の約10%が2050年にも脅威にさらされると予想されている。2100年には、現在の作物栽培面積と家畜飼育面積を合わせたものの30%が、最も温暖なシナリオであるSSP5-8.5の下では気候的に不適格となる。これは、低温暖化シナリオであるSSP1-2.6の下での8%とは対照的である。ただし、どちらの数値も生産が他の地域に潜在的にシフトする可能性を考慮していない。2050年までに2 °C (3.6 °F)の温暖化が発生した場合、現在の家畜の7〜10%が主に飼料供給の不足により失われると予測されており、その損失額は100億から130億ドルに上る。
同様に、以前の研究では、2005年から2045年の間に 1.1 °C (2.0 °F)の温暖化（2050年までに2 °C (3.6 °F)に達する速度に匹敵する）が発生した場合、現在の家畜管理の枠組みでは、世界の農業コストが3%（推定1450億ドル）増加し、その影響は純粋な放牧システムに集中するとされている。同時に、混合作物-家畜システムは、2013年時点で世界の牛乳供給の90%以上、反芻動物の肉の80%をすでに生産しているが、これらのシステムが負担するコストは少数にとどまる。そして、すべての純粋な家畜システムを混合作物-家畜システムに切り替えると、世界の農業コストは3%から0.3%に減少し、それらのシステムの半分を切り替えることでコストは0.8%に削減される。この完全な移行は、熱帯地域における将来予測される森林破壊を最大7600万ha削減することにもなる。
2009年時点で、世界には12億頭の牛が存在し、そのうち約82%が開発途上国にいた。その後も総数は増加し続け、2021年の数字は15.3億頭に達した。2020年時点で、現在の東地中海気候では、牛は適応されていない牛舎内で年間の約半分（159日間）にわたって「軽度の」熱ストレスを経験し、「中等度の」熱ストレスは5月、6月、7月、8月、9月、10月の屋内外で感じられることが判明した。さらに、6月と8月は牛が屋外で「重度の」熱ストレスにさらされる月であり、これは屋内では中等度の熱ストレスまで軽減される。「軽度の」熱ストレスでさえ牛乳の収量を減少させる。スウェーデンでの研究では、平均日気温が20–25 °C (68–77 °F)の場合、1頭当たりの1日の乳量が200 g (0.44 lb)減少し、25–30 °C (77–86 °F)では損失が540 g (1.19 lb)に達することが判明した。
湿潤熱帯気候での研究では、より線形の関係が記述されており、熱ストレスの1単位当たり収量が2.13%減少する。集約農業システムでは、重度の熱ストレス時に1頭当たりの1日の乳量が1.8 kg (4.0 lb)減少する。有機農業システムでは、熱ストレスが乳量に与える影響は限定的であるが、乳「品質」は大幅に低下し、脂肪とタンパク質含量が減少する。中国では、1頭当たりの1日の乳生産量がすでに7月（年間最暑月）に平均より0.7 and 4 kg (1.5 and 8.8 lb)少なく、2070年までには気候変動により最大50%（または7.2 kg (16 lb)）減少する可能性がある。一部の研究者は、中国と西アフリカ両地域ですでに記録されている酪農生産の停滞を、持続的な熱ストレス増加に起因するものと示唆している。
2022年時点で、年間降水量の追加ミリメートル当たり、熱帯諸国では牛肉生産が2.1%増加し、温帯諸国では1.9%減少するが、温暖化の影響ははるかに大きいことが示唆されている。大幅な温暖化と極めて低い適応を想定したSSP3-7.0シナリオ下では、追加の1 °C (1.8 °F)当たり世界の牛肉生産が9.7%減少し、これは主に熱帯および貧困国への影響による。適応措置を講じることができる国では生産量は約4%減少するが、そうでない国では27%減少する。2024年の別の研究では、影響はより軽微であると示唆され、低所得国では追加の1 °C (1.8 °F)当たり1%減少、高所得国では0.2%減少し、SSP3-7.0下で2100年までに世界の牛肉生産が3.2%減少するとされた。同論文は、上位10の牛肉生産国（アルゼンチン、オーストラリア、ブラジル、中国、フランス、インド、メキシコ、ロシア、トルコ、アメリカ）のうち、中国、ロシア、アメリカのみが温暖化進行により全体的な生産増加を見込める一方、残りは減少を経験すると示唆している。他の研究では、気候による降雨パターンの変化によりアルゼンチンの東部と南部が牛牧畜により適するようになる可能性があるが、温暖化の影響を最小限に抑えるためにゼブ品種への転換が必要になると示唆されている。
馬類
馬の体温調節の図解
2019年時点で、世界には約1,700万頭の馬が存在する。成馬の健康な体温は37.5 and 38.5 °C (99.5 and 101.3 °F)の範囲であり、環境温度が5 and 25 °C (41 and 77 °F)の間である限りこの体温を維持できる。しかし、激しい運動は中核体温を1 °C (1.8 °F)/分上昇させる。これは馬の筋肉で使用されるエネルギーの80%が熱として放出されるためである。ウシや霊長類とともに、馬類は発汗を体温調節の主要な方法として使用する数少ない動物群の1つである。実際、発汗は熱損失の最大70%を占める可能性があり、馬は同程度に激しい身体活動を行う人間の3倍発汗する。人間とは異なり、この汗はエクリン腺ではなくアポクリン腺によって産生される。暑い条件下では、3時間の中等度強度の運動中に馬は30〜35リットルの水分と100グラムのナトリウム、198グラムの塩化物、45グラムのカリウムを失う可能性がある。人間との別の違いは、馬の汗が高張性であり、ラテリンと呼ばれるタンパク質を含んでいることである。これにより汗が体全体により容易に広がり、滴り落ちるのではなく泡立つことが可能になる。これらの適応は、体表面積対質量比が低いために馬が受動的に熱を放射することが困難であることを部分的に補償している。しかし、非常に暑いまたは湿潤な条件への長期間の曝露は、無汗症、熱射病、または脳損傷などの結果を招き、冷水の適用などの措置が講じられなければ死に至る可能性がある。さらに、馬の輸送に関連する事故の約10%が熱ストレスに起因している。これらの問題は将来悪化することが予想される。
家禽の熱的快適域は18–25 °C (64–77 °F)の範囲であると考えられている。一部の論文では26–35 °C (79–95 °F)を熱ストレスの「臨界域」として記述しているが、順化により熱帯諸国の鳥類は32 °C (90 °F)まで熱ストレスを経験しないとする報告もある。35 °C (95 °F)および47 °C (117 °F)を超える温度がそれぞれ「上部臨界」および致死域を形成することについては、より広い合意がある。約33 °C (91 °F)の平均日気温はブロイラーと採卵鶏の両方の摂食を妨害し、免疫応答を低下させることが知られており、体重増加/卵生産の減少やサルモネラ感染、フットパッド皮膚炎、髄膜炎の発症率増加などの結果をもたらす。持続的な熱ストレスは組織の酸化ストレスを引き起こし、収穫された白身肉はビタミンE、ルテイン、ゼアキサンチンなどの必須化合物の割合が低下する一方、グルコースとコレステロールが増加する。複数の研究により、クロムの食餌補充がその抗酸化特性により、特に亜鉛やカタバミなどのハーブと組み合わせることで、これらの問題の緩和に役立つことが示されている。レスベラトロールも同じ理由で家禽に投与される人気の抗酸化剤である。補充の効果は限定的であるが、冷却改善や単純に飼育鳥数を減らすなどの介入よりもはるかに安価であるため、依然として人気がある。家禽の熱ストレスと食餌補充に関する文献の大部分はニワトリに焦点を当てているが、ウズラでも同様の知見が見られた。ウズラは熱ストレス下で摂食量と体重増加が減少し、繁殖力が低下し、品質の劣る卵を孵化させるが、ミネラル補充から恩恵を受けるようである。
2003年頃、アメリカ合衆国の家禽産業は当時すでに熱ストレスにより年間最大1億6,500万ドルの損失を被っていると推定された。ある論文は、地球温暖化が2.5 °C (4.5 °F)に達した場合、ブラジルでのブロイラー飼育コストが最も近代化の遅れた農場で35.8%、畜舎技術の中程度レベルを使用する農場で42.3%増加する一方、最先端の冷却技術を持つ農場では最も少ない増加となると推定した。
反対に、温暖化が1.5°C（2.7°F）に抑えられた場合、適度に近代化された農場でのコスト増加が最も少なく12.5%となり、次いで最も近代化された農場が19.9%増加し、最も技術が低い農場での増加が最大となる。
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