Effects of climate change on livestock: Difference between revisions

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{{Short description|Effects of climate change on livestock rearing}}

{{for|contributions of livestock activities to climate change|Greenhouse gas emissions from agriculture}}

[[File:Godber_2014_livestock_impacts_map.jpg|thumb|upright=1.4|Map of countries considered most and least vulnerable to adverse impacts of climate change on their grazing livestock~~<ref name="Godber2014" />~~]]

[[File:Godber_2014_livestock_impacts_map.jpg|thumb|upright=1.4|Map of countries considered most and least vulnerable to adverse impacts of climate change on their grazing livestock]]

There are numerous interlinked '''effects of climate change on livestock''' rearing. This activity is both heavily affected by and a substantial driver of anthropogenic [[climate change]] due to its [[Greenhouse gas emissions from agriculture#Livestock|greenhouse gas emissions]]. As of 2011, some 400 million people relied on livestock in some way to secure their livelihood. The commercial value of this sector is estimated as close to $1 [[trillion]]. As an outright end to human consumption of meat and/or animal products is not currently considered a realistic goal, any comprehensive [[climate change adaptation|adaptation]] to [[effects of climate change]] must also consider livestock.

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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.~~<ref name="Bett2017" />~~ 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.~~<ref name="Lacetera2018" />~~ 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.

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.

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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.<ref>{{Cite journal |vauthors=Ding Y, Hayes MJ, Widhalm M |year=2011 |title=Measuring economic impacts of drought: A review and discussion |url=http://digitalcommons.unl.edu/natrespapers/196 |journal=Disaster Prevention and Management |volume=20 |issue=4 |pages=434–446 |doi=10.1108/09653561111161752|bibcode=2011DisPM..20..434D |url-access=subscription }}</ref> For instance, in the Mediterranean region, forage yields have already declined by 52.8% during drought years.~~<ref name="Liu2022" />~~ 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.~~<ref name="AR6_WGII_Chapter5" />{{rp|724}}~~

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.

===Atmospheric {{CO2}} and livestock forage===

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===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.~~<ref name="AR6_WGII_Chapter5" />{{rp|717}}~~ 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.

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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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,~~<ref name="Bett2017" />~~ yet the increasing temperatures are projected to reduce its overall incidence in the Southeast Asia, particularly under the high-warming scenarios.

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.

== By type of livestock ==

=== Aquaculture ===

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.~~<ref name="AR6_WGII_Chapter5" />{{rp|725}}~~ [[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]].

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]].

=== Camels ===

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=== Cattle ===

[[File:Lacetera_2018_cattle_stress_diagram.jpeg|thumb|right|Various pathologies which can be caused by heat stress, many specific to cattle]]

As of 2009, there were 1.2 billion cattle in the world, with around 82% in the [[developing countries]];~~<ref name="Gaughan2009" />~~ 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}}.

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.~~<ref name="Lees2019" />~~ 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]].

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|Serous [[exudate]] from udder in ''[[E. coli]]'' mastitis in cow (left), in comparison to normal milk (right)]]

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.

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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.~~<ref name="Rose2015" />~~ 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]].

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]].

=== Pigs ===

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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.~~<ref name="Oladokun2022" />~~ 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.

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.

=== Reindeer ===

@@ Line 1: / Line 1: @@
 {{Short description|Effects of climate change on livestock rearing}}
 {{for|contributions of livestock activities to climate change|Greenhouse gas emissions from agriculture}}
-[[File:Godber_2014_livestock_impacts_map.jpg|thumb|upright=1.4|Map of countries considered most and least vulnerable to adverse impacts of climate change on their grazing livestock<ref name="Godber2014" />]]
+[[File:Godber_2014_livestock_impacts_map.jpg|thumb|upright=1.4|Map of countries considered most and least vulnerable to adverse impacts of climate change on their grazing livestock]]
 [[File:Lacetera_2018_climate_livestock_diagram.jpeg|thumb|upright=1.4|right|Multi-faceted [[Effects of climate change|impacts of climate change]] on livestock]]
 There are numerous interlinked '''effects of climate change on livestock''' rearing. This activity is both heavily affected by and a substantial driver of anthropogenic [[climate change]] due to its [[Greenhouse gas emissions from agriculture#Livestock|greenhouse gas emissions]]. As of 2011, some 400 million people relied on livestock in some way to secure their livelihood. The commercial value of this sector is estimated as close to $1 [[trillion]]. As an outright end to human consumption of meat and/or animal products is not currently considered a realistic goal, any comprehensive [[climate change adaptation|adaptation]] to [[effects of climate change]] must also consider livestock.
@@ Line 25: / Line 25: @@
 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.<ref name="Bett2017" /> 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.<ref name="Lacetera2018" /> 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.
+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.
@@ Line 46: / Line 46: @@
 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.<ref>{{Cite journal |vauthors=Ding Y, Hayes MJ, Widhalm M |year=2011 |title=Measuring economic impacts of drought: A review and discussion |url=http://digitalcommons.unl.edu/natrespapers/196 |journal=Disaster Prevention and Management |volume=20 |issue=4 |pages=434–446 |doi=10.1108/09653561111161752|bibcode=2011DisPM..20..434D |url-access=subscription }}</ref> For instance, in the Mediterranean region, forage yields have already declined by 52.8% during drought years.<ref name="Liu2022" /> 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.<ref name="AR6_WGII_Chapter5" />{{rp|724}}
+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.
 ===Atmospheric {{CO2}} and livestock forage===
@@ Line 55: / Line 55: @@
 ===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.<ref name="AR6_WGII_Chapter5" />{{rp|717}} 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&nbsp;billion in lost value.
+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&nbsp;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&nbsp;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]].
@@ Line 65: / Line 65: @@
 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,<ref name="Bett2017" /> yet the increasing temperatures are projected to reduce its overall incidence in the Southeast Asia, particularly under the high-warming scenarios.
+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.
 == By type of livestock ==
 === Aquaculture ===
-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.<ref name="AR6_WGII_Chapter5" />{{rp|725}} [[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]].
+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]].
 === Camels ===
@@ Line 77: / Line 77: @@
 === Cattle ===
 [[File:Lacetera_2018_cattle_stress_diagram.jpeg|thumb|right|Various pathologies which can be caused by heat stress, many specific to cattle]]
-As of 2009, there were 1.2&nbsp;billion cattle in the world, with around 82% in the [[developing countries]];<ref name="Gaughan2009" /> the totals only increased since then, with the 2021 figure at 1.53&nbsp;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}}.
+As of 2009, there were 1.2&nbsp;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&nbsp;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.<ref name="Lees2019" /> 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]].
+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|Serous [[exudate]] from udder in ''[[E. coli]]'' mastitis in cow (left), in comparison to normal milk (right)]]
 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.
@@ Line 103: / Line 103: @@
 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&nbsp;million in 2007 to 50&nbsp;million in 2008, while the goat population declined from 25.5&nbsp;million in 2007 to 22.3&nbsp;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.<ref name="Rose2015" /> 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]].
+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]].
 === Pigs ===
@@ Line 117: / Line 117: @@
 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&nbsp;million annually due to heat stress at the time.<ref name="Oladokun2022" /> 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.
+Around 2003, it was estimated that the poultry industry in the United States already lost up to $165&nbsp;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.
 === Reindeer ===