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This module uses the definition of animal genetic resources that was used in the Second Report on the State of the World’s Animal Genetic Resources for Food and Agriculture: 

Food production from livestock is heavily concentrated in a small group of species. While more than 30 mammalian and bird species have been domesticated, three species (cattle, chickens and pigs) account for about 88 percent of the world’s annual meat production from livestock; two species (cattle and buffaloes) for about 96 percent of milk production; and just one species (chickens) for about 92 percent of egg production (FAO, 2017a). Animal genetic resources include more than 8 800 livestock breeds. In the Executive Brief for the Global Strategy for the Management of Farm Animal Genetic Resources, a breed is defined as:

Single breeds, such as the Holstein dairy cattle and the commercial Leghorn chicken reported in 132 and 52 countries, respectively, account for a large proportion of the production of particular commodities, particularly in highly commercialized production systems. 

For breeds that are raised in extensive conditions, climate is a key element of the production environment. If climatic conditions change rapidly, the adaptive link between a livestock population and its local production environment may be broken. This rupture, which will contribute to a loss of adaptedness, productivity and fitness in local breeds, may cause livestock keepers to change their breed or species, migrate to other areas, or cease livestock production entirely (Box B8.2). In Mauritania for instance, a change in species can be observed between 1994 and 2014, the number of cattle has decreased from 2.3 to 1.9 million heads, while the number of camels has increased from 0.6 to 1.5 million heads (FAOSTAT, 2016), presumably due in part to changes in climate.

Heat stress affects animals in a number of ways. It increases their water requirements, reduces their feed intake and physical activity, and increases their expenditure of metabolic energy to regulate body temperature. All of the effects of heat stress lead to declines in production and fertility, and increases in mortality. In the tropics and subtropics, in particular, rising temperatures will create significant problems for livestock production. Death of animals during extreme heat waves is already a serious risk in feedlots (Hatfield et al., 2008) and confined production environments in countries, such as the United States of America.  

In general, high-output breeds from temperate regions are not well adapted to the effects of high temperatures, high humidity and poor feeding. Increased temperatures associated with climate change are likely to exacerbate the problem of heat stress in these animals unless their management is modified to protect them. Under favourable circumstances, this is technically feasible, for example, by adjusting the animals’ diets to easily digestible feed that generates less heat, and introducing cooling technologies, such as ventilation fans, water sprays or misters. However, for many producers, the costs of these measures may be prohibitive.

Extreme climatic events, such as droughts, floods and hurricanes, have the potential to kill large numbers of animals. If a breed population is concentrated within a limited geographical area, it may be devastated, or even completely wiped out, by a climatic disaster. Climate change is predicted to increase the frequency and severity of climatic disasters, heightening the risk to vulnerable breed populations. 

As discussed in chapter B2 - 2.2, the spread of pathogens or even small spatial or seasonal changes in disease distribution may expose livestock populations that lack resistance or acquired immunity to new animal diseases. A major outbreak of a serious animal disease can pose a catastrophic threat to the livelihoods of livestock producers, particularly if large numbers of animals have to be slaughtered to prevent the further spread of the disease. The extent to which climate change will increase the threat that epidemics pose to livestock diversity is uncertain. However, it is likely that the distribution of diseases spread by vectors, such as insects and ticks, will be influenced by climate. Some worrying recent developments, such as the spread of bluetongue virus in Europe, may be linked to climate change.

Outcomes in terms of disease epidemiology are difficult to predict because of the complexities of interactions between pathogens, vectors and host animals, and other components within an ecosystem, and the influence of a broad range of external factors and management measures. The expected increase in outbreaks of livestock diseases, some of them novel, will favour genotypes that are resistant or tolerant to the diseases in question (Hoffmann, 2010a).

Livestock are major consumers of crops. Any negative impacts of climate change on plant genetic resources used for feed, such as reduced availability, altered nutritional content and increased costs, will also affect livestock production (see chapter B8 - 3). Climatic conditions will also have an impact on the growth of pastures, which can be expected to influence the productivity of grazing livestock and contribute to changes in the geographical areas to which specific breeds of livestock are adapted.

Substantial additional efforts are required to characterize the phenotypic characteristics of livestock breeds, especially in relation to survival, fecundity and performance in specific production environments and their degree of adaptedness to specific diseases and tolerance or resistance to particular diseases (FAO, 2015d). The Domestic Animal Diversity Information System (DAD-IS), which contributes to monitoring livestock breeds nationally and globally, includes a database of information on national breed populations from all around the world (FAO, 2015d). Genetic characterization, using DNA information to discern the relationships among adaptive phenotypes and diversity at the molecular level, may also help improve the management of animal genetic resources with respect to climate change.

Characterization of animal genetic resources has been carried out for many years, both on the phenotypic and genetic levels. Initial studies concentrated on phenotypes related to appearance, morphology and production, and simple genotypes involving a small number of markers sufficient to characterize basic aspects of genetic diversity (for a review, see Groeneveld et al., 2010). However, recent advances in molecular biotechnologies that have allowed for the genotyping of individual animals have created greater opportunities to study functional characteristics of animal populations. Concurrent developments in geographic information systems have permitted the assignment of biological samples (and thus animals and populations) to geographic positions, facilitating the association of breeds and their genotypes with environmental and climatic variables. The application of these technologies has already yielded insights into the genetic basis for adaptations of specific breeds to their environments (e.g. Benjelloun et al., 2015; Gorkhali et al., 2016). The newest genomic technologies also provide results that are more robust and consistent across laboratories, allowing for a meta-analysis of studies undertaken in different geographic regions, and enhancing the understanding of adaptation to climatic conditions in common across continents. For example, the international ADAPTmap project (Stella, 2014) has gathered genomic and geographical data from studies for 144 breeds of goats from 37 countries and six continents and combined them with regular agricultural activities to create a unique resource for studying livestock adaptation.

Many livestock-keeping communities have considerable experienced in managing their livestock in harsh and fluctuating environments. The may do this, for example, by raising several types of species or breeds and/or migrating with their animals to areas with the most favourable conditions (see chapter B2 - 3.2 on risk management and system changes for climate-smart livestock production). Nonetheless, rapid and substantial changes to local climates may outstrip the capacity of animal populations to adapt through natural or human selection. Also, livestock keepers may not be able to adapt their husbandry practices or find a suitable production environment quickly enough to keep pace with these changes. This situation may create the need to find replacements for current livestock breeds and or species. Substitutions of this kind present a significant challenge. Great care must be taken to ensure that introduced species and breeds are well adapted to local conditions and that the original species and breeds do not become extinct.

In different animal breeds, there are many populations, particularly in mountainous and arid areas, that are good walkers and well adapted to extreme ranges in temperature. These breeds, which can deal with coarse vegetation, have low water requirements and can survive on poor quality fodder, may merit further research. The genetic strategy for adaptation includes the development of breed improvement programmes, which involves potentially crossbreeding different breeds, and the substitution of different breed or species for less well-adapted animals. Among the key influential factors for the success of adaptation strategies are the expected rate of climate change and the speed with which genetic change can realistically occur. Substitution and cross-breeding can expedite genetic change, but their implementation may be more complex than pure-breeding and require additional research (e.g. on genotype and environment interaction) (Boettcher et al., 2014). Genomic selection has the potential to accelerate both pure- and cross-breeding programmes for adaptation, if phenotypic data based on performance recording are available. In the longer term, highly advanced technologies, such as genome editing and cloning, may complement traditional methods of breeding to enhance the development of adapted livestock populations.

Local livestock breeds and populations may possess specific phenotypes related to adaptedness that could be used to cope with environment change. Between 2000 and 2015, the inheritance mode of a growing number of those traits was identified, as illustrated in Table B8.2.

Globally, cattle are the major source for enteric methane emissions (Smith et al., 2014). Dietary manipulation and improved feeding systems can reduce methane emissions and nitrogenous emissions and contribute to climate change mitigation. A better understanding of the micro-organisms involved in the digestive processes in the rumen will provide a basis for interventions that improve the efficiency of digestion and reduce the amount of pollutants produced by ruminant livestock (McSweeney and Mackie, 2012).

In addition to selecting traits for increased production, any selection that reduces mortality and increases early maturity, fertility and longevity tends to contribute to increasing the animal's input conversion efficiency (i.e. less greenhouse gases are emitted per unit of food production) (Hoffmann, 2010b). Since the 1940s, improved nutrition, breeding for high performance and improved feed-conversion ratio, and better hygienic management to decrease illness and mortality, have significantly reduced the amount of feed (and land needed to produce this feed) per unit of product. This reduction was greater in monogastrics and dairy cattle than in beef cattle or sheep. Based on data from the United States of America, the carbon footprint for producing a given quantity of milk decreased by 63 percent between 1944 and 2007 owing to improvements in genetics and animal husbandry (Capper et al., 2009). See module B2 for a comprehensive overview of the mitigation possibilities in the livestock sector.

Given the impact of livestock on climate, the inclusion of environmental impacts in breeding goals could be considered. However, trade-offs between the breeding goals and the traits selected need to be taken into account. Negative correlations exist between several traits, for example, production, environmental load, robustness. Generally, the more productive breeds show better input conversion efficiency, but these animals require more inputs in absolute terms and often show limited robustness. Reduced robustness may require management actions to avoid losses tied to poor survival and fertility. Highly productive breeds also tend to yield only a single product, such as meat, milk or eggs, whereas local breeds often provide multiple products and a range of other benefits, including landscape maintenance, wealth protection and cultural preservation. The definition of 'more productive' must be sufficiently inclusive, and take into account not only the value of provisioning services, such as food and fibre, but also the value of other ecosystem services (see module B7 for climate change impacts on soil and land resources, and chapter B2 - 4.1 for the management practices for grazing and pasture management). Moreover, any kind of genetic selection, be it within or across breeds, decreases genetic diversity. The improvements in mitigation described by Capper, Cady and Bauman (2009) were accompanied by a similarly large decrease in the range of breeds commonly used for dairy production, with the Holstein cow being more favoured. There were also large decreases of variation within breeds. This loss of diversity comes with a corresponding loss of adaptive capacity, as discussed in chapter B8 - 2.

When considering greenhouse gas emissions from enteric fermentation, attention should be paid not only of differences within and across breeds in the gross efficiency of converting feed inputs to produce animal-based foods for humans, but also of differences among species in their ability to use forage plants that cannot otherwise be used by humans.

For animal genetic resources, the combination of both in situ and ex situ conservation measures is viewed as the optimal way to protect endangered breeds from extinction and ensuring they continue to deliver ecosystem services. This involves a wide range of measures, including incentives to maintain breeds at risk, conservation breeding, awareness raising activities, the promotion of agrotourism and niche marketing of livestock products. The cryoconservation of semen or embryos, which is described in the Global Plan of Action for Animal Genetic Resources (FAO, 2007), is another possible conservation pathway. Recent assessments (FAO, 2015d) have underlined the fact that there are still major gaps in the breeds that are covered by conservation programmes, especially in developing regions, and particularly for ex situ in vitro conservation programmes.

Climate change, which is expected to test the resilience of livestock systems, may constitute a major threat to the most vulnerable breeds and require the strengthening of conservation measures. Cryopreservation of semen and embryos from vulnerable breeds would allow for the reconstitution of breeds that may suffer severe declines in numbers from catastrophic events. It would also increase the availability of germplasm that could be used to facilitate the introduction of traits associated with improved adaptation to new environmental conditions. However, to realize these potential benefits would require the storage of sufficient amounts of material, the adequate characterization of phenotypes relative to environmental features, and significant improvements in breed coverage for ex situ conservation. In addition to the usual goals of maintaining or increasing population sizes, controlling inbreeding and improving profitability, in situ conservation programmes would have to consider climate change adaptation among their objectives.