Overview of climate change impacts on animal agriculture in the Southwestern United States
Animal agriculture accounts for one-third of the agricultural revenue in the Southwest. In 2012, the market value of livestock and poultry for the six-state region was $17.6 billion. Approximately 70% of Southwest livestock revenues are from dairy cows, cattle and calves. Unlike poultry and swine, which are often housed in structures, cattle, goats and sheep are typically subject to outdoor conditions and susceptible to the elevated temperatures of a changing climate.
There are four primary ways in which climate change will affect animal agriculture in the Southwest. Those pathways, outlined in the National Climate Assessment, are:
- feed-grain production, availability, and price;
- pastures and forage crop production and quality;
- animal health, growth, and reproduction; and
- disease and pest distributions
Feed-grain production, availability and price are directly linked to the higher temperatures and reduced regional precipitation discussed previously. In the Southwest, elevated temperatures and increased water scarcity will negatively impact feed-grain production and quality.
In the Southwest, livestock production will be reduced by lower forage quality and quantity and a decrease in voluntary animal intake associated with lower forage quality, higher temperatures, and heat stress (Polley et al. 2013).
Animal health, growth, and reproduction are adversely impacted by elevated temperatures. Elevated humidity exaggerates temperature impacts necessitating the use of a metric accounting for both factors, such as the temperature humidity index. Heat stress factors vary by species, stage of production, genetics, animal health status, and the acclimation period. Other weather related heat stress factors include event duration and night cooling period. The total annual economic losses from heat stress in dairy cows in Arizona, California, New Mexico, Nevada, and Utah is estimated to be $168.7 M per year (St-Pierre et al. 2003).
Direct impacts on animals from high temperatures include catastrophic death loss, reduced feeding efficiency, reduced growth rate, and increased illness. Optimum animal core body temperature is often maintained within a 4°F to 5°F range. In many species, deviations in core body temperature in excess of 4°F to 5°F cause significant reductions in reproductive success, while deviations of 9°F to 12.6°F often result in death.
Livestock and dairy production are more affected by the number of days of extreme heat than by increases in average temperature. In the Southwest, there is high confidence that heat waves will increase in frequency, duration, intensity, and area (Garfin et al. 2014). Exposure to multiple hot nights increases the degree of stress imposed on animals resulting in reduced meat, milk, and egg production.
Animals can typically adapt to and cope with gradual thermal changes. Lack of prior conditioning to rapidly changing temperatures can result in loss of productivity or death in domestic livestock. Along with the stress of extreme heat events, some animals are managed for a high rate of weight gain. This increases their potential risk when exposed to high temperature conditions (Hatfield et al. 2014).
In general, poultry and swine are managed in housed systems where airflow and housing temperature can be controlled to minimize adverse conditions. However, management and energy costs associated with increased temperature regulation will increase for indoor production enterprises under the increased temperatures of the Southwest.
In the Southwest, outbreaks of certain livestock diseases may increase in prevalence due to the temperature and precipitation shifts of a changing climate (Baylis and Githeko 2010). Anthrax outbreaks are often associated with alternating heavy rainfall, drought, and high temperatures, all predicted in increasing prevalence in coming decades. Blackleg, an infectious disease of young cattle, is also associated with high temperature and heavy rainfall. Many other infectious diseases affecting livestock survive best in humid conditions, which will likely decrease in coming decades throughout the Southwest region.