Why climate change is a threat to livestock production

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South Africa’s farmers have little choice: they must adapt in order to limit the effects of climate change on livestock production and animal health, according to experts.

climate-change-sheep
While certain sheep species can withstand high temperatures, extreme heatwaves will have a negative impact on production. According to industry experts, farmers must ensure that sheep have access to shade.
Photo: Glenneis Kriel

Climate change will result in a 1% to 2% increase in the average temperature along coastal areas in South Africa, and a 2% to 3% increase in interior regions by 2050.

This is according to the Green Paper on the National Climate Change Response. To continue producing food, farmers will have to contend with drier climatic conditions, faster evaporation and more frequent incidences of extreme weather such as floods and droughts.

Animal nutrition
Forecasters have predicted that climate change will have a major impact on the quality and quantity of forage crops. Warmer temperatures could result in the deterioration of pasture quality and quantity, making it more difficult for farmers to align production with their animals’ nutritional requirements.

Dr Danie Odendaal, director of the Veterinary Network (V-Net), says that producers will have to better synchronise breeding seasons with nature.

“Look at wild species such as impalas. They reproduce within two to three weeks of each other. This synchronisation has occurred naturally to match the availability of natural veld with their feeding requirements.”

Immunity
Climate change will also affect animals’ immunity. Dr Faffa Malan, CEO of the Ruminant Veterinary Association of South Africa, explains that unfavourable climatic conditions and food scarcity cause stress, which has a negative impact on immunity.

“Many of the breeds we farm in South Africa are not fully adapted to the warm climatic conditions of our country. These animals will struggle even more under warmer temperatures,” he says.

The recent drought was an example of how extreme climatic conditions affected animals, he adds. There was an increase in incidences of all types of infections, particularly lung infections, due to dusty farm conditions. Moreover, lack of sufficient grazing resulted in many animals suffering from energy, protein, phosphate and calcium deficiencies, which led to poor conception rates, retained afterbirths, poor quality colostrum and immunodeficiences.

“Animals that are stressed try to protect themselves by not reproducing,” Malan explains.

Many animals also suffered micronutrient deficiencies, with vitamin A deficiencies particularly common. Vitamin A is crucial for the maintenance of the epithelial tissue, which protects the eyes, and lines the skin and the gastrointestinal, respiratory, urinary and reproductive tracts. Vitamin A deficiencies result in reduced food intake, slowed growth, diarrhoea, excess tearing, blindness and increased vulnerability to infections.

Rainfall and Vector-borne diseases
Climate change is also likely to have an impact on livestock pests and diseases. According to Malan, the introduction of game species to livestock farms and the increased migration of animals as a result of warmer and drier climatic conditions have resulted in diseases such as brucellosis and Asiatic red water appearing in regions where they were previously unknown.

Malan therefore urges farmers to be vigilant about biosecurity.

Prof Koos Coetzer, emeritus professor at the Faculty of Veterinary Science at the University of Pretoria, predicts that the higher-than-average rainfall will coincide with more incidences of vector-borne diseases.

“Back in 1974, widespread flooding occurred in Namibia, Zimbabwe, Botswana and South Africa. The Karoo looked like one big swamp, and vector-borne disease outbreaks occurred throughout the region. I witnessed the same thing around 1998 in East Africa.”

Vector-borne diseases are broadly classified in two categories: arboviral diseases, which are primarily transmitted by mosquitoes, midges or biting flies, and tick-borne diseases, which are transmitted by different tick species.

The viral disease, Rift Valley fever, which is primarily transmitted by mosquitoes, is one of the vector-borne diseases that occur more frequently in Africa as a result of climate change, according to Coetzer.

Rift Valley fever often follows heavy rains and floods, and does not usually occur when conditions are unfavourable.

“Farmers might think the virus is no longer on their farms due to the dry climatic conditions, and may stop vaccinating their animals. Then, when heavy rain occurs, particularly in late summer and autumn, severe outbreaks follow, resulting in severe losses. Vaccines may not be available due to a sudden increase in demand,” Coetzer explains.

Incidences of lumpy skin disease, which is transmitted by biting flies and ticks, may also increase. This disease can cause severe economic loss through damage to hides, decline in production and reproduction, and the death of infected animals.

“We’ve found that severe lumpy skin disease outbreaks usually occur during very wet seasons,” Coetzer says.

Diseases transmitted by midges, such as bluetongue and African horse sickness, may also become more prevalent.

Hot weather, combined with rainfall, often results in a larger tick population and an increased incidence of tick-borne diseases such as African and Asiatic red water, heartwater and anaplasmosis.

“We fear that climate change and, in particular, protracted droughts, might have a negative impact on the endemic stability
of certain tick-borne diseases, due to reduced exposure to ticks. Young animals usually become resistant to certain tick-borne diseases through early exposure to the infection, or due to maternal immunity or age resistance. Without such exposure, animals may become more susceptible and develop the disease when challenged,” he explains.

Prevention
Coetzer stresses that prevention is key and the necessity for good biosecurity and frequent vaccinations cannot be overstated.

Managing and controlling disease vectors can also help prevent the transmission of these diseases to livestock. High-value animals, such as horses, can be stalled, and repellents used to protect them from midges at times when the risk of African horse sickness is high.

Tick numbers should also be controlled. As the resistance of ticks to certain treatments is increasing, farmers should apply treatment as per product recommendations.

Knowing one’s farm’s vulnerabilities to specific conditions that may trigger these diseases, as well as having a good relationship with a veterinarian, are useful in early detection and prevention.

Odendaal says that V-Net’s primary objective is to prevent the spread of these diseases.

“There are 130 veterinarians across the country who belong to the veterinary network, each with about 150 clients. The first objective of this network is to give clients timeous reminders of actions that should be taken during specific times of the year to prevent specific disease risks.”

V-Net’s second objective is to inform farmers about potential threats. “For example, we inform clients that it’s dry and that the feed situation might become problematic, or we let our clients know that there’s a disease in the region that has not been detected there before.

“Our third objective is to warn farmers and producers of specific dangers. For example, we warn them about rabies or brucellosis outbreaks.”

Email Dr Danie Odendaal at [email protected].