With summer months fast approaching and growing concerns about extreme weather events, livestock experts are warning farmers against the effects of heat stress on their animals. It is not always fatal but can also affect animal production.
Heat stress is caused by high air temperatures, radiant heat sources, high humidity, direct physical contact with hot objects and strenuous physical activities, and has made headlines in the past even for its effects on wildlife. In November 2020 at least 110 birds and fruit bats succumbed to heat stress at the Phongolo Nature Reserve in northern KwaZulu-Natal.
Animal experts say that apart from causing death, heat stress can create metabolic disruptions, oxidative stress and immune suppression, which causes infections in animals.
Dr Mpho Maja, director of animal health at the department of agriculture, land reform and rural development, says that heat-related stress due to high temperatures and humidity occurs when animals are no longer capable of naturally eliminating excess body heat. It is important for farmers to monitor animals at this time to make sure they remain cool, healthy and safe.
“There are several visible signs associated with heat stress in animals, including increased effort to breathe or difficulty breathing, excessive panting, drooling, bright red gums, anxious behaviour, excessive water consumption, vomiting or diarrhoea, weakness, dazed expressions or incoherent behaviour and collapse or seizure.”
ALSO READ: Deadly disease to hit livestock as early as February
Heat stress in dairy cows
Liezel Olivier, spokesperson for Olfactum Nutrition, says that in dairy cows, heat stress during gestation has a negative impact on lactation and, therefore, subsequent milk yield. It also impacts fat levels in milk and negatively impacts reproduction and immunity.
“External signs indicating thermal stress are easy to observe in the herd and include an accelerated respiratory rate, open mouth and mucous ptyalism [over-production],” she explains.
According to Olivier equipment such as fans or misting systems are increasingly being used on dairy farms confronted with heat stress. Unfortunately, these tools are not sufficient to preserve the dairy yield potential as there is a double rumen-related impact: lower dry-matter intake and lower feed efficiency.”
“Feed rations must therefore be adjusted during high-risk periods to reduce these impacts,” she warns.
She adds that research is underway to develop ways of ensuring the better-being of farm animals. “Thorough knowledge of the brain’s ecosystems led Phodé to develop a one-of-a-kind plant-based solution, mainly composed of a specific extract from the Rutaceae [citrus plant] family that neuromodulates the signalling stress message in the nervous system. As a result, dairy cows perceive less environmental heat stress and behave normally. In other words, there are fewer changes in feed intake or behaviour.”
Heat stress in beef cattle
According to a report on climate change, the impact it has on livestock and how agriculture can adapt, beef cattle with their lower metabolic rate and lower body heat production, are usually considered less sensitive to heat stress than dairy cattle.
However, beef cattle also compensate for increased body temperature by homeostatic mechanisms (panting, sweating and urination) and behavioural alterations such as reduced activity, increased water intake and reduced feed intake. These effects are responsible for a generally lower growth rate and reduced fertility of both males and females.
Heat stress in pigs
Pigs are more susceptible to heat stress than beef cattle. Globally, pork is one of the most consumed animal-source foods. Reduced and inconsistent growth, decreased feed efficiency, decreased carcass quality, poor sow performance, decreased reproductive performance (male and female), increased mortality (especially in sows and market hogs) and morbidity are the main economic losses associated with heat stress in the swine industry.
Evidence suggests that maternal exposure to heat stress has long-lasting effects on postnatal offspring performance.
Mauritz de Villiers technical advisor at the Pig Improvement Company (PIC), says that when pigs get heat stress, especially in the Western Cape, they just stop their feed intake.
De Villiers adds that this also happens in most livestock when there is extreme heat.
He says that one of their solutions is to feed the pigs less because feed also increases their energy exchange, which can cause heat stress.
Additional approaches, including dietary modifications and genetic improvement, may help improve mitigation and adaptation of pigs to adverse environmental conditions.
ALSO READ: Farmers warned about devastating citrus disease
Sign up for Mzansi Today: Your daily take on the news and happenings from the agriculture value chain.
