Heat stress in pigs puts an economic strain on pig production in many countries of the world and the current climate changes have increased the prevalence and intensity of heat stress. Nutritional interventions supporting resilience mechanisms represent a practical, adaptable and cost-effective strategy to mitigate the negative effects of heat stress and improve animal productivity.
Economic losses from heat stress in pigs
Compared to other animals, pigs are more sensitive to heat stress due to their high metabolic heat production, quick fat deposition, and lack of sweat glands. Heat stress-induced economic losses result from reduced and inconsistent growth, poor sow performance and increased mortality and morbidity. In the US alone heat stress is costing pig farmers around $50 to $60 per pig each year. Regions around the world most affected by climate change are likely to see an increase in the detrimental effects of heat stress on animal production and welfare in the future. On top of that genetic selection for increased litter size and leaner phenotypes leads to an increase in thermal sensitivity in pigs, due to increased basal heat production.
Summer heat stress in sows
Sows suffer from heat stress in environmental temperatures above 25°C. Heat stress in sows has been shown to reduce feed intake, from 655 g/day to more than 2 kg per day, with subsequent negative consequences for reproduction, milk production and piglet growth. If the sow is maintained under heat stress conditions for a long period, there is a risk that the animal will overheat, which can lead to death via hyperthermia. In countries with tropical conditions such as Brazil this is very common. According to researchers in Brazil, lactating sows of some genetic lines can have up to 15% mortality during Brazilian summers due to heat stress conditions. In gestating sows there is some evidence that heat stress during pregnancy can have in utero negative effects on the offspring’s thermoregulatory capabilities.
Heat stress in fattening pigs
Research has shown that it only takes 2-6 hours of heat stress (37C and 40% humidity) to compromise feed intake and intestinal integrity in growing pigs. Studies in finishing pigs have also shown oxidative stress in the liver in response to chronic heat stress at 30 °C. The drop in feed intake in response to heat stress increases as the body weight increases in pigs. Pigs of 60-100kg raised in Brazil during the summer months have been reported to have a reduction in growth rates of around 15% compared to pigs raised during the winter.
Management interventions for heat stress in pigs
Flexible, affordable management approaches to immediately decrease heat stress susceptibility without negatively influencing traditional production traits are of great value to pig production. However, the input cost for optimal cooling technology is very costly and often too expensive for smaller producers.
Dietary supplementation and modifications are less costly easily adjustable tactics and are suitable for all production systems.
• Consider the thermal effect of feed and reduce fibres and crude proteins, which generate a lot of heat.
• Increase the fat content of the diet
• Feed pigs during the cooler hours of the day
• Provide pigs with unlimited access to cool and fresh drinking water
• Adapt vitamin, mineral and amino acid levels in feed to the pig requirements under heat stress
Supporting resilience mechanisms by nutritional means
Research increasing the understanding of the molecular mechanisms involved in heat stress induced inflammation and intestinal barrier disruption paves the way to nutritional strategies to preserve the physiological performance of the gut. Many of the negative consequences that heat stress has on pig health and productivity are mediated by reduced intestinal barrier integrity, which is followed by inflammatory responses.
At the cellular level, hyperthermia leads to disruption of intestinal epithelial integrity, by affecting tight junctions. Damage to tight junctions facilitates the transfer of toxins and pathogens from the gut through the epithelial barrier, contributing to an exaggeration of inflammatory responses, which can further worsen the intestinal damage. Hyperthermia provokes the production of reactive oxygen species (ROS). However, it can also directly impair the antioxidant defence system of the animal, which eventually leads to oxidative stress and intracellular damage. Studies in growing pigs have shown an inverse relationship between oxidative status and growth performance, whereby pigs with a higher oxidative stress status had poorer performance.
Nutritional solutions which have the capacity to preserve cellular homeostasis by enhancing cellular defense systems, as well as maintain intestinal integrity are considered to be able to help protect animals against the adverse effects of heat stress.
Gut agility activators are feed supplements that were specifically formulated to enhance the resilience of animals, by supporting cellular defense systems and enabling more efficient responses to stressors thus mitigating the impact on performance.
Sow trial with Anco FIT during summer months
A recent sow lactation trial carried out in the summer months in Argentina, showed increased feed intake (21%) and improved lactation performance in sows fed the gut agility activator Anco FIT compared to sows on a control diet.