With summer upon us and the expectation of (at least some) sunshine and higher temperatures, this article serves as a timely reminder of prevention is better than cure for heat stress in all classes of pig.

Dr Lorraine Salmon

Effects of Heat stress

Heat stress is when the animals cooling mechanisms are impaired and results in a redistribution of blood to the outside of the body to aid evaporative cooling close to the skin surface. What follows is a reduction in the blood supply and oxygen (ischemia) to the gut which results in damage to cells lining the gut (leaky gut) and letting endotoxins and other harmful compounds to enter the body.

When blood supply resumes (reperfusion), reactive oxygen species and cytokines are released, causing multiple organ damage especially the liver and stimulating the immune system.

The damage to the liver affects gluconeogenesis (glucose production), causes fatty liver and could also reduce production of anabolic hormones. It’s the stimulation of the immune system that reduces appetite, produces fever and lethargy and finally, reduces productivity.

For sows, seasonal infertility, lower farrowing rates and a reduction in litter numbers/performance is not new, but recent scientific papers have suggested that the future performance of in-utero piglets are affected too.

Prof Baumgard, the author, suggests the damage caused by heat stress alters nutrient partitioning and altered tissue growth in growing pigs with more of the nutrients partitioned towards fat and less to lean tissue. The impact of the altered tissue growth in growing finishing pigs could give rise to a reduction in carcass quality and fatter carcasses, as well as an increased FCR resulting in a higher feed cost per kg gain.

With in-utero heat stress being an underappreciated constraint and combined with post-natal heat stress, Prof Baumgard proposes that together, these create an economic burden that dwarfs most other issues.

Whilst there are nutritional strategies that can help ameliorate heat stress and the subsequent leaky gut, eg. feed additives such as betaine and organic zinc, the primary goal is to prevent or at least limit the level and length of the heat stress suffered by the pig.

Indoor pig buildings will rely on airflow and water supply to manage temperatures. Check fans and air vents are clean and working to their full capacity.

Whilst outdoor pig environments are more difficult to control, the use of shades and pig wallows will help with cooling. For both indoor and outdoor pigs, check drinkers are clear and have the correct water pressure for the age of pig and any troughs are cleaned out daily of stones/straw.

Feed additives such as zinc, live yeast and acids can help reduce the endotoxin burden by managing the levels of gut bacteria, whilst compounds such as betaine can improve the ability of gut cells to cope with damaging osmotic challenges of heat stress.

If you would like to discuss management and the best nutritional strategy for your unit to manage heat stress, please contact your nutritionist at Premier who will be happy to help.