Be aware: Summer months can lead to heat stress

Heat stress in pigs can lead to production losses and even death, but can be managed through sound husbandry.

pig drinking water in group pen

Like all animals, pigs are periodically exposed to conditions that cause stress. During the summer months, it is especially important to be observant of the pigs’ condition and consistently watch for signs of heat stress, which is estimated to cost U.S. pork producers more than $300 million each year. Heat stress in pigs typically occurs during extended periods of high air temperature, made worse by high humidity. Pigs are unable to adjust to extreme heat the way other animals do because they are unable to sweat and lose heat through evaporation, and the small volume of their lungs makes panting inefficient. Pigs weighing over 75 kg are more susceptible to heat stress than smaller animals because their subcutaneous fat prevents heat loss through conduction and convection. If left unchecked, over-heating in pigs can be accompanied by changes in gut permeability which may lead to water loss/dehydration, infection, fever and in some cases, death (Gabler and Pearce, 2015).  

Typical clinical signs of heat stress in pigs include rapid open-mouth breathing (panting), blotchy skin, reduced eating and movement and muscle tremors. The impacts of heat stress can be reduced by several measures, including reducing stocking density, increasing airflow by using fans, providing shade and cool water to drink (at least one water nipple per 10 pigs, with a flow rate of one quart per minute) and spraying or misting with cool water. Adding electrolytes to water might encourage animals to drink more, which is beneficial during hot periods. It is important to conduct a thorough check of your ventilation system before things get too hot. Recent research by Johnson (2017) showed that an 11 percent reduction in airflow in the pen led to a 0.42° Fahrenheit increase in body temperature and a 6 percent reduction in pig growth efficiency. It is also helpful to schedule feeding and pen checks for cooler times of the day, as movement associated with feeding generates body heat that dissipates more rapidly during cooler periods. 

For animals ready to market, transporting during cooler hours of the day is helpful. Although withdrawing feed for 12 to 18 hours prior to slaughter enhances pork safety, meat quality and animal well-being while reducing incidence of PSE pork and in-transit loss, drinking water should be available to pigs whenever possible, especially when air temperature and humidity are high (Bidner and McKeith, 1998). If animals are transported long distances in hot weather, it might also help to use a moderate or light amount of bedding (and avoid straw, which holds heat) on trailers, as body temperatures can rise dramatically when animals are packed together (McGlone et al, 2014, and see the TQA Handbook, Weather Conditions section). 

For additional information regarding management strategies for pigs during hot weather, see: Management strategies to improve finishing pig performance during hot weather.

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