Cold Temperature Management for Pigs

As a pig producer, managing heat loss during winter months can be a struggle for the health of your pigs and your profits, particularly for pigs that are housed predominantly outside or in unheated shelters. Pigs that are struggling to stay warm commonly experience cold-stress-induced health problems, reduced growth rates, and poor reproductive performance.

Historically, pig production was seasonal due to the high cost of keeping pigs warm. However, some producers may wish to take advantage of the slow season at your local packer, which means raising pigs to slaughter through the winter. Investing in proper housing can keep your pigs growing quickly and keep feed bills to a minimum. Producers who choose to raise swine over the winter may also be managing a reproductive herd. If you are breeding sows during the winter months and housing them outdoors, investment in proper housing can improve the reproductive performance of your herd.

Cold Stress Index

Temperature stress occurs when pigs fall outside their thermal neutral zone. This 'zone' is an environmental temperature range that allows the pig to prioritize feed nutrients for building meat or reproductive tissues, rather than struggling to maintain body temperature. For pigs, this thermal neutral zone is notably narrow. What does this mean? This means that pigs have a limited range of temperatures that allow them to optimally prioritize nutrients for growth or reproduction; temperatures outside this range often result in some form of stress for the pig. Pigs can experience heat stress if housed persistently in temperatures above the thermal neutral zone. Similarly, pigs housed at temperatures persistently below the thermal neutral zone are at risk of cold stress. But what does stress, particularly cold stress, look like in a pig production setting? Predominantly, it means reduced feed efficiency, reduced or stunted growth rates, or weight loss.

Cold Pigs are High Maintenance, Literally

Cold pigs, even mature pigs, require more feed to maintain heat production and body condition. Growing pigs living in cold conditions will have poor feed conversion rates, increased feed intake, and will likely struggle to grow without free access to good feed and housing to keep warm. How much feed does it take to maintain body weight or growth in cold temperatures? Depending on the pig's age and size, and on outside temperatures and weather conditions, you may need to increase the daily feed allowance by 3x or more.

Calories, energy to produce heat and stay alive, cannot realistically be met by simply increasing feed as the surrounding temperature decreases. Increasing the energy density of the diet also has limitations on its impact on pig growth in persistent cold. Why? Pigs are limited in their ability to eat massive amounts of calories in a given day. Essentially, when temperatures are too cold and are persistent (lasting several days to weeks), pigs often find themselves in a negative energy balance that cannot be corrected with feed alone. This leads to slowed or stunted growth of young pigs and weight loss in older pigs. Young pigs that grow slowly will continue to physiologically mature but not maximize muscle growth before maturing into stages of fat deposition. In the most extreme cases, this can result in death. Cold stress creates a poor welfare situation for your pigs, as it is an unnecessary burden that challenges their growth capacity, immune system, and even their ability to live.

What does slow growth and increased feed mean? This means more feed for less meat; for your business, it means higher input costs (feed, housing) and lower returns (price per pig for meat yield).

In the Northeastern United States, cold spells are becoming more extreme. This emphasizes the importance of appropriate housing for pigs during winter, as they have limited ability to meet their body heat needs solely through diet.

How Cold is Too Cold?

For swine, tolerance of cold temperatures is dependent on numerous factors.

• Primarily, pigs should be offered shelter from precipitation and dampness. Water conducts heat. Humidity in the air will be drawn to your pigs, pulling heat from them. Regardless of flooring type or usage of bedding material, all efforts should be made to provide pigs with a dry bedding area.
• Provide wind breaks and shelter from drafts. When providing shelter, be sure your wind breaks do not allow air to draft around the space at pig level.
• Insulate the pig area. This can take many forms, from bedding to insulated walls and ceilings. The idea is to capture as much of the pigs' heat as possible, while still allowing air exchange. More information on winter swine housing can be found in the Winter Housing for Swine Welfare article found on Penn State Extension's website.
• Strive to keep ambient temperatures within the thermoneutral (TN) zone of the pig, for age and body size. The thermoneutral zone for most mammals varies with age and body weight. For suckling and young growing pigs, this is particularly important, as they lack significant adipose (fat) stores at birth and do not develop these stores until maturity. This lack of fat prevents them from having any energy reserves to maintain body heat. Approximate thermoneutral zone temperatures are provided in the table below.

(Adapted from Effect of Environment on Nutrient Requirements of Domestic Animals).

• Keep mature pigs in good body condition score. Maintaining a healthy fat cover in mature pigs (~6 months or older) can serve as both an insulator and an additional energy reserve for generating body heat. Routinely scoring your pigs' body condition can help you determine whether they are getting enough to eat and how they are handling winter temperatures. Pigs with a poor body condition score will struggle more with cold temperatures than pigs with a healthy body condition score. 

These tips for managing your pigs' environment can help you improve winter conditions, meet their needs, and keep costs in check. As you prep your pigs for the winter cold, please reach out to Penn State Extension for more tips and information on addressing cold weather for your swine herd.