We, humans, cope quite well. We have a warm dry house, waterproof clothing, we can change our clothes and most importantly turn the heat up in our house or place a fan on to cool down.
In Summer our pigs do suffer from the heat and this we may have observed and experienced by certain behaviours.
Suffering the heat, effects their eating habits by a decreased feed intake which in turn is compounded by slow growth and milk production, but we often fail to realise that younger pigs suffer equally or to a greater extent during the cooler times of the year. Harmful results of chilling include slower growth, poor feed efficiency, loss of body fat, greater susceptibility to diseases such as scours and pneumonia, higher mortality and even an increase in aggression.
When conditions are too cold, the pig will attempt to adapt by increasing heat production within its body and by minimising heat loss. Shivering increases metabolic heat production, and increasing feed intake increases heat production from digestion of feedstuffs which helps make the pig feel warmer, yes it is common sense but sometimes there is always one that will slip us by. It is also true to say, when pigs are stressed, they eat less rather than more so their heat production actually decreases. This is especially true at weaning time and when weaners are bought/sold and taken to their new homes in the winter or spring.
Common sense prevails and it may not surprise you that great care must be taken to keep them warm during transport and for at least 1-2 weeks after they arrive.
Particular mannerisms to look out for when our pigs are trying to minimise heat loss include: huddling together, tucking their legs beneath their bodies to limit contact with the floor and seeking shelter or the warmest, least drafty area in their pen. You may observe that the younger pigs may even alter their dunging and sleeping habits and lie down in their excrement because faeces and urine provide a temporarily warm floor. But, in the long run, this behaviour gets them wet, increases heat loss from their body and just makes them feel even colder.
Lower Critical Temperature is the temperature below which a pig must expend additional energy to maintain normal body temperature and essential body functions such as eating, drinking, playing and moving about.
The Upper Critical Temperature is that which adversely effects pig performance and normal bodily functions including decreased feed intake and rate of gain due to heat stress. The range
This is especially true for the Lower Critical Temperature, which is much higher for younger pigs than older ones. Young pigs up to 18-22kgs are very sensitive to low temperatures and become chilled quickly. On the other hand, finishing pigs and lactating sows are much less sensitive to cold but do not tolerate high environmental temperatures, 2019 was testament to that as there was many losses due to the hot summer we had due to heat stress.between the both is called the Thermo- neutral Zone or Comfort Zone. The Comfort Zone varies by the age and size of our pigs with larger pigs generally tolerating extremes in temperature.
As mentioned in previous dialogues, the temperature that pigs feel is seldom the same as what we read on a thermometer or that we as humans feel in the same environment. The temperature that the pig feels is called EffectiveTemperature. First of all, it is critical that we measure temperature at pig level since that may differ several degrees from a reading made at eye level on the wall several feet away from the pigs. For nursery pigs, this would be at a height of about 8-12 inches inside the animals’ pen. Even if measured properly, the reading on the thermometer is probably not the temperature that the pigs feel because there are several factors in addition to age and size that influence EffectiveTemperature. Therefore, the animal may not be comfortable and productive even if the temperature on the thermometer is within its Comfort Zone.
EffectiveTemperature is influenced by losses of heat from the body in at least four different ways.
Air moving across the animal’s body due to drafts, poorly designed or improperly managed ventilation or use of open-sided shelters for young pigs in autumn, winter and spring.
Radiant losses to cold surfaces such as poorly insulated walls, and ceilings, even though the animal is not touching the surface. An analogy of this is the feeling you get when you sit beside a single pane glass door in winter time as compared to sitting beside a heavily insulated wall. Your body heat is being used to warm that glass door.
Convective losses to surfaces the animal actually touches, especially floors. Concrete and metal floors are much “colder” than plastic, rubber mats or wood. Pigs lose half as much heat to a wooden floor as to concrete and only one-sixth as much to a plastic floor. However, wood is impossible to clean and disinfect so it is not recommended as a permanent flooring material in indoor production. Slatted floors are much colder than solid ones, regardless of material.
Evaporative loss of heat from the surface of the pig’s body occurs whenever our pig gets wet. Evaporation of water from the skin takes heat with it. We experience this when we exit the bath or shower and step into a cold room. Examples include accidentally spraying pigs while washing down facilities, pigs lying in their own faeces and urine, wet floors from leaking water vessels or using water to clean pens. However, we do use some of these methods when weaners/sows/boars need to keep cool in summer ie; spraying or hosing down our pigs.
How much do these losses of heat influence the way the environment feels to the pig; i.e., the Effective Temperature? For example, a slight draft of 40 ft/minute feels chilly to a 3-4 week old pig and makes an 26º room feel like 22º. This minimal draft is often not even detectable by people. A draft of 100 ft./minute will make that same room feel like 19º. Poor insulation in walls and ceilings and wet, cold floors will drop the Effective Temperature by 7º with each circumstance.
Therefore in a room where the thermometer at pig level reads 26º but there is a slight draft (-7º) and the concrete floors are wet (-7º), the pigs will feel like its 18º. Lack of insulation will drop Effective Temperature another 7º to 15ºC.
But as we know, providing a deep, dry straw bed will increase effective temperature by 8-12º. Therefore, pigs in a pen at 21º will feel more like 26º. As a general guide, dry straw bedding will make up for most of the wet and wintery months and the harmful effects of cold, wet floors and lack of insulation. However, drafts can still be a major problem, especially for 13-22kgs pigs in winter or spring when night temperatures can still be a little chilly, even if a deep straw bed is provided. At best, even with no drafts, the effective temperature will be 12-18º and pigs will feel chilled and probably get sick. Most other types of bedding, including shavings, are not nearly as effective as clean, dry straw. Ground or finely chopped straw is also less effective than “long” straw.
We know that older/heavier pigs are more resistant to cold and less resistant to heat and we, therefore, are more concerned with their comfort and well-being in the summer. Younger/lighter pigs up to about 8 weeks of age or 50 lbs can tolerate heat but are extremely sensitive to cold.
Since cold stress can be very harmful to the health and productivity of young pigs, what can be done to minimize it and make these smaller pigs as comfortable as possible? The following list is not exhaustive but includes some of the most important steps for pigs from birth to 22 kgs.
Learn how to identify cold-stressed pigs. Shivering pigs huddled together or lying with their feet tucked beneath them are sure signs of discomfort. Many of these pigs will get..
skinny and develop long rough hair coats (which we have seen from time to time. It is not a critisim of the breeder) if the cold stress continues for more than a few days.
Keep pigs dry at all times and replace or add new dry bedding frequently.
Eliminate drafts. Decrease ventilation during the cooler months, plug holes in walls and ceilings, replace broken roof profiles or windows. Use solid pen dividers. Never leave doors or windows open.
Add insulation to walls and ceilings.
A few ideas to prevent heat loss and maintain the minimum Effective Temperature, is create a micro-environment. Combine zone heating areas such as heat lamps or creep boxes and/or kennel-type rearing pens.
“Whats in your barn Video” which can be seen in our video files on our facebook page. Features common to all three are lids or covers, solid floors, and they are made of “warm materials.” Do not use steel, aluminum or concrete.
Limit multiple stressors. Do not wean, vaccinate, change feed, transport, change environment and mix pigs on the same day. Doing more than two of them simultaneously will make the pigs more susceptible to chilling and health problems such as scour (diarrhoea).
Examples of good practices to limit stress
At weaning, just remove the sow and leave the pigs where they are for 1-3 days.
Make sure tagging, notching and tattooing and vaccinations are done well before weaning or transport.
When purchasing weaners/breeding gilts/sows and boars, bring them home and put them in an light, clean environment. Do not change feed, mix pigs or impose any other management stressors for about a week.