54. Pigs subjected to excessively high temperatures are likely to suffer heat stress. When a pig's body temperature rises beyond its normal limits the animal becomes heat stressed. The first sign is panting and, if the body temperature continues to rise, the pig collapses and may die. Heat stress not only causes suffering but it also reduces productivity and affects fertility. It can lower the feed intake of lactating sows thereby reducing their milk production and culminating in adverse effects on their piglets. It is essential that pigs are provided with sufficient water, both for drinking and in wallows, during periods of high temperature (see paragraphs 123 and 124).
55. Farrowing huts can become very hot in summer, so it is important to keep the interior as cool as possible in order to encourage the sows to remain with their piglets. This may be achieved by using an adjustable ventilation opening at the rear of the hut and/or insulation to reduce solar heat gain. The greatest benefits of insulation in farrowing huts are likely to be seen in hot weather.
56. Pig breeds vary in their susceptibility to sunburn which can pose a major welfare problem if suitable precautions, such as the provision of wallows and shade, are not taken. Traditionally wallows are constructed in the paddocks using water from a bowser, overflowing water trough or water jet. On certain soils, and where sows have nose-rings, it may be necessary for a hole to be dug by the stockman. The provision of a suitably muddy wallow improves evaporative heat loss and provides a durable layer of mud on the body which will protect the pig from sunburn for a period after wallowing. However, there is a potential danger in the farrowing paddock as the sow may spend excessive periods in a wallow and leave her piglets unattended for so long that they suffer or even die. It is therefore extremely important to keep the inside of the farrowing hut as cool as possible so that there is no disincentive in returning to it.
57. Information about the avoidance of heat stress is contained in a MAFF publication Heat Stress in Pigs - Solving the Problem which is available free from MAFF Publications, London, SE99 7TP (tel: 0645 556000) - quote ref PB 1316.