The effect of temperature on sow performance


Keep them cool. Although we experience different climates all over the world, in general high temperatures and humidity give all sows a challenge, especially during lactation. This impact of higher temperatures and humidity on sow performance is better known as heat stress. Heat stress in lactating sows has been shown to lead to a reduction in feed intake, milk production, reproductive performance, and indirectly to the growth rate of piglets. In fact these adverse effects can already occur when ambient temperatures rise above the 23-25 °C.

So, what is happening and how can we support the sow to minimize loss of performance?

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High temperatures and humidity – what is happening?

Young piglets drinking sow milk at the sow.

Heat stress in pigs occurs when ambient temperatures rise above the thermoneutral zone of the pig and the animal’s body cannot get rid of the excess body heat. Pigs, unlike some other animals, do not have functional sweat glands. In this way they are not able to sweat and to get rid of their body heat efficiently. This means that when ambient temperatures rise, a sows’ body temperature is also likely to rise.

For a lactating sow, the optimal ambient temperature is below 20 °C. When temperatures rise above 23-25 degrees, heat stress can already occur. Next to the ambient temperature, relative humidity also influences this (upper) temperature, meaning that, with higher humidity, heat stress in lactating sows can already occur at lower ambient temperatures.

When sows are exposed to heat stress, they adapt their behavior to lose (more) body heat. One of these behaviors is that they start panting and that their feed intake also decreases because their feed intake and the digestion of feed will contribute to further heat production in the sows’ body. A meta-analysis performed by Ribeiro et al. (2018; based on 20 scientific articles) to evaluate the effect of heat on the performance of lactating sows and their litters showed that, for each degree of increase in ambient temperature, there was a mean feed intake reduction of 148 g/d (see figure). Research by Renaudeau et al. (2003) also showed that each increase of one degree in the ambient temperature between 25 °C and 27 °C, with humidity ranging between 50% and 60%, caused a feed intake reduction of 214 g/d.

Figure. Graphic representation of the model used to calculate feed intake, piglet weight at 21 days, and milk production in relation to the variation in ambient temperature. The comparisons resulted in a predictive value (R2) of 78.68%, 93.37% and 87.50% for feed intake, milk production and the weaning weight of the piglets respectively (Ribeiro et al., 2018).

Milk production is (mainly) affected by feed intake with, as a result, that heat stress also highly negatively affects the milk production. With each degree increase in ambient temperature, a 227  g/d reduction in the sows’ milk production could be seen (Ribeiro et al., 2018). This has indirectly adverse consequences for the performance of the piglets.

What can you do to support your sows?

In order to minimize loss of performance and eventually profit, here are three important but sometimes overlooked tips.

1. Feed sows smaller, but more frequent, meals during the day and feed during the coolest parts of the day.

Next to feed, also make sure that the sow has access to (extra) water. This is true especially before and after farrowing, in order to optimally initiate milk production and improve feed intake. Hygiene is also an important topic to pay attention to as higher temperatures increase the risk of spoiling the feed provided to the animals. Make sure to keep the feed fresh in order to increase feed intake.

To stimulate feed intake, fresh air could also be provided at the head of the sow. The fresh air results in the sow’s perceived temperature going down which makes her better able to evaporate water in the lungs and to consume feed.

2. Alter the nutritional balance of the diet.

The performance of lactating sows exposed to high temperatures can be improved by reducing the animal’s heat production by, for instance, lowering the crude protein level or using less fiber. You should also replace starch with fat as an energy source. Fat is an excellent source of energy and an ingredient that generates less heat during digestion. However, make sure to feed a palatable and good digestible fat source, like the type of fat used in Lactolat.

Lactolat is a dairy based ingredient especially designed for sows during lactation and contains active ingredients to stimulate appetite and improve feed intake, as well as micro-encapsulated fat based on coconut and palm oil.

3. Support the piglets.

The decrease in feed intake of the sow during lactation due to heat stress has a negative impact on milk production. It is therefore important to support the piglets during lactation by feeding them additional milk, like Porcolac.

Porcolac is a premium milk replacer, packed with the right nutrients from dairy products and supplemented with essentials vitamins, minerals and our Imagro health concept. In this way, the sows are supported in fulfilling the needs of the piglets, not at the expense of the milk yield of the sow, and the piglets also benefit from the extra nutrients and energy provided by the milk replacer.

Would you like to know more about our products for supporting sows and piglets?

Contact our Animal Nutrition team via for more information and support.

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