Prevent heat stress with feeding

Low birth weights, too little sow milk for all piglets, high weight loss of sows at the end of the suckling period, high turnover rates – these problems often have one cause: an energy deficit in the sows’ ration design, especially at very high outside temperatures.

While the performance level of our sows has risen steadily in recent years, the feed intake capacity of the animals has not kept pace to the same extent. Especially the supply of energy according to demand often proves to be a challenge. Especially at high temperatures, feed intake drops, and the energy gap becomes larger.

Feed intake decreases significantly

For the near future, not only much higher average temperatures are forecast, but also increasingly longer heat waves. With higher outdoor temperatures, the temperatures in the stables usually also rise significantly.

Heat stress has far-reaching consequences, especially for sows. A sow’s thermoneutral zone, i.e. her comfort zone, is already exceeded at a stall temperature of 22 °C. The sow’s feed intake drops by 0.1 kg per day for each degree of temperature increase. From 21 °C, the sow’s feed intake drops by 0.1 kg per day for each degree of temperature increase. This corresponds to an energy quantity of about 0.13 MJ ME. At temperatures around 30 °C, the feed intake is reduced by about 1 kg per day. This means that the sows consume about 13 MJ ME less energy per day.

What happens at high temperatures

The energy deficit results in increased live weight loss, reduced milk production and thus reduced litter growth of the piglets. Further consequences can be the frequent occurrence of MMA diseases and problems with the subsequent rumination. Heavily weaned sows (over 20 kg weight loss in the suckling phase) have a longer gestation period, less pronounced oestrus symptoms, fewer fertilisable eggs and thus a lower number of embryos. The consequences are a lower number of piglets per litter and a longer inter-litter period.

Effect of ambient temperature on feed intake of lactating sows and weaning weight of piglets (Source: Quiniou and Noblet, 1999)

As a result of the high metabolic load on the animals during heat, more free radicals and oxidative stress can also occur. As a result, the intestinal mucosa becomes “leaky gut” and the very important barrier function of the mucosa of the small intestine is disturbed. barrier function of the mucous membrane of the small intestine is disturbed. This paves the way for endotoxins and pathogens and has a negative impact on animal health overall.

More fat in the feed

Oils and fats can play an important role in rations due to their very high energy density. Compared with energy from carbohydrates and crude fibre less heat is released during digestion of fats when they are broken down into fatty acids. Further advantages result from the supply of fat-soluble vitamins and essential fatty acids. Fats also fulfil important biological functions, actively intervene in the metabolism and take on important protective functions.

Since liquid oils can only be used in feed to a limited extent for technical reasons, fat powders are a good alternative. With such powders, higher fat contents can be achieved in the feed than it would be possible with conventional liquid oils. A high nutrient concentration in the feed is particularly important for lactating sows. Their energy requirements are directly related to their milk yield. With a litter size of twelve piglets, the sow produces about 340 kg of milk during a four-week suckling period. Assuming 12 litres of milk per day, the amount of energy required from feed is about 85 MJ ME. To this must be added the sow’s maintenance requirements. Accordingly, the lactation feed should have an energy density over 13 MJ ME/kg so that the animals can produce these 12 litres milk per day, even with reduced feed intake due to heat stress.

In rations with a reduced energy content, for example with less than 12.8 MJ ME/kg, an adequate energy supply is difficult to implement due to the limited feed intake.

More digestible with lecithin

To improve the digestibility of rations enriched with fat, an emulsifier, for example lecithin, can be used. Lecithin allows the mixing of two normally immiscible substances such as oil and water, thus helping to emulsify fat in the small intestine.

Lecithin belongs to the group of phospholipids and contains choline, which plays an important role in fat metabolism. It has a generally positive influence on the metabolism and promotes cell structure. It also stimulates the formation of immunological defence cells and supports the liver and blood circulation. In the mammary gland tissue, lecithins are responsible for the transfer of fats and proteins into breast milk. Lecithins support enzyme activity and increase performance and vitality. In addition, fertility is positively influenced.

In practice, various manufacturers offer specially designed fat powders for ration design that are already provided with lecithin. To support the sows’ metabolism, the animals can additionally be given B vitamins, endotoxin binders or electrolytes.

This is how much feed lactating sows need

Amount of feed required to cover the assumed energy requirement of lactating sows of 101 MJ ME at different energy densities (Source: Ralph Schemmer)

Good for sow and piglet

A sow with 14 to 15 piglets in her third litter has a daily energy requirement (maintenance plus performance requirement) of about 101 MJ ME. With a lactation feed of 12.8 MJ ME, the sow would have to consume about 7.9 kg of feed per day. If the energy content of the ration is adjusted by adding 3 percent fat and thus an energy content of about 13.5 MJ ME/kg is achieved, the sow would only have to eat about 7.5 kg of feed per day to cover the requirement.

In this way, it is possible for self-mixers to adjust the energy content of rations in the short term by adding 3 percent fat powder and to counteract the reduced feed intake in summer.

Increased fat content in the complete feed enables the lactating sow to absorb more highly digestible energy with the feed and thus has to melt down less body fat. This also relieves the liver, which is crucially involved in fat mobilisation. Ultimately, this has a positive influence on the fertility of the sows and their length of life.

With higher energy levels in the ration, milk yield also increases. As a result, the piglets consume more milk and thus more energy. Their growth is significantly improved. This is accompanied by lower piglet losses, a stable health status and increased weaning weights.

Adapt feeding strategy

Reduced protein and crude fibre combined with increased fat content will seriously decrease the heat production during digestion of the feed. Therefore, the protein content should be adjusted. High-protein rations lead to increased heat release immediately after feed intake, because the breakdown of protein into its amino acids causes heat. A protein reduced feed by using higher digestible protein sources and amino acids will give the sow enough amnio acids on small intestine level and reduce heat production. Next to this it is of course good for the environment (less ammonia emissions). The crude fibre content should also be kept in mind during hot periods. The fibre is utilised in the posterior digestive tract by microorganisms and during fermentation not only valuable volatile fatty acids are produced but also considerable amounts of heat.

Since a reduced feed intake can occur under heat stress despite an adjusted content of crude protein and crude fibre in the ration, the nutrient concentration, i.e. the amount per unit of weight, should also be checked and adjusted. The aim is to cover the nutrient requirement even with less feed.

Do not forget the water

Besides feeding adapted to the higher temperatures, the water supply of the animals plays an important role. On average, lactating sows need more than 40 litres of water per day, which can quickly rise to more than 50 litres. In summer, more water is also needed for thermoregulation.

For a high feed intake, not only the sufficient amount of water is crucial, but also the water temperature. Experiments have shown that when cool water (10 or 15 °C) compared to 22 °C warm water, water intake (plus 22 percent), feed intake (plus 40 percent) and milk yield of the sows (plus 20 percent) can be increased.

In addition, the flow rates or the water pressure of the drinkers and the water quality should be checked regularly. The quality has a significant influence on the palatability and thus the uptake of the water. To control water consumption, water meters can be installed per pen unit or compartment.

Our solutions for sows and piglets:


  • High-energy component, with lecithin supplement
  • Guarantees highest digestibility
  • Also available on a rapeseed basis


  • Combination product, from high-quality sweet whey, refined vegetable fats and lecithin
  • With a high proportion of medium-chain fatty acids