The problem

Both an issue of welfare and production efficiency, heat stress represents a global challenge in pig production. Correlated with the climate change predictions, we can only assume that the effects of heat stress will increase in severity in the coming years. Until recently, the only way to mitigate heat stress was by modifying the environmental factors on farm, but additional strategies, like nutritional cutting-edge techniques, are necessary to respond to the losses generated by the summer temperatures and the growing demand for high quality meat.

When pigs are exposed to temperatures outside their thermoneutral zone, the efficiency of production is compromised because nutrient utilisation is reprioritised to respond to the heat stress. Moreover, pigs are highly susceptible to heat stress due to an inability to sweat.

The impact

All of these factors place pigs at greater risk of health and production problems that can add up to millions of Euro annually in revenue losses to swine producers. Even more, phenotypes resulted from intense genetic selection are associated with increased metabolic heat production, thus more heat stress intolerance (Renaudeau et al., 2012a; Baumgard and Rhoads,2013). Revenue losses due to heat stress in pig industry happen all over the world – this is a global issue and not limited only to hot regions. For example, in the US, the swine industry alone loses €0.8 billion every year (Pollmann, 2010; Key and Sneeringer, 2014). These losses come from associated mortality due to heat stress; inconsistent growth, low feed efficiency, poor carcass quality and decreased usage of the facilities.

Heat stress not only affects young piglets, but it’s a threat for pigs of all ages.

For the animals (fatteners, and specially gilts), which are transported during warmer periods, a reduced water intake can be dramatic. It results in significant loss of body weight of around 5 to 10%. A more severe dehydration can ultimately lead to death.

In sows, heat stress can negatively impact the farrowing rates, the numbers of pigs born alive, but also the health and growth of piglets if the sow doesn’t produce enough milk. Indeed, hot weather leads to reduced appetite, which will negatively impact oestrus, ovulation rates and conception. The higher temperatures can also lead to the loss of some pregnancies. Modern hyperprolific sows have much longer farrowing periods, which can last six to seven hours. Those sows have a higher risk of becoming exhausted, and this is particularly true during warmer periods.

Evidence suggests that maternal exposure to heat stress has both immediate and long-lasting effects on piglet performance after birth. (Baumgard and Rhoads, 2013; Ross et al.,2015). Heat is known to reduce feed intake and milk production in sows (Rauw et al., 2020; Dourmad et al., 2015). This results in a drastic reduction in the growth of their litters pre-weaning. Therefore, in such conditions, it is not only imperative to support the sow, but it is also crucial to provide piglets with adequate hydration and to encourage them to consume solid feed, especially after the first week of life, when the nutritional needs of the litter surpass the available milk supply (Dourmad et al., 2015, Pluske et al., 2003).

The solutions

Without a doubt, the fastest method to address heat stress is to alter the farm microenvironment. But this comes with high costs, with most farmers not willing to make the extra investment. Genetic selection is a long-term possibility, however this comes along with reduced productivity.

Dietary approaches such as increasing fat and reducing the amount of crude protein or crude fibre and the use of complementary feed and supplementation are easily adaptable strategies that could bring benefits to pig production systems facing high temperatures. However, generally, these dietary recommendations could be inconsistent and may need local validation.

Other dietary strategies involve supplementing the gut with bio-active compounds (Rhoads et al., 2013). Many of the negative consequences that heat stress has on animal health and productivity are mediated by enhancing the intestinal barrier or at least ensuring its proper functionality. Thus, dietary strategies to prevent or minimise intestinal hyper-permeability are of particular interest and include antioxidants, specific amino-acids and minerals (Baumgard et al., 2012; Baumgard and Rhoads, 2013).

The Tonisity option

Tonisity International is dedicated to the innovative development of cutting-edge nutritional products. We care about bringing improved animal welfare, production outcomes and positive returns for farmers. Both our products, Tonisity Px and Tonisity PxWare pioneered through disruptive technology and deliver key ingredients that nourish the small intestine and make pigs more resilient to stress.

A rapid way of minimising the impact of heat stress on piglets pre-weaning and to maintain litter growth is to supply Tonisity Px 3% solution from day 2 to 8 and as poured on dry feed at weaning.

Study data has shown that the 2-8 day protocol provides optimal hydration while boosting gut health, thus reducing pre-weaning mortality by an average 20% (data on 70 studies in 22 countries, totaling 148,000 pigs). On the other hand, mixing Tonisity Px with creep feed will encourage the piglets to consume creep feed and maintain their growth, thus reducing the dependency on sow milk and preparing them for weaning transition.

The evidence

All of these were clearly seen in a 6,000-piglet study conducted in the summer of 2020 in Spain, during a heatwave.

• The benefits of administering Tonisity Px were obvious, with pre-weaning mortality being reduced by 54%, from 10.3% to 4.8% (P<0.0001). This translated in an extra 0.71 piglets/litter
• Furthermore, the percentage of fall-behinds (piglets that looked sick or weighed <4.5kg at weaning) was 62% lower in the TPX group than in the Control group (10.5% vs. 27.3%; P<0.0001). This lower frequency of fall-behinds is likely due to TPX piglets showing higher vitality and better suckling abilities, especially since in high environmental temperature, such as Spain in mid-summer
• Post-weaning, administering the same bioactives but through the waterlines, in the form of Tonisity PxW has been shown to improve water intake by 1.4-1.8x in the same Spanish study
• In other studies, Tonisity Px, has been shown to stimulate beneficial bacteria and decrease potentially pathogenic bacteria, both pre and post-weaning. A healthy microbial community in the gut is critical to minimise the negative performance consequences associated with heat stress
• Furthermore, a meta-analysis of seven USA studies (31,861 piglets), which involved the transport of piglets for three to fifteen hours showed a highly-significant (P<0.01) 1.7x higher water intake when the Tonisity PxW was in the water. As a result, the post-weaning mortality and the number of fall-behinds were also significantly reduced (P<0.0001)

To conclude. Tonisity’s product range provides a rapid and reliable strategy to minimise the effects of heat stress and support pig growth and health pre- and post-weaning, leading to a strong return on investment for the producer.

Effective thermoneutral zones

The thermoneutral zone is a range between lower critical temperature and the point where metabolic rate is actively reduced to heat stress.

In this zone pigs don’t need to spend energy to maintains their body temperature, so their production rate is most efficient. For lower temperatures, the animals must metabolise body fat or increase feed intake to maintain their body temperature. Above the thermoneutral zone they will reduce their activity, increase breathing rate and reduce feed intake. The table to the right (adapted from the Pork Industry Handbook) shows the thermal comfort ranges for pigs at various stages of production.

It’s important to understand that the thermoneutral zone is affected by various factors such as feed intake, stock density, floor type, air moisture and ventilation.