Heat stress is a growing concern in swine production, because it can have negative consequences on feeding behaviour, growth performance, and animal welfare. Lallemand Animal Nutrition has always advocated for nutritional strategies to include the feeding of the live yeast Saccharomyces cerevisiae boulardii CNCM I-1079 (available in its LEVUCELL SB solution) to help alleviate the effects of heat stress in pigs. And now, thanks to a 4-year study supported by the company, it can shed new light on the exact modes of action involved in this process.
The research study, conducted by doctoral student Aira Serviento, in partnership with Etienne Labussière and David Renaudeau from France’s National Research Institute for Agriculture, Food and Environment (INRAE), found that feeding LEVUCELL SB to male finishing pigs subjected to heat stress improved their resistance to the condition due to improved insulin sensitivity.
In this Industry Perspectives, Lallemand Animal Nutrition’s Technical Manager for Yeast Derivatives & Swine Solutions, Bruno Bertaud, and its Global Swine Applications Manager, David Saornil, unpack these findings for Feedinfo in more detail, sharing the valuable insights gathered from the research into how live yeast supplementation can improve pigs' resilience to heat stress and enhance their overall health and productivity.
[Feedinfo] Mr Bertaud, remind us, at what temperatures do pigs start showing signs of heat stress? How does it affect gut integrity, and what are the potential consequences of this?
[Bruno Bertaud] Heat stress is not only a matter of temperature, but relative humidity should also be considered as well as it adds to the stress. Sows can suffer from heat stress even at temperatures lower than 25°C, while fattening pigs can undergo heat stress when the ambient temperature goes above 25°C.
During heat stress, there is a redirection of blood flow to the skin’s surface to maximise the heat exchange. A consequence of this is a vasoconstriction at the gastrointestinal tract level to redirect the blood flow towards peripheral circulation, which affects gut wall integrity. This has several impacts, both on performance and health. First, the absorption of nutrients is reduced, which further contributes to decreased growth performance. Second, the gut epithelium becomes permeable to pathogens and endotoxins which can then translocate into the blood stream. This, in turn, leads to an inflammatory response, pro-inflammatory cytokine production, and – in more severe situations – a leaky gut and diarrhoea. Finally, the inflammatory response also causes a reduction in the feed energy dedicated to growth, further contributing to loss of performance.
[Feedinfo] Are there any long-term health effects on pigs that experience repeated episodes of heat stress? What about sows and their progeny?
[Bruno Bertaud] Heat stress compromises a variety of production parameters including growth, carcass composition, and reproduction. Summer heat waves can have long-lasting effects on performance and physiological responses. Evidence suggests that maternal exposure to heat stress has long-lasting effects on postnatal offspring performance.
[Feedinfo] How big an impact can nutritional strategies really make in reducing the impact of heat stress? Wouldn’t interventions like environment management be sufficient?
[Bruno Bertaud] Of course, management of the environment and especially the farm building (isolation, air temperature, cooling systems, etc.) is a must to prevent heat stress and should be considered first. Nutritional strategies should be considered within a global management strategy, as well as animal genetics for the longer term (choice of genetics with lower sensitivities to heat stress).
[David Saornil] That being said, feed plays a non-negligeable role in the regulation of heat produced at the metabolic level. What we call it the “Thermic Effect of Feeding” (TEF) and it is a measure of how much the feed increases energy expenditure – expressed as heat – due to the energy required to digest, absorb, and metabolise the nutrients. Playing with the 3 main categories of macronutrients in a pig’s diet (carbohydrates, proteins and fat) can impact the TEF. For instance, reducing the level of protein in the diet leads to a drop in the post-prandial thermogenic response. This is due to a reduction in the protein digestion metabolism, which, in turn, reduces the negative impact of heat stress. Increased levels of dietary fibre generate heat due to fibre fermentation in the large intestine, while fat digestion and assimilation generates less heat production compared to protein and fibre. Thus, formulating diets with an increased level of dietary fat and reduced levels of protein and fibre can contribute to a lower TEF. In addition, other nutritional strategies might be considered, like the use of dietary antioxidants, chromium and/or betaine, as well as all strategies that can improve gut integrity, including probiotic yeasts.
[Feedinfo] Looking at LEVUCELL SB, can you briefly remind us of how live yeast supplementation can impact pigs' resilience to heat stress?
[Bruno Bertaud] Considering the live yeast Saccharomyces cerevisiae boulardii CNCM I-1079, which is the most largely documented probiotic strain in monogastric animals, more than 50 scientific publications have supported its beneficial effects on gut health.
Under heat stress conditions, S. cerevisiae boulardii helps maintain optimal gut barrier integrity functions and reduces the risk of pathogen endotoxin translocation into the blood stream with associated inflammation.
Moreover, all the benefits of live yeast feeding on lactating sows and fattening pigs’ performance – that have been otherwise largely demonstrated – also apply under heat stress, at a time when reduced feed intake can take a toll on production performance. Indeed, numerous trials conducted around the world show consistent positive effect on sows’ feed intake, number of piglets born alive, sow condition, number of weaned piglets, and more.
[Feedinfo] Now, a 4-year study supported by Lallemand that looked at this process a little closer, specifically at the modes of action involved in how live yeasts go about supporting heat-challenged pigs, was recently completed. What exactly did this study entail and what were the main findings that you can share with us?
[David Saornil] Yes, we supported a 4-year research programme in partnership with INRAe (PEGASE, Rennes) dedicated to the mechanisms underlying the effects of live yeasts on energy metabolism and heat tolerance in pigs. Within this programme, a specific trial was conducted using metabolic chambers to evaluate the effect of our live yeast supplementation (LEVUCELL SB) and feeding frequency in male finishing pigs subjected to heat stress.
The study showed increased resilience to heat stress in the supplemented pigs vs. control pigs, something that was already shown in past studies. But this time we went further into the metabolism modes of action. What is new here is that this increased resistance to heat stress could be attributable to improved insulin sensitivity of the pigs fed the live yeast! It was also demonstrated that pigs supplemented with the live yeast were more efficient dissipating heat through the latent route, which means water evaporation in the lungs, and therefore had a faster thermal adaptation after meals.
The study also evaluated the benefit of the live yeast on pigs’ feeding behaviour, metabolism and growth performance.
Indeed, under heat stress, pigs tended to eat less and divert their energy metabolism away from growth.
In pigs supplemented with live yeast, the impact of heat stress on feeding behaviour was alleviated, with shorter inter-meal intervals. It was previously shown by Labussière et al., in 2022, under similar conditions, that supplemented animals increased their meal frequency and, thus, their total feed intake.
Better adaptation to heat stress conditions in live yeast supplemented pigs resulted in better energy retention, which also confirmed previous findings.
Altogether, it was shown that improved heat tolerance of live yeast supplemented pigs lies in their ability to maintain the dynamic equilibrium between heat production and loss throughout the day, though several mechanisms.
[Feedinfo] Let’s zoom in on insulin sensitivity. How exactly do live yeasts contribute here and how can improved insulin sensitivity help mitigate the effects of heat stress?
[Bruno Bertaud] Insulin is a key hormone in many metabolic processes, especially related to energy metabolism. In general, blood glucose (along with other nutrients) rises after a meal and insulin is released by the pancreas to promote glucose uptake.
Heat exposure has been reported to decrease insulin sensitivity, with, as a direct consequence, an increased basal and circulating insulin concentration.
As insulin inhibits triglycerides hydrolysis in adipose cells into glycerol and free fatty acids, the direct effect of heat stress on fat deposition might be connected to the reported altered insulin response during this time.
Many studies have already either demonstrated or hypothesised that an improved insulin sensitivity is important in coping with heat stress. Lower insulin levels in the blood (to maintain glucose homeostasis) can thus help reduce or maintain a lower body temperature.
The live yeast study we mentioned shows that for the supplemented pigs, the insulin/glucose ratio was significantly lower around meals than that for the control pigs, which may contribute to higher energy efficiency during heat stress. This improved sensitivity to insulin can be explained by two main mechanisms of action of the live yeast: 1) improved intestinal integrity during stress and 2) increased production of short chain fatty acids in the gut, thanks to microbiota modulation. It is noteworthy that in humans, S. boulardii supplementation has been reported to attenuate diabetic related complications such as hyperglycaemia (due to impaired insulin activity or production) by microbiota modulation and improved immune responses.
[Feedinfo] The trial also noted increased water intake, especially around meals, for the live yeast supplemented pigs. What is behind this? Why would yeast supplementation impact water intake?
[Bruno Bertaud] Indeed, the live yeast treated pigs showed increased water intake, especially around meals. This is very important because pig’s main strategy to dissipate heat is water evaporation through panting, so under increased heat it is easy to imagine that their water requirements are higher. With live yeast, the increased water intake will increase the pigs’ ability to dissipate heat through panting and this could be measured: the pigs’ body temperature went down quicker after a meal as compared to the control, indicating an improved thermoregulation response and heat dissipation with the live yeast. For now, we are not totally sure of the why. But a lot more remains to be explored and we, as always, remain dedicated to learning what we can and employing those findings to improve animal health, wellbeing and productivity!
Published in association with Lallemand Animal Nutrition