Figure 2 - Heat Stress consequences at the gut level according to the application of strategies that stabilise the physiological status of the animal.
Gut of animals without strategies* Leaky gut
Inappetence Poor Nutrient Uptake
Heat stress conditions
Gut of animals with strategies* Gut barrier
Appetite Nutrient uptake
Toxins
Pathogens Water
Nutrients
Immune Cells *Strategies based on modulation of feeding behaviour and stablization of the physiological condition of the animal
management (e.g. avoiding movements of animals in the midday) and nutrition (e.g. adding higher levels of vitamin E and Selenium). Therefore, strategies focused on keeping a good level of feed intake are crucial. In cattle and swine, the use of certain feed additives could have an effect on their eating behaviour thanks to their potential of inducing endocrine signalling (e.g. CCK, GLP-1), which help the animal to keep intake and modulate the feeding pattern (e.g. increasing the number of meals, reducing the meal size) independently of the environmental conditions (Figure 1). The implementation of these additives in advance is a useful strategy to prevent the immediate drop in feed intake and its direct consequences due to HS conditions, which should be maintained along the whole challenging period.
Alternative nutritional approaches Another approach may be to support nutritional strategies (e.g. protein reduction, increasing levels of fat,…) with feed additives that are focused to improve digestibility aspects of the diet or that endogenously are improving exocrine secretions and aspects of lipid metabolism. For example, it is well described that certain spices have the potential to
increase exocrine secretions (e.g. pancreatic lipase) and improve fat digestibility, resulting in better feed efficiency. On the other hand, to keep gut integrity is a must, apart from avoiding that the animal gets metabolically collapsed (e.g. respiratory alkalosis) when trying to cope with HS. In this aspect, attention would be paid on how to keep a low inflammatory status in the animal, locally (at the gut level) and systemically, to contribute to stabilise the physiological balance. Research of plant bioactives present in nature with antioxidant (e.g. polyphenols) and anti-inflammatory (e.g. triterpenes) properties have the potential of being used in animal nutrition as feed additives contributing to strategies that help the animal to become more resilient to HS consequences (Figure 2).
Implementing multiple HS strategies In summary, heat stress produces a wide range of negative consequences, some of them with long term effects. For this reason, it is crucial to approach this problem applying multiple strategies, but the key may be to implement them in advance before affecting the physiological status of the animal that has a long recovery.
▶ HEAT STRESS | MAY 2021 43
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