Animals face every day various kind of stress: change of diet or raw material quality, hot temperature, diseases, handling and manipulations … Stress triggers the production of free reactive radicals in cells which oxidize lipids or proteins. These free radicals are normally regulated but under stress conditions, free radicals' level can increase dramatically and results in significant damage to cell structures and, to some extent, affect the performance and/or health of animal.

A strategic approach of natural antioxidants

In order to avoid negative effects from oxidative stress, cells contain naturally present antioxidant mechanisms. In an ideal situation, a balance between oxidation and antioxidant mechanisms is established safeguarding cell integrity and function. Antioxidant mechanisms are mitigating cell oxidative stress by neutralizing reactive radicals. In highly productive animals or during stressful periods, additional components with antioxidant capacity are often provided on top of the naturally present antioxidant mechanisms in the body to support health of animals. Many ingredients have shown interesting antioxidant effects. More precisely, several groups of molecules have shown an effect to help balance oxidation and antioxidant mechanisms in the organism. Among these groups, different types of natural ingredients containing polyphenols have shown antioxidant effects. Polyphenols are natural compounds present in plants with numerous biological activities. Several studies have explored the properties of polyphenols in anti-inflammation and oxidation, the mechanisms involved in signaling pathways activated upon oxidative stress, as well as the possible roles of polyphenols in specific disorders. Polyphenols are present in herbs, spices, stems, flowers, … and even seaweeds. They are the secondary metabolites of plants involved in defensive system.

It is difficult to determine the best source of natural antioxidants: Environmental factors, such as the type of the soil, exposure of the light, rainfall, culture methods, and fruit yield per tree, have a strong impact on final concentration and activity. In vitro methods are a good preliminary approach to evaluate antioxidants, nevertheless, in vivo trials are necessary to validate solutions. The scientific approach to determine the ideal solution can therefore be split in 2 steps: the evaluation of individual ingredients and their variability ; and the formulation of optimal ingredients.

To illustrate the variability of ingredient, a recent work was achieved (See figure 1) to measure the antioxidant activity of phlorotannins from various seaweeds and various geographic origins. Phlorotannins are a type of polyphenols found in brown algae such as kelps, and that can only be found in seaweeds. In the present example, one can see that between seaweeds or even for the same species, variability can be very high. The same applies to other plants. This is why formulators needs to carefully select the source and the quality of antioxidant to guarantee a consistent quality and efficacy in feed.

Regarding formulation or the selection of solutions, considering the numbers of natural antioxidants, this can be a very time-consuming activity, not to say a total waste of time. More importantly, several studies have highlighted the potential synergies between different sources of polyphenols (Liu, 2004). When combining polyphenols from 4 different sources, the dose-response curve of antioxidant activity was shifted to the left and the median effective dose (EC50) of the combination was 5 times lower than the EC50 of each single source, suggesting synergistic effects when combining sources. As a matter of fact, combining various sources of polyphenols looks like the most strategic and most resilient approach.

Strengthening the antioxidant pool for more resilience

Countless studies have shown the potential of natural antioxidants to strengthen or complement the activity of other antioxidants, such as vitamin E, in feed. This effect is well documented, for many commercial solutions. The interest for such application is driven by technical and economic considerations and is of high interest in case of price crisis.

Recent trials made with an exclusive blend of natural antioxidants, including polyphenols from fruits, vegetables and seaweeds, showed how these solutions could be used to optimize formulations and maintain the performance of animals. There is now sufficient evidence globally to invest in such strategy, even though this depends of course of the level of supplementation and the formulation of feed, as well as the economic environment and potential savings.

Supporting performance during stress events

While farm animals are expected to perform at the top of their genetic potential, oxidative stress tend to occur during normal conditions as well. Supplementation of natural antioxidants supports the animal to overcome all kind of environmental stressors during its highly productive life.

Heat stress would be a good example of stress that can affect the performance and health of animals. Several studies highlighted the effect of heat on various parameters (Tawfeek, 2014). Such event had an impact on performance of animals but also on the final meat quality:

· For instance, in birds, it was observed that higher ambient temperature reduced severely body weight, feed intake, and feed efficiency as well as increased abdominal fat and mortality rate

· In parallel, heat stress significantly increased malondialdehyde and decreased protein and glutathione peroxidase, which can have a direct effect on meat quality and drip loss

Fortunately, supplementation of antioxidants can alleviate many of these effects, as several results indicate that the supplementation of diets with antioxidants, can contribute to overcome the deleterious effects of heat stress on broilers' performance.

As for swine, more recent research showed that natural antioxidants could be beneficial to pigs in reducing the effects of oxidative stress induced by heat stress (Jócsák, 2020) and therefore support better growth, better health and better meat quality.

Optimizing formulation and securing performance with a flexible and natural antioxidant solutions

As a conclusion, natural antioxidants, when they are based on a rigorous process of selection and formulation, can be considered as a flexible tool for nutritionists, to optimize feed formulations over the time, and represent as well a good tool to mitigate negative effects of various stress and challenges. At the end of the day, using only one raw material with some antioxidant properties might be very risky due to the variability of composition and activity. Nevertheless, new generation of natural antioxidants, combining high quality and consistent sources of phytogenics and phycogenics (ie metabolites from plants and seaweeds) offer now new perspectives to nutritionnists, to support performance of animals, secure meat quality and reduce health challenges during stress events, with flexible and cost effective solutions.

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Article made possible through the contribution of Dr. Stephanie Ladirat and NUQO

Resilient approach to reduce damages from stress and support performance