Carefully selected polyphenols can meet an animal’s antioxidant demands, which are currently provided by vitamin E as well as additional polyphenols that further support the antioxidant capacity beyond the lipid environment. This strategic swap offers a multifaceted strategy that supports protection against free radicals and helps safeguard animal health and performance.
Technical Commercial Manager – Phytogenics
Selko
Like many commodities, vitamin prices are volatile and tend to surge when a disruption occurs in the supply chain. The recent spike surge in vitamin E prices has led nutritionists and producers to seek alternative sources of this powerful antioxidant well known for its anti-ageing and beneficial health properties; particularly as vitamin E activity is limited to the body’s lipid milieu.
In this context, natural polyphenols emerge as a promising solution for tackling oxidative stress in ruminants as well as monogastric species. When synergistically combined, polyphenols can serve as a partial substitute for vitamin E in animal feed, while enhancing antioxidant defences beyond the capabilities of vitamin E alone.
FREE RADICALS: THE CAUSE OF OXIDATIVE STRESS
Metabolic processes naturally produce free radicals, the primary culprits behind oxidative stress. These reactive molecules, including superoxide, hydrogen peroxide, and hydroxyl radicals, are generated during energy (ATP) production. The rate of an animal’s growth and its health status directly influence the production of free radicals. It’s crucial to understand that rapid growth, associated with increased metabolic activity, leads to a surge in oxidative stress. Similarly, health challenges trigger the immune system to produce more free radicals, exacerbating oxidative stress and negatively affecting animal health. Understanding the impact of growth and health challenges on free radical production is enlightening and can guide effective strategies for managing oxidative stress.
CONSIDERING THE CONSEQUENCES OF OXIDATIVE STRESS
To understand why it is so important to reduce free radicals in livestock production, it is helpful to consider the harm that free radicals pose to animals and ultimately to producers’ businesses. The negative consequences of free radicals can wreak havoc on cell membranes, proteins, and DNA, leading to tissue damage and significant health implications for animals. Supplementing animals’ diets provides an interesting opportunity to protect the animal from oxidative stress.
MANAGING OXIDATIVE STRESS WITH ENZYMES, ANTIOXIDANTS, AND DAMAGE REPAIR
Understanding the two key strategies for combatting free radicals and reducing oxidative stress can empower producers’ efforts to manage animal health. The first line of defence involves enzymes that convert free radicals into harmless substances like water and oxygen. Enzymes such as catalase, superoxide dismutase, and glutathione peroxidase, containing selenium, play a crucial role in this strategy. The second line of defence is formed by antioxidants, including vitamins E and C, lipoic acid, and glutathione, which neutralize free radicals, preventing them from causing further damage.
Antioxidants reduce free radicals by donating a hydrogen atom. Vitamin E, for example, contains a benzene ring with a hydroxyl group attached. The electrons in the benzene ring are mobile, allowing the hydrogen in the hydroxyl group to separate and neutralise a free radical. Vitamin E also has a long lipophilic tail, allowing it to function as a lipid in digestion and the body (Figure 1).
COMBATTING FREE-RADICAL DAMAGE – ALTERNATIVES TO VITAMIN E
Vitamin E’s function as a gene regulator is more critical than its antioxidant properties. Nothing can replace vitamin E in this capacity. However, other antioxidants can replace vitamin E to prevent and combat free-radical damage if they function in the same cellular region and have a similar affinity for free radicals (Figure 2).
In fact, other antioxidants may be even more effective than vitamin E in the fight against free radicals. A vitamin’s bioavailability should always be considered given that the animal must be able to access and utilize the vitamin to obtain its beneficial properties. The synthetic vitamin E used in animal nutrition is a blend of eight stereoisomers, one of which only one has the same spatial structure as naturally occurring vitamin E which offers good bioavailability. The liver does not adequately recognise the remaining seven stereoisomers, which are primarily returned to the digestive tract and excreted unused.
CONSIDERING BIOAVAILABILITY AND SPECIES
The bioavailability of vitamin E in cattle is highly variable and depends on the balance between intake, absorption, retention, and degradation of vitamin E. The bioavailability of vitamin E in pigs and poultry is affected by several factors, such as the age and physiological status of the animals, the dietary fat content and composition, and the presence of other antioxidants and pro-oxidants. Furthermore, vitamin E’s half-life shortens with increasing doses, making it hard to achieve plasma levels greater than three times the baseline. To ensure a high level of antioxidant defence in animals, particularly those who are fast-growing or have health issues, it is critical to combine a variety of antioxidants that function synergistically and complement one another.
POLYPHENOLS IN SELKO AOMIX ARE POTENT ALTERNATIVES TO VITAMIN E
Polyphenols are a class of plant chemicals with antioxidant properties. These molecules’ basic structure includes a phenol group, which is related to vitamin E. Polyphenols’ antioxidant potential has long been recognised, and over a century ago, they were close to being classified as vitamins due to the antioxidant protection they provide.
Some polyphenols have more hydroxy groups bonded to benzene rings per unit weight than vitamin E, giving them even more antioxidant activity (Figure 3).
However, not all polyphenols can be used as a direct replacement for vitamin E’s antioxidant effect. Bioavailability, radical affinity, tissue dispersion, and metabolism must all be considered.
In ruminants, bioavailability is directly proportional to three factors: polyphenol susceptibility to fermentation in the rumen; the type of fermentation products produced; and the bioavailability of bypass polyphenols or polyphenol fermentation products. Citrus, for example, contains naringenin, which can skip rumen fermentation and has a high bioavailability in the small intestine. Conversely, proanthocyanidins are too big to digest in the small intestine and must be fermented to produce absorbable antioxidants. Bio-efficacy is affected by both the substrate and the fermentation conditions.
Polyphenols for monogastric species must be chosen according to their digestibility and intestine absorption. According to studies, quercetin, rosemarinic acid and resveratrol are highly bioavailable.
In contrast, grape-based proanthocyanidins produce almost no useful antioxidants in monogastric species. Together with the low bioavailability of grape polyphenols and proanthocyanidins in poultry, these antioxidants are better suited as an alternative to vitamin C as they are water soluble antioxidants. Therefore, Grape polyphenols should rather be viewed as complementary to vitamin E and not as a replacement for vitamin E. This is because only fat-soluble antioxidants can prevent lipid oxidation.
Taking the digestive physiology of monogastric animals and ruminants into account, Trouw Nutrition developed species-specific synergistic blends of polyphenols that contain a high ratio of fat-soluble antioxidants for its Selko AOmix portfolio. Plant raw materials were chosen for ruminants because they contain rumen-bypass polyphenols which either retain their antioxidant properties after having passed through the rumen or polyphenols, which are fermented in the rumen into powerful, post-rumen available antioxidants. For monogastric species, on the other hand, plants were selected rich in polyphenols that are readily absorbed and exert their antioxidant properties without the need to be hydrolysed by (bacterial) fermentation. The produced compounds can replace and/or supplement the antioxidant protection that most animals currently obtain from vitamin E, avoiding the declining returns of larger dosages of vitamin E while simultaneously complementing the antioxidant protection from vitamin E in a cost-effective way.
Figure 4. Selko AOmix in combination with vitamin E reduces MDA-levels (marker for oxidative stress) in piglets under heat stress conditions. Nutreco R&D in cooperation with the University of Gent, 2012.
The efficacy of Selko AOmix has been confirmed through various in vivo studies. For example, a study in which lambs were fed a diet high in unprotected linseed oil found that polyphenol blends delayed and reduced fat peroxidation. In trials with hens and pigs, animals fed polyphenol blends that suffered heat stress showed no increase in oxidative stress, which is consistent with a high dose of vitamin E. Field experience has shown that Selko AOmix can safely and effectively replace a portion of the vitamin E need (Figure 4).
In conclusion, carefully selected polyphenols that consider differences in digestive physiology, radical affinity, and tissue distribution, can meet an animal’s antioxidant demands, which are currently provided by vitamin E as well as additional polyphenols that further support the antioxidant capacity beyond the lipid environment. This strategic swap offers a multifaceted strategy that supports protection against free radicals and helps safeguard animal health and performance.
About Marlien de Kock
Marlien de Kock is the Global Technical Commercial Manager for Phytogenics for the Europe, Middle East, and Africa Region at Selko, the feed additive brand of Trouw Nutrition. She holds a BSc (Agric) Hons. degree from the University of Pretoria and an MSc (Agric) from the University of Stellenbosch. During the first 25 years of her career, she worked in the animal pharmaceutical industry at various global companies.
Marlien de Kock has extensive experience in residue control and reduction of carryover of pharmaceuticals, especially antibiotics, in food for human consumption. In September 2021, she joined Trouw Nutrition South Africa as a Product Manager: Feed Additives, and in April 2023, she moved to Selko to take on her current role.
