Photo: Lukiyanova Natalia/frenta/Shutterstock
Antioxidants are naturally occuring substances that can protect an animal organism from harmful influences. They prevent oxidation reactions termed as oxidative stress. Antioxidants, being a defense system in vivo, comprise several defense lines. The main defense line inhibits the formation of free radicals and reactive oxygen species by isolating metal ions while destroying superoxide and singlet oxygen, reducing hydrogen peroxide and hydro peroxides in every cell of the organism.
Performance losses and decline in livestock production as a result of the damage by free radicals and oxidative stress have become major issues and the subject of much research and concern in recent years. Free radical damage and oxidative stress are not diseases but are often the by-products of normal cellular processes.
Counteracting free radicals
Much attention has been paid in recent years to the involvement of free radicals and active oxygen in aging and in disease processes such as like inflammation, arthritis, heart disease, impairment of the immune system and cancer. Oxidative stress is an imbalance between increased levels of reactive oxygen species (ROS) and reduced antioxidant activity. Increased oxidative stress can potentially destroy tissues and induce damage to cellular structures.
Natural antioxidants are widely accepted worldwide and preferred to synthetic antioxidants. Aeschbach et al. (1994) reported that thymol, carvacrol and 6-gingerol possess useful antioxidant properties and may become very important in the search for “natural” replacements of “synthetic” antioxidant food additives.
The antioxidative properties of certain phytogenic substances have been attributed to the phenolic terpenes in their essential oils. Plants high in terpenes include oregano, rosemary and thyme. The essential oils from plants e.g. of the Labiatae family have been used at large as antioxidants in human and pet foods with high fat content.
Evaluating the influence of feeding Artemisia annua on muscle lipid oxidation products in broiler chickens, Cherian et al. (2013) recommended A. annua as a naturalphytogenic feed additive (PFAs) with antioxidant potential for use in poultry diets. Luna et al. (2013) reported the usefulness of natural phenols (main components of essential oils) as contained in thymol and carvacrol to delay lipid oxidation, which is the main cause of nutritional and organoleptic deterioration of birds’ meat.
Restricting antioxidative processes is of prime importance for proper animal health, growth, production and economic feasibility. Based on the available literature to date, PFAs comprising single or combinations of components offer a significant potential as a new generation of feed additives with pronounced antioxidative capacity for progressive and healthy food animal production.
Oxidation and Antioxidation
To explain antioxidation simply, an antioxidant binds potentially dangerous free radicals (FR) and pulls them out of circulation. A radical bound in this way cannot cause any more damage to the organism. When more ROS are formed than the antioxidants are able to intercept, the outcome is oxidative stress, the cause of many chronic diseases.
There are a variety of mechanisms for antioxidation, namely endogenous and exogenous (nutritional). However, all of them have the same positive effects counteracting harmful substances. As long as there are enough antioxidants available, free radicals pose no serious problem to the organism. But if too many free radicals are formed and not removed, all the biological structures suffer lasting damage. Therefore, it is absolutely useful and often necessary to support the animal through a variety of positive measures that are effective, valuable and at the same time, natural. Figure 1 represents the interplay between antioxidants and pro-oxidants.
Figure 1. The interplay: Antioxidation versus oxidation.
Antioxidative effects of phytogenics
In addition to the pronounced anti-inflammatory properties of phytogenic compounds in the digestive tract, protective effects of phytogenic compounds may also result from their antioxidative properties. Antioxidative effects were reported for a large number of plant substances.
An important cellular element is the transcription factor Nrf2. Activation of the Nrf2 pathway leads to the activation of genes responsible for cellular defense against ROS and detoxification of xenobiotics (chemical substances foreign to an organism). The PFA Digestarom® was found to upregulate Nrf2 target genes, i.e. cytochrome P450 isoform 1A1 (CYP1A1), heme oxygenase- 1 (HO-1) and UDP glucuronosyltransferase isoform 1A1 (UGT1A1), thus providing further evidence of the protective effects of phytogenic compounds at the cellular level (Figure 2).
Figure 2. Antioxidative effect of Digestarom® (up-regulation of Nrf2 target genes).
Therefore, the regular supplementation with PFAs through the diet may act as prophylactics against inflammatory reactions in the gastrointestinal tract by inhibiting the NF-KB pathway and stimulating the antioxidative transcription factor Nrf2.
Antioxidants and meat quality
Dietary antioxidants are recognized not only for their beneficial effects in the animal’s digestive tract, but also for their positive influence on meat quality.
Oxidation of lipids during food processing and storage is crucial because polyunsaturated lipids oxidize and form hydroperoxides which are vulnerable to further oxidation and/ or decomposition to secondary reaction products such as shortchain aldehydes, ketones and other oxygenated compounds. These may adversely affect the overall quality of food including taste, flavor, nutritional value, concentrations of toxic compounds and shelf-life.
The effects of dietary essential oil (Zataria multiflora) supplementation on the microbial growth and lipid peroxidation of broiler breast fillets during refrigerated storage were studied by Javan et al. (2012). They concluded that essential oil delayed the peroxidation and microbial spoilage of chicken breast fillets. Similar results were reported for chicken meat, turkey meat and fish using different phytogenic compounds.
In an experimental trial with broilers at the University of Athens, Greece, Mountzouris et al. (manuscript in preparation) observed that including the PFA Digestarom® P.E.P. in corn-soybean meal basal diets resulted in significantly (p<0.05) higher plasma and total antioxidant capacity of the meat as determined by the oxygen radical absorbing capacity (ORAC) method.
The antioxidative efficacy of Digestarom® additives has been shown under in vitro and in vivo conditions. These PFAs are effective in improving the antioxidant status of animals, as confirmed by an elevated antioxidative status in blood plasma, meat and the intestinal tract.
Enabling healthy meat production with enhanced storage quality is an added bonus to improved animal performance.
The effects of Digestarom® in intestinal cells
- Down-regulates inflammatory processes (NF-kB)
- Up-regulates antioxidant gut protection (Nrf2)
Source: Gessner et al., 2013