ANTIOXIDANTS AND ITS BENEFICIAL ROLE IN ANIMAL HEALTH
Nanotechnology, the manipulation of materials at the nanoscale, has permeated various fields, and its applications in veterinary medicine are transforming the landscape of animal healthcare. The unique properties of nanomaterials, such as their size and surface characteristics, enable innovative approaches to diagnosis, treatment, and prevention of diseases in animals. This article explores the diverse applications of nanotechnology in veterinary medicine, showcasing its potential to revolutionize animal health.
Antioxidants are a group of substances which even at low concentration significantly inhibit or delay oxidative processes. Oxidation is a chemical reaction that transfers electrons from a substance to an oxidizing agent. Antioxidants act as “free radical scavengers” and hence prevent and repair damage done by these free radicals. Health problems such as heart disease, macular degeneration, diabetes, cancer etc. are all contributed by oxidative damage. Antioxidants enhance immune defense and therefore lower the risk of cancer and other infections. Thus antioxidants can be used as ingredients in dietary supplements in the hope of maintaining health and boosting up immune status of animals. In recent years there has been an increased interest in the application of antioxidants to medical treatment as research is showing linking of diseases to oxidative stress. Residual level of antioxidants in animal by–products like milk, meat and egg is another emerging field of livestock nutrition as antioxidant enrichment of food products is currently receiving much public attention with respect to their potential to promote better health.
History
In past, the term “antioxidant” was used to refer specifically to a chemical that prevented the consumption of oxygen. Use of antioxidant begins with extensive study in important industrial processes, such as the prevention of metal corrosion, the vulcanization of rubber, and the polymerization of fuels in the fouling of internal combustion engines. Role of antioxidant in biological systems begins with their use in preventing the oxidation of unsaturated fats, which is the cause of rancidity (German, 1999). The possible mechanisms of action of antioxidants were first explored when it was recognized that a substance with anti-oxidative activity is likely to be one that is itself readily oxidized. Research into how vitamin E prevents the process of lipid peroxidation led to the identification of antioxidants as reducing agents that prevent oxidative reactions, often by scavenging reactive oxygen species before they can damage cells (Wolf, 2005).
Functional antioxidant system in the body
Body reacts to oxidative stress through complex mechanism of action interlinked to each other comprise of different enzymes, low molecular weight proteins, high molecular weight proteins as,
- Enzymes Their function in body is to prevent generation of reactive oxygen species, removal of potential antioxidants or transfer of reactive oxygen or nitrogen species into relatively stable compound, e.g. superoxide dismutase (SOD), catalase, and glutathione peroxidase 2. High Molecular Weight Proteins These high molecular weight proteins present in plasma, bind to redox active metals and limit the production of metalcatalyzed free radicals e.g. albumin, ceruloplasmin, transferrin and haptoglobin (Halliwell and Gutteridge,1990). Albumin and ceruloplasmin can bind copper ions, and transferrin binds free iron. Haptoglobin binds heme-containing proteins and can thus clear them from the circulation. 3. Low Molecular Weight Antioxidants These proteins are subdivided into lipid-soluble antioxidants (tocopherol, carotenoids, quinones, bilirubin and some polyphenols) and water-soluble antioxidants (ascorbic acid, uric acid and some polyphenols). They delay or inhibit cellular damage mainly through their free radical scavenging property.
Mechanisms of Antioxidant Functions
Antioxidants system in the body works via various mechanisms including:
1. Preventive antioxidants – suppress formation of free radicals e.g. catalase (Fe containing) and glutathione peroxidase (Se containing), two antioxidant enzymes, decompose hydrogen peroxide, preventing the formation of oxygen radicals.
2. Free radical scavengers – confer stability to the ‘reactive’ species by donating an electron and become oxidized themselves to form a more stable radical e.g. alpha-tocopherol (vitamin E) scavenges peroxyl radicals and is converted to a tocopherol radical. Illustrating antioxidant interactions, the vitamin E becomes “re-activated” by ascorbic acid donating an electron which in turn forms an ascorbate radical in the process.
3. Sequestration of metal by chelation – Although trace minerals are important dietary constituents, they can act as pro-oxidants (promote free radical formation). Since trace minerals such as Fe and Cu can propagate the formation of more reactive radicals they are kept bound to transport proteins such as transferrin or ceruloplasmin, rendering them less available to contribute to radical or prooxidant formation.
4. Quenching of active oxygen species – Antioxidants can convert active oxygen species to more stable forms; for example, carotenoids and vitamin E stabilize singlet oxygen radicals, forming less reactive hydrogen peroxide.
Animal Studies of Antioxidants:
Vitamin C protective effect may partly be mediated through its ability to reduce circulating glucocorticoids. The suppressive effect of corticoids on neutrophil function in cattle has been alleviated with vitamin C supplementation. Vitamin C and E supplementation resulted in a 78% decrease in the susceptibility of lipoproteins to mononuclear cell-mediated oxidation (Rifici and Khachadurian, 1993). Supplementation of vitamin E and Se have been shown to provide protection against infection by several types of pathogenic organisms, as well as improve antibody titers and phagocytosis of pathogens. For example, calves receiving 125 IU of vitamin E daily were able to maximize their immune responses compared to calves receiving low dietary vitamin E (Reddy et al., 1987). Supplemental vitamin E may enhance recovery from bovine respiratory disease. Antioxidants, including vitamin E, play a role in resistance to viral infection. Vitamin E and Se deficiency allows many viral diseases in animals by changing the viral phenotype, such that an avirulent strain of a virus becomes virulent and a virulent strain becomes more virulent (Beck, 1997). Supplementing vitamin E at higher than recommended levels (Dairy cattle NRC, 2001) has improved control of mastitis. Smith and Conrad (1987) reported that intramammary infection was reduced 42.2% in vitamin E-Se supplemented versus unsupplemented controls. The duration of all intramammary infections in lactation was reduced 40 to 50% in supplemented heifers. A known consequence of vitamin E and Se deficiency is impaired PMN activity. Further, postpartum vitamin E deficiencies are frequently observed in dairy cows. Dietary supplementation of cows with Se and vitamin E results in a more rapid PMN influx into milk which cause intramammary bacterial damage and increased intracellular kill of ingested bacteria. Subcutaneous injections of vitamin E approximately 10 and 5 d before calving successfully elevated PMN alphatocopherol concentrations during the periparturient period. Currently, it is suggested that peripartum dairy cows receive 2,000 to 4,000 IU vitamin E/d for optimal udder health (Seymour, 2001). Carotenoids have been shown to have biological actions independent of vitamin A. Recent animal studies indicate that certain antioxidant carotenoids which lack vitamin A activity, can enhance immune function, act directly as antimutagens and anticarcinogens, protect against radiation damage, and block the damaging effects of photosensitizers. Also, carotenoids can directly affect gene expression which may enable carotenoids to modulate the interaction between B cells and T cells, thus regulating humoral and cell-mediated immunity (Koutsos, 2003). Vitamin A and beta-carotene have important roles in protection against numerous infections including mastitis. Beta-carotene supplementation appears to stabilize PMN and lymphocyte function, both key components in defense against infection, during the period around dry off. Beta-carotene enhanced the bactericidal activity of blood and milk PMN against S. aureus but did not affect phagocytosis. Control of free radicals is important for bactericidal activity but not for phagocytosis. The antioxidant activity of vitamin A is negligible; it does not quench or remove free radicals. Beta-carotene, on the other hand, does have significant antioxidant properties and effectively quenches singlet oxygen free radicals (Mascio et al., 1991).
Understanding Oxidative Stress
- Free Radicals:
- Free radicals are highly reactive molecules with unpaired electrons, making them prone to react with and damage cellular structures, including proteins, lipids, and DNA.
- Oxidative Stress:
- Oxidative stress occurs when there is an imbalance between the production of free radicals and the body’s ability to neutralize them. This imbalance can lead to cellular damage and contribute to various health issues.
Sources of Antioxidants
- Endogenous Antioxidants:
- Animals produce their own antioxidants, including enzymes like superoxide dismutase (SOD), catalase, and glutathione peroxidase, which work within cells to neutralize free radicals.
- Dietary Antioxidants:
- Certain vitamins (C and E), minerals (selenium and zinc), and phytochemicals (flavonoids and carotenoids) serve as antioxidants in the diet. Animals obtain these through forage, grains, fruits, and vegetables.
Mechanisms of Action
- Free Radical Scavenging:
- Antioxidants neutralize free radicals by donating electrons, preventing them from causing cellular damage. This scavenging action helps maintain the integrity of cell membranes and DNA.
- Enzymatic Defense:
- Endogenous antioxidants, including SOD, catalase, and glutathione peroxidase, work in tandem to convert harmful free radicals into less damaging substances, mitigating oxidative stress.
- Regulation of Cell Signaling:
- Antioxidants influence cellular signaling pathways, modulating inflammation and immune responses. This regulatory role contributes to overall health and disease resistance in animals.
Beneficial Roles of Antioxidants in Animal Health
- Immune System Support:
- Antioxidants bolster the immune system by protecting immune cells from oxidative damage. This support enhances the body’s ability to combat infections and diseases.
- Reproductive Health:
- Antioxidants play a vital role in reproductive health by safeguarding sperm and egg cells from oxidative stress. This is particularly crucial for fertility and successful reproduction in animals.
- Muscle Function and Performance:
- Antioxidants help maintain muscle integrity and function, especially in animals involved in strenuous activities or production processes. This contributes to overall performance and longevity.
- Neurological Health:
- Antioxidants support neurological health by protecting nerve cells from oxidative damage. This can have positive implications for cognitive function and overall mental well-being in animals.
- Aging and Longevity:
- By mitigating oxidative stress, antioxidants contribute to the overall healthspan of animals, potentially delaying the aging process and promoting longevity.
- Management of Chronic Conditions:
- Antioxidants may assist in managing chronic conditions, such as arthritis or metabolic disorders, by reducing inflammation and oxidative damage associated with these ailments.
Considerations for Antioxidant Supplementation
- Dietary Balance:
- A well-balanced diet that includes a variety of antioxidants is essential for optimal animal health. Different antioxidants work synergistically, providing comprehensive protection.
- Species-Specific Needs:
- Different animal species may have varying antioxidant requirements. Understanding the specific needs of each species is crucial for effective antioxidant supplementation.
- Environmental Stressors:
- Animals subjected to environmental stressors, such as heat, pollution, or intense physical activity, may benefit from increased antioxidant support to counteract the elevated oxidative stress.
Conclusion
Antioxidants are indispensable contributors to animal health, playing a vital role in protecting cells and tissues from the damaging effects of oxidative stress. Whether derived from endogenous production or obtained through a well-rounded diet, antioxidants offer a spectrum of benefits that extend from immune system support to reproductive health and beyond. As our understanding of the intricate interplay between oxidative stress and animal health evolves, the judicious use of antioxidants stands as a cornerstone in promoting the longevity, well-being, and disease resistance of animals in various settings. The antioxidant studies suggest that a wide range of natural and synthetic compounds possess antioxidant property. Most studies evaluating antioxidant properties have been conducted for short period under in vitro conditions. There is a need to determine the suitability of these products for in vivo application in terms of effective level of supplementation, interaction with other feed components, and effect on other biochemical parameters by taking some long term trials. Residual level of antioxidants in animal by–products like milk, meat and egg is another emerging field of livestock nutrition as antioxidant enrichment of food products as “Designer foods” is currently receiving much public attention with respect to their potential to promote better health.
Compiled & Shared by- This paper is a compilation of groupwork provided by the
Team, LITD (Livestock Institute of Training & Development)
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