Antioxidants and the Immune System

by Richard Goings, Ph.D., Dairy Specialist

The manager of today's dairy herd faces many challenges. Nutrition has primarily focused on forage quality, dry matter intake, and the various protein and carbohydrate fractions. Nutritional guidelines for many of the "minor" nutrients have usually been based on levels to prevent deficiencies, not overall health or optimum performance. Research demonstrating value for these minor nutrients requires very large numbers of cows and is confounded by many other factors. The current high cost of replacements has renewed interest in cow health and longevity and could justify special supplementation. Increasing nutrient levels will provide for increasing physiological performance. This article will cover the various trace minerals and natural antioxidants the cow uses to thrive.

Oxidation is a chemical process whereby an element or compound acquires a positive electrical charge, usually by reaction with an oxygen-containing molecule. The best-known example is the rusting of iron. Animal cells produce various oxidizers during their work. Also as the immune system kicks in, oxidizers are produced in killing the "invaders." If allowed to accumulate, these oxidizers or free radicals will damage or destroy the cell. Metabolic disorders that are linked to oxidizers include: mastitis, retained fetal members, and udder edema. The body has access to various antioxidants (Table 1) that act as sacrificial chemicals (rust preventers) that are easily oxidized, thus protecting more valuable oxidizable compounds like proteins, DNA, etc.

Vitamin E 

• main function is as an antioxidant
• generally low in most feeds except fresh forage
• supplementation is required and research continues to show responses to higher levels
• works closely with selenium; not as effective when selenium is deficient 
• injection of E is not as effective as feeding

Selenium

• critical component of glutathione peroxidase
• classic symptom of deficiency is white muscle disease in calves
• levels regulated by law because of potential toxic amounts and link to cancer
• injections can be effective
• FDA has approved selenium yeast as a feed additive

Copper 

• important to three dimensional structure of immunoglobins and white blood cell killing ability
• at high levels can act as a pro-oxidant

Carotenes

• a family of compounds; animals convert carotenes to vitamin A
• some evidence that carotenoids enhance pathogen killing activity independent of vitamin A

Zinc

• used in numerous enzymes including superoxide dismutase which neutralizes free radicals
• essential for skin integrity and building keratin

Manganese

•  little is known on its function in immunity but has been shown to affect antibody titers

Iron

• primary function is as component of hemoglobin in red blood cells
• constituent of catalase which acts mainly in the liver to convert free radical peroxides to water at high levels can act as a pro-oxidant negating vitamin E
• high levels appear to influence udder edema (Table 2)
• feed and/or water are often high in iron 

Ascorbic Acid/Vitamin C

• a major antioxidant inside cells
• feed sources are destroyed during rumen fermentation although stabilized forms have some rumen by-pass
• may also function to restore radical scavenging activity of vitamin E

Summary

All animals require oxygen for life, but oxygen is also an extremely reactive and toxic element. During normal cell processes, environmental insults and/or inflammatory responses, cells produce compounds called reactive oxygen species or free radicals. The body has developed a sophisticated antioxidant system to neutralize these free radicals with various trace minerals and vitamins critical to this function. The cow at calving is particularly vulnerable to oxidative stress perhaps due to transferring trace minerals, vitamins and immunoglobins to colostrums. Supplementation of antioxidants nutrients is usually necessary.

For more information please call us at 1-800-553-1712 or email us at contactus@vigortone.com. You can reach Dr. Goings at rgoings@vigortone.com.