Old World Aviaries

Antioxidants and preservatives

Blake Hawley, DVM
Director of Education
Kaytee Products, Inc.

Antioxidants, which are typically considered under the general category of preservatives, are used to prevent the reaction of certain food constituents (primarily fat and oil or foods of animal origin, such as egg) with oxygen. This protective effect is necessary to prevent a food or diet from spoiling, becoming rancid or discolored. The use of antioxidants has occasionally been questioned by aviculturists, pet owners and retailers. This concern focuses on the question of safety and the necessity of antioxidants in processed foods.

Antioxidants serve several functions in a diet. Of most importance to long term health is preventing the formation of hydroperoxides and free radicals, compounds that damage the cell's structure and possibly result in neoplasia (cancer). Of short term concern, antioxidants prevent fat oxidation (rancidity). Rancidity creates off-flavors and off-odors which dramatically decrease palatability and food consumption. Antioxidants also prevent the destruction of several nutrients. They provide direct protection to a number of vitamins which are unstable to the effects of oxygen, and indirectly, they prevent nutrient destruction caused by rancid fat's highly reactive free radicals. Fat rancidity and vitamin destruction can occur very quickly without an appropriate antioxidant present.

Natural antioxidants such as ascorbic acid (vitamin C) and vitamin E or other related tocopherols are effective antioxidants but are relatively short lived when compared to the chemical antioxidants. Due to the realities of the pet food distribution system and the relatively low volumes and slow use of exotic bird foods, the time interval between manufacturing a product and feeding it may be beyond the effective life of a natural antioxidant. If the product could be produced, refrigerated and consumed within a few months, natural antioxidants may be practical. However, since this time frame cannot be guaranteed, it is prudent to use the more stable chemical antioxidants for this critical function.

The commonly used chemical antioxidants, butylated hydroxyanisol (BHA), butylated hydroxytoluene (BHT) and ethoxyquin, are all chemicals that research indicates could be potential carcinogens when fed to certain species at "extreme" levels. As with most chemical safety testing, the experimental chemical is tested at a number of dietary levels, including levels that are magnitudes above the recommended or practical inclusion rate. Even when it is found to be carcinogenic at excessive levels only, the material is reported as a potential carcinogen. The levels at which this might occur typically become obscured, and the risk is assumed to be present at any level. This is an invalid assumption, which can best be illustrated by the affects of selenium, an essential element in the body. A diet severely deficient in selenium results in a high incidence rate of cancer. By supplementing selenium at required levels, the incidence rate is minimized due to the increased antioxidant action provided by selenium and its enzyme counterpart, glutathione peroxidase. Interestingly, selenium levels of only 5 to 10 times its requirement will begin to once again increase the incidence of cancer. Therefore, if selenium is not used at proper levels because of its known carcinogenic properties, other forms of cancer will be allowed to proliferate due to an inadequate antioxidant system. This same phenomena is seen with chemical antioxidants because the compounds formed in their absence (hydroperoxides) are definite and extremely potent carcinogens.

Approximately 400 birds at the Kaytee Avian Research Center were maintained at FDA-approved levels of ethoxyquin (20% higher than the normal use level) for a period of 5 years with no unusual neoplastic activity observed. (In canines, one of the most ethoxyquin-sensitive species known, levels of approximately four times the approved use levels are required to induce cellular changes indicative of the onset of cancer.) Monitoring has been continued at the lower, recommended level for an additional 6 years (11 years in total) without any negative results. For the last 5 years, over 4,000 exotic birds (100+ species) have been fed recommended levels of ethoxyquin and been monitored (blood chemistry, CBC, etc.) by veterinarians at the Avian Research Center. Any mortality experienced in the flock has been specifically evaluated by histopathology for ethoxyquin-specific changes that will occur in liver tissue when toxic levels are present. To date, no ethoxyquin-related tissue changes have occurred, even in the 11 year feeding group. This is the only test ever conducted on ethoxyquin use in psittacine species and is now one of the longest and largest tests conducted in any species. There is no legitimate reason to believe that any of the commercial antioxidants are a significant risk compared to the risk of unprotected food products.

The Avian Research Center will continue to review and research the use of ethoxyquin and other preservatives to ensure the greatest safety and efficacy of all of its products. At this time, there is no evidence which indicates that the proper use of ethoxyquin is in any way harmful to birds or other pets. It is certain, however, that the effects of rancid or oxidized food products, or compounds produced in the absence of antioxidants, are far more harmful and pose a much greater threat to your pet's health than the federally approved antioxidants.


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