What’s the Deal About Ethoxyquin?
by Dr Susan Orosz

Susan E. Orosz, Ph.D., D.V.M., Diplomate ABVP, Avian Practice, Diplomate, European College of Avian Medicine and Surgery, Professor. Dr. Orosz is a Professor at the University of Tennessee, Knoxville, specializing in Avian Medicine

The use of synthetic antioxidants in pet foods remains a controversial subject and represents an area that veterinarians need to understand. The most common of these synthetically derived compounds include ethoxyquin, butylated hydroxyanisole (BHA), and butylated hydroxytoluene (BHT). These compounds have been used in animal foods (including chicken diets) and in human foods as preservatives for more than 30 years. They play an important role in the prevention of oxidative rancidity of fats, loss of protein quality, and deterioration of fat-soluble vitamins.

So, why are we concerned about these antioxidants now? Because they “could” be bad. Concerns have been raised about these synthetic compounds contributing to cancer and chronic immunosuppressive disorders. Although they increase the toxicity of other chemicals, the concerns for ethoxyquin have not been documented to date. The dose and length of exposure is an issue that must be addressed scientifically in a variety of animals, including birds. On the other hand, it is known that colonies of research psittacines have been fed diets containing ethoxyquin for 5-10 years with no ill effects.

How about natural antioxidants? Much interest has recently been generated about the use of “natural” antioxidants. “Natural” isn’t necessarily “better.” The term natural can be misleading in the manufacturing business. Intuitively, natural would suggest that it is “better.” But “natural vitamin E,” for example, represents the residue from soybean oil tanks. These naturally derived antioxidants include gamma and delta tocopherols, ascorbic acid, citric acid, and lecithin. Gamma tocopherol, however, has only 10% of the biological activity of the alpha form, leading to the question whether use of this product has any biological use as a viable antioxidant at all.

Ethoxyquin is used in pet foods more commonly than “natural” antioxidants because of its vastly superior ability to stabilize fats and vitamins in the diet. For example, when ethoxyquin was incorporated with mixed fats, it took 100 days to reach a concentration of 20 meq/kg of peroxide (a breakdown product of fats). When alpha tocopherol was used, the same concentration was reached in only 12 days. Similar data has been found in tests with vitamins. In sum, the protective effect of a natural antioxidant may be as little as one-tenth as a synthetic antioxidant. Unfortunately, many pet foods are sitting on the shelf for longer than 100 days and the activity of the natural antioxidants will be reduced or will have expired by the time of purchase and/or use. To compensate for this problem, vitamin E could be added; however, if large amounts are added, this may indirectly affect selenium and/or vitamin D metabolism.

Without the presence of antioxidants in foods, components within the food will degrade over time at various rates. The protective effect of antioxidants helps maintain the nutritional value of the food, reduces rancidity, and/or inhibits discoloring. Without this protective effect, the diet’s metabolizable energy is reduced, with less fatty acids, proteins, and vitamins available. The vitamins most sensitive to oxidation are the fat-soluble vitamins A, D, and E, as well as vitamin C and beta-carotene. As we know, reduction of these vitamins in birds can lead to an altered immune status, making them more susceptible to infectious diseases, cancer, and calcium/phosphorous imbalances (poor bone and egg shell development). A vitamin E deficiency in the growing bird can result in crazy chick disease and, in the adult bird, white muscle disease and/or exudative diathesis.

For the present, ethoxyquin can be an important component for stabilizing the diets of companion birds so that each bird receives maximal nutritional value from its food. Nutritional deficiencies may occur, most likely from the oxidative rancidity of the fats. This can be particularly significant in young, growing handfed chicks. Ethoxyquin does have a place in diet preservation. This information can help you to look objectively at these issues.

Copyright 2002 Susan Orosz