The FDA has finally signed off on  Monsanto’s ethoxyquin study, but  it’s a case of too little, too late to save ethoxyquin in the marketplace.

The five year study was undertaken at the height of the ethoxyquin controversy, and tested the antioxidant on dogs and several generations of puppies.

The results of the study show that ethoxyquin levels above the current tolerance in dog foods (150 parts per million) produced no adverse reproductive effects.

There was, however, an increase in a dark, reddish brown pigment in the liver of female dogs immediately after completing a 6-week lactation. The liver pigment was identified as protoporphyrin IX, a normal intermediate in the synthesis of heme.

Heme is the pigmented, iron-containing non-protein portion of the hemoglobin molecule. Heme binds and carries oxygen in the red blood cells, releasing it to tissues that give off excess amounts of CO2.This pigment was also associated with elevations in liver-related enzymes in the serum of a few animals.

During lactation, the female dogs consumed two to three times more food as a percentage of body weight than they did at a maintenance level. This increased food consumption likely contributed to the increased pigment deposition in the liver and in the elevated serum enzymes. This activity in lactating dogs may be reversible when food consumption returns to maintenance levels, but that’s a finding that must be further investigated.

The FDA’s Center for Veterinary Medicine (CVM) has requested that pet food manufacturers voluntarily lower the maximum level of ethoxyquin in complete dog foods to 75 parts per million, from the current 150 ppm. CVM believes that this will provide a greater margin of safety in lactating females and possibly in puppies.

The FDA is watching a study funded by the Pet Food Institute designed to show that ethoxyquin is an effective antioxidant at levels between 30 and 60 ppm in a complete dog food. If the study shows that ethoxyquin works just as well at lower levels, the FDA will consider further action.

In the meantime, the proof is in that ethoxyquin really is safe in the amounts used in dog foods (usually much less than what’s allowed). Because a few manufacturers scared dog breeders and the public with unfounded rumors of hazards, the pressure has been on to eliminate ethoxyquin from pet food.

It’s still one of the best antioxidants around–cost effective and many times more effective than vitamin E at scavenging free radicals that can harm your dog.

But the marketplace has spoken. Most pet food companies have ditched it, with Hill’s® Science Diet® being the most notable exception.

Ross Becker, 1998

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