Preservatives used in dog food have been blamed for causing every one of these problems. The nutrient that is most susceptible to spoilage is fat. Canned dog food is protected from oxidation by its airtight storage, but dry food, even with modern packaging, must include preservatives to maintain quality and safety.
Preservatives can be either artificial or natural.
Both types work by preventing fat and other ingredients in the food from oxidizing. The preservative that has caused dog owners the most concern is ethoxyquin. Although ethoxyquin has been used in animal feed for more than 30 years, in the last nine years the FDA has received many consumer reports about health problems occurring in dogs that were fed ethoxyquin-containing foods. Although several studies have not shown any adverse effects from using ethoxyquin in dog food at approved levels, consumer concerns have triggered further investigation into the safety of this preservative. No reproductive abnormalities or other health problems occurred.