Contamination and Animal Feed

Mycotoxins: Produced by fungi grown on forages and grains that are stressed during the growing season, mycotoxins may also form during storage of grains due to ideal conditions (moisture and temperature) for fungi growth. Mycotoxin action levels have been established by the U.S. FDA for aflatoxins, vomitoxins (deoxynivalenol or DON), and fumonisins in several ingredients and finished feeds. Feed and feed ingredients above these levels can be considered hazardous and subject to recall. Other mycotoxins may be considered contaminants at levels reasonably likely to cause harm to animals or humans based on scientific research even without an FDA action level. One likely to have an established FDA action level in the future is zearalenone.

As an example, aflatoxin is a common mycotoxin found in corn. Levels greater than 20 parts per billion in a finished feed may create food safety risks for young animals. Unfortunately, FDA does not allow blending of grains to reduce the aflatoxin to an “acceptable” level, nor is there a recognized “detoxifier” by FDA for the mycotoxins. Some states allow blending of such products and a few allow ammoniation to destroy the aflatoxin, but these are for intrastate use only. Thus, the feed manufacturers must check incoming raw materials for mycotoxins to ensure the safety of its finished products. Mycotoxin testing is influenced by the type of animal being fed and the crops in which mycotoxins are most frequently associated. Most feed manufacturers also depend upon suppliers to monitor mycotoxins as a part of their supplier verification programs. Feed and feed ingredients above these levels can be considered legal adulteration. Many of the mycotoxin tests have high analytical variation, so firms should be careful in setting any “trigger” levels considerably above a FDA action level, as the tests may be as much as 50 percent below the actual level.

Medications: Medicated feeds are closely monitored by FDA through inspection of medicated feed mills. Good Manufacturing Practices are regulated through Title CFR 21 Part 225 current Good Manufacturing Practices for Medicated Feeds. Through inspections, the FDA ensures registered medicated feed mills comply with regulated requirements, which includes control of medicated additives to avoid potential cross-contamination and drug carryover into meat, milk, eggs, or fish. Medication testing plans, proper segregation and mixing procedures, records, and housekeeping are some steps manufacturers take to ensure compliance.

Pesticides: Although a potential hazard, pesticides are generally considered a low risk due to controls within industry. In 2011, FDA reported the results from a pesticide monitoring study, which included animal feed. FDA collected and analyzed 199 domestic and 131 imported animal feed samples for pesticides. No residues were found in 134 (67.3 percent) of the domestic feed samples and in 85 (64.9 percent) of import feed samples, and unacceptable residue levels by EPA and FDA were found in only two domestic feed samples and 17 imported feed samples. Ethoxyquin and malathion were the most frequently found contaminants and together accounted for 41.2 percent of all residues detected.Dimethyl Tetrachloro­terephthalate was the third most commonly ­de­tected residue (contributing 13.9 percent to the total) but was only found in import samples. Feed manufacturers tend to de­pend upon approved suppliers to control pesticide contamination through their own monitoring or preventive control programs.

Heavy metal: Also referred to as trace minerals, heavy metals are present in trace or ultra-trace amounts in the environment and may or may not be essential nutrients for animals. The metals can be classified into the following four major groups, based on their importance to animal health.

• Essential – copper, zinc, cobalt, chromium, manganese, selenium, iron (ferrous)—these metals are also called micronutrients and are toxic when fed in excess of the animal’s requirement.
• Non-essential – barium, aluminum, lithium, and zirconium.
• Less toxic – aluminum and tin.
• Highly toxic – arsenic, cadmium, lead, and mercury.

The highly toxic elements are frequently encountered in insecticides, fungicides, batteries, paints, gasoline additives, and phosphate fertilizers. Cadmium tends to represent the highest risk due to where contamination may occur within animal feed. Most cadmium comes from zinc smelters and from the sludge obtained from the electrolyte refining of zinc. Also, relatively large amounts of cadmium are found in commercial fertilizers containing phosphates. Levels as low as 1 parts per million cadmium may have undesirable effects. Incoming trace mineral sources containing zinc, or phosphate sources, that are susceptible to toxic heavy metals should be monitored by the supplier to ensure the potential hazard in controlled.