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From: Food Quality & Safety magazine, June/July 2014

Contamination and Animal Feed

Controlling potential contaminants to protect the food of livestock and pets

by Henry Turlington, PhD

Rounding Up Contamination

Today’s consumers are very interested in the safety of our food supply. They also show a growing concern when it comes to the food supply provided to the livestock our farmers and ranchers raise, and even more, animal food available to their pet family members in their own homes.

Over the years, several high-profile events have raised the awareness of animal food safety that spotlighted the risks to our food chain. The bovine spongiform encephalopathy outbreak in the 1990s, better known as BSE, and the melamine contamination in pet food in 2007 are two well-known and publicized past events in the industry. Although rare, these events still gain the public’s attention; but in fact, many more million tons of feed is manufactured safely each year.

Last year, there was more than 150 million tons of animal feed manufactured by 6,700 feed mills in the U.S. This does not include more than 8 million tons of pet food manufactured in the U.S. These animal feeds required multiple raw materials mostly from crops grown within the U.S. or Canada.

Many of the ingredients used by the animal feed industry are materials not used for human consumption or are products remaining after processing materials for human food, known as co-products for animal feed. This includes materials such as bakery byproducts, dried distillers grains (from beverage and industrial ethanol production), soybean and cottonseed meals and hulls (from vegetable oil processing), molasses (from sugar production), and peanut skins.

In addition, most animal feeds are manufactured as complete diets for animals and fed as the sole food for animals. Thus, the type of animal and the animal’s life stage impacts the nutritional fortification of the feed to ensure the animal’s needs are provided.

There have been almost 500 recalls of animal foods from 2013 to the present. Of these recalls, 95 percent were pet products, primarily due to suspected Salmonella contamination or risk (89 percent). With the majority of pet foods fed within the home, microbial contamination is a major concern for the industry to ensure the safety of the pet owners. For livestock, such as cattle, poultry, and pigs, Salmonella contamination is not as worrisome of an issue, as the feeding environment and the feed processing do not pose a food safety risk for humans.

Industry is faced with a variety of potential contaminants within animal feed, mostly the contaminants come from incoming materials. It is important to assess the severity and probability of the potential contaminations in order to determine the actions required, if any, to control the potential risk. The principles of Hazard Analysis and Critical Control Points, or HACCP, program are useful in order to manage the potential risks from contamination, which can be divided into physical, chemical, and biological risks.

Major Classes of Mycotoxins, Common Food Products that may be Contaminated and Animals that are Most Affected
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Major Classes of Mycotoxins, Common Food Products that may be Contaminated and Animals that are Most Affected

The Risks

Physical. Bulk materials are the most common source of physical contamination. Proper inspection prior to unloading is the first step in minimizing the risk of contamination. A bulk material may be transported several times (harvest, rail, truck, etc.) before reaching a feed mill for processing into animal feed. Thus, materials are screened to remove debris that does not belong in the ingredient and may have been introduced during transport. Magnets are used to remove ferrous materials throughout the manufacturing process, including during receiving. Most physical contaminants do not create food safety risks for the animal or humans.

Chemical. The highest potential risks for animal food safety come from chemical contamination. The most common risk is mycotoxins, which form naturally within grains.

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.

Raw Materials Used in Feeds
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Raw Materials Used in Feeds
Raw Materials Used in Feeds
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Potential Contaminants in Animal Feed

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.

Dioxins: ­Polychlorinated byphenyls (PCBs) or dioxins, many considered to be carcinogens when fed for extended periods, have been identified as a potentially hazardous risk for animal feed. In 1997, FDA found contamination of animal feeds with dioxin, which resulted in elevated levels of dioxin in chickens, eggs, and catfish. The source of the dioxin contamination was traced to a mined clay product called “ball clay,” which is used as an anticaking agent in soybean meal, other feed components, and complete animal feeds. As ball clay in this episode was an occasional ingredient, the industry and ball clay suppliers asked for its removal from the Association of American Feed Control Officials’ Official Publication, thereby precluding its use again, as state law utilizes that publication as the official list of approved ingredients.

Currently, there are no regulatory tolerances or action levels for dioxins or PCBs in animal feed. PCBs have become a persistent and omnipresent contaminant in the environment. As a result, certain animal feeds, principally those of marine origin, may contain PCBs at low levels. Nonetheless, feed manufacturers work with suppliers to ensure the potential risk is controlled.

Formulation: With most animal feeds provided as a complete diet, formulation of finished products is important to ensure the proper nutritional levels are supplied for the specific type of animal and life stage. It is important deficiencies or toxicities are avoided when formulating. Review of mixing records, proper mixing times, and testing of finished product are examples of the steps feed manufacturers take to ensure finished products meet expected specifications. Proper controls of manufacturing processes ensure finished products meet the desired specifications. Feed manufacturers must identify areas that are critical processes, and establish steps that ensure the safety of finished products.

Biological. Microbiological contamination of pet food is a human food safety risk due to the pet food feeding practices and potential exposure to people. In 2012, CDC reported that a multistate outbreak of Salmonella Infantis infections was linked to pet food. More than 20 people across 13 states were infected. The association between human outbreaks of salmonellosis and contact with Salmonella-contaminated pet food and pet treats is well established. FDA launched several pet food sampling programs in the past few years, but the most recent results from 2012 to evaluate the prevalence of Salmonella in pet food are still pending.

Potential Contaminants in Animal Feed
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Due to the potential hazards from microbiological contamination, pet food manufacturers must take steps to control the risk. This is done through manufacturing processes (segregation of manufacturing areas; stringent sanitation practices; personal flow), environmental monitoring, finished product testing (hold and release), and supplier verification programs. While such preventive controls are expensive, the potential severity and exposure of the hazard require it.

Biosecurity: For livestock feeds, microbiological contamination generally is not considered a human safety risk due to the feeding practices of animals and the lack of animal feed exposure to humans that could create a food safety risk. However, feed manufactures must control the potential risk for the spread of disease among livestock. As an example, feed manufacturers must establish stringent biosecurity practices to prevent the spread of Porcine Epidemic Diarrhea virus (PEDv) to pigs. This includes steps during manufacturing and transport to ensure the feed or transport vehicles are not contaminated from one farm to the next.

Moreover, FDA’s Compliance Policy Guide (690.800) entitled “Salmonella in Food for Animals” details eight serotypes of salmonellae in five species of feed that must be controlled. Otherwise, FDA says the feed may be deemed to adulterated and subject to recall if these salmonellae are discovered.

Total feed production by all mills - 2013
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Total feed production by all mills - 2013

Control of Contamination

The Food Safety Modernization Act (FSMA) focuses on food and feed safety practices. The multiple proposed rules are designed to improve the safety of foods for humans and animals. Most feed manufacturers already focus on controlling contamination hazards through their own animal food safety programs.

There are primarily three sources of contamination: incoming ingredients from suppliers, manufacturing processes, and delivery processes to the customer. The following steps are used to control contamination.

1. Supplier verification program. The potential for contamination is greater for incoming materials. Thus, feed manufacturers focus on controlling the risks from ingredients and their suppliers. Actions to control the potential risks from incoming ingredients may include onsite audits of the suppliers to learn more about the manufacturing processes for the ingredient and the suppliers’ food safety plans; testing programs for incoming ingredients to monitor quality and food safety; requirements for certificates of analysis of shipments for particular nutrients or contaminants to ensure specifications are met; and third-party certifications by the suppliers to ensure effective food safety programs are maintained.

2. Third-party certifications. With an increasing demand for quality and food safety, many feed manufacturers obtain third-party certifications for their feed manufacturing facilities to assure customers that proper processes have been developed and implemented for food safety. Systems are available today that are benchmarked against global standards, such as the Global Food Safety Initiative (GFSI), for animal feed and pet food production. American Feed Industry Association and SQFI worked together to provide the only global standards for animal feed and pet food that are benchmarked by GFSI: FSC 34 Safe Feed/Safe Food Certification and FSC 32 Pet Food Manufacturing Facility Certification.

3. Biosecurity practices. The delivery of finished products may pose a risk for spread of animal disease if proper biosecurity steps are not taken. Feed manufacturers implement stringent biosecurity practices for the delivery of feed to swine farms to prevent the spread of disease across farms, such as PEDv.

The control of potential contaminants is a key component for a successful animal food safety plan. The feed industry has worked closely with FDA to ensure regulatory requirements are met, and the animal food supply is safe for the intended animal and the humans that handle it. As the new requirements for FSMA are defined for animal food, the feed industry will work with FDA to achieve and maintain compliance in a timely fashion. This will take a number of years, as the law and its resulting rules are complicated and demand more processes, paperwork, and patience in the ensuing decade. In the meantime, feed manufacturers will continue to strive to maintain a high-quality and safe food supply for animals.


Dr. Turlington is the director of quality and manufacturing regulatory affairs at American Feed Industry Association. Reach him at hturlington@afia.org.

References Furnished Upon Request

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