RG-8 Regulatory Guidance:
Contaminants in Feed (formerly RG-1, Chapter 7)

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Table of Contents

Section 1: Mycotoxins in Livestock Feed

Certain moulds are known to produce toxins in grain such that the suitability of the grain for use in livestock feed may be affected.

Feed manufacturers are reminded of their responsibilities under Section 3 (3) of the Feeds Act with respect to the production of feeds that are safe for livestock.

Fact Sheet - Mycotoxins

L.L. Charmley and H.L. Trenholm, AgReTech

Introduction

Mycotoxins are secondary metabolites produced by a variety of moulds on several agricultural commodities under specific environmental conditions. It has been estimated that at least 25% of the grain produced each year worldwide is contaminated with mycotoxins. In temperate climates such as Canada, the mycotoxins of major concern are the trichothecenes (including deoxynivalenol (DON), nivalenol (NIV), T-2 toxin and HT-2 toxin), zearalenone (ZEN), the fumonisins (FB) predominantly fumonisin B1 (FB1), the ochratoxins, predominantly ochratoxin A (OA), and ergot. However, aflatoxins (AF) are of concern in food and feedstuffs imported from warmer tropical and subtropical regions. Canada's indigenous mycotoxins occur mainly in cereal grains and corn, although occasionally there have been reports of contamination of other crops such as alfalfa and oilseeds, and foods such as coffee, cocoa, rice, beer and wine. As analytical techniques evolve to become more sensitive and widely available, the documentation of widespread contamination in a variety of commodities and of new mycotoxins no doubt, will increase.

Toxic Effects on Humans and Animals

Most toxicity studies deal with ingestion of contaminated food and feeds, but inhalation and skin exposure may also cause signs of toxicity.

The toxicology of many mycotoxins, particularly those commonly encountered, has been well documented for several animal species including humans. The signs of the many mycotoxicoses are diverse, numerous and often dependent on species, sex, age, stress, reproductive and health status of the animal. They include: feed refusal and vomiting DON (DON); impaired reproductive function and reduced fertility (ZEN, DON, T-2 toxin); nephrotoxicosis (OA, FB); neurotoxicosis (FB); lung disease (FB); hepatotoxicosis (FB); cancer (AF, OA, FB), and death (AF, T-2 toxin, FB, OA). Research has demonstrated subtle effects of mycotoxin contamination, including reduced immune function with compromised resistance to infection and disease (DON, AF, OA), and reduced animal performance (DON, AF, T-2 toxin, OA). The former condition increases the likelihood of transmission of pathogens such as Salmonella into the food chain. Recently FB was found to inhibit sphingolipid biosynthesis, which is thought to be a sensitive indicator of exposure to dietary FB contamination.

If a livestock species that is tolerant to a particular mycotoxin is fed a contaminated diet, there is a potential for the "carry-over" of toxin into animal products, such as milk or meat, destined for human consumption. In addition, the by-products of certain food processes, have the potential for being highly contaminated with certain mycotoxins and may cause severe adverse effects if subsequently fed to a species particularly sensitive to the contaminating mycotoxin or toxins. In both these cases a certain degree of care and monitoring is required to ensure the safety of humans and animals.

Under natural field conditions, it is unlikely that mycotoxins occur in isolation and more commonly a combination of contaminants will be found. In addition, the combining of several commodities in the manufacture of feeds for livestock may result in the concomitant combining of different mycotoxins, and so exacerbate this problem. Some mycotoxins when combined elicit a synergistic effect and some have an additive action, on an animal's health or performance. The type of interaction incurred is determined not only by the particular mycotoxin combination, but also the animal species involved. Moreover, an animal's response to mycotoxin-contaminated feed can be adversely affected by other factors such as nutrient availability, or deficiency, or environmental stressors (temperature, crowding etc.).

Prevention

Some management practices help to minimize mycotoxin contamination. These include:

  • Limiting bird and insect damage, because moulds tend to invade damaged kernels more easily than intact ones.
  • Harvesting grain as soon as possible. Fusarium mould grows readily under damp conditions.
  • Adequate drying and storage of grain to prevent mould growth and mycotoxin production post-harvest.
  • With high moisture corn, ensuring that ensiling conditions remain anaerobic to limit mould growth and mycotoxin contamination. Moulds cannot grow under truly anaerobic conditions.
  • Using crop rotation to minimize the carry-over of moulds from one year to the next.
  • Avoiding planting crops that may be susceptible to mould infestation in adjacent fields where the disease may spread from one crop to the other.
  • When contamination does occur, mould spores and mycotoxins are often concentrated in the fines and dust of grains. Use of masks to avoid inhalation and ingestion of dust by grain handlers is recommended,

A preeminent strategy for eliminating or reducing mycotoxin contamination is the development of pre-harvest host plant resistance to mould infestation and mycotoxin production in crops. Advances in this regard have been made to identify resistance to Aspergillus infestation and AF contamination, in corn, Fusarium infestation and DON contamination in wheat, and Fusarium infestation and FB contamination in corn. Genetic engineering strategies and the selection of hybrids naturally resistant to mould infestation and mycotoxin contamination are being studied in this regard. Promising results indicate that under some conditions, genetic engineering for insect and mould and mycotoxin resistance may enhance the safety of commodities such as corn, for animal and human consumption.

Under the Canadian National Feed Inspection Program, approximately 300 samples are analyzed annually for DON, FB1, T-2, HT-2, diacetoxyscirpenol (DAS), ZEN, and OA. In addition, AF (mycotoxins never detected in Canadian crops) are monitored in corn imported from warmer, drier climates such as the southern USA. There is also a mycotoxin trace back program which is used to investigate mycotoxin outbreaks.

Action Levels

A comprehensive survey of worldwide regulations and guidelines, as they existed on several mycotoxins in various countries was published by the FAO (FAO Food and Nutrition Paper 81, 2003). Regulations and guidelines for recommended tolerances for several mycotoxins (Canada and USA only) are shown in Tables 1 and 2.

Canada has established regulations for AF levels in food and feeds, and guidelines for DON, and HT-2 toxin (see Table 1). Moreover, although, many countries have established regulations or guidelines to protect consumers from the harmful effects of AF in foods and feedstuffs, the maximum permissible levels vary greatly among countries as do the guidelines and/or regulations or lack thereof regarding other mycotoxins.

Several international agencies currently strive to achieve universal standardization of regulatory limits for mycotoxins. This is an extremely difficult task because many factors have to be considered when deciding on regulatory standards. In addition to scientific factors, such as risk assessment (exposure and toxicological data), and analytical accuracy, economical and political factors, such as the commercial interests of each country, and the constant necessity of a sufficient food supply also play a role in the decision-making process. The whole process is further complicated by the fact that action levels pertain to single mycotoxin contamination, but in reality, several mycotoxins often co-occur in a contaminated commodity which may necessitate different (lower) action levels. Measuring the toxicological effects of a variety of different mycotoxin combinations, as they occur in nature, is an enormous and probably impossible task, especially considering that there may be mycotoxins present that have not been elucidated as yet. In addition, nutritional, management, environmental, and species effects all play a contributory role in determining the effect of a combination of mycotoxins on animal and human health.

Nevertheless, despite these obstacles most countries within the European Union have come to a common agreement on a standardized policy for regulation of AF levels in different feedstuffs and feedstuff ingredients (FAO Nutrition Paper 81, 2003).

A universal standard for total AF in foodstuffs of 15 µg/kg was suggested. However, countries with more stringent controls, based on the carcinogenic potential of these toxins, would be unlikely to agree with this level. Difficulties associated with enacting such legislation stem from analytical inadequacies regarding reproducibility of results, homogeneous and representative sampling and laboratory expertise.

The ideal goal is to eliminate mycotoxins from the food chain. However, on the practical level, this is not possible. The tolerance levels summarized in Tables 1 and 2 offer guidelines, based mainly on studies of individual toxins. Further research into the interactions of mycotoxins with each other and with other environmental and nutritional factors will enable validation and modification of these guidelines.

Detoxification

Mycotoxin contamination may be higher in grain dust and the lighter, shrivelled kernels. Thus, contamination may be reduced by density segregation to remove dust and the lighter, more highly contaminated kernels. Soaking, dehulling, or high velocity air cleaning of kernels can be used to remove surface contamination. Roasting may reduce mycotoxin contamination by burning surface contaminants and removing volatile, heat labile toxins and other mould metabolites.

Other approaches to reducing mycotoxin concentrations and effects on the animal are: improving the nutrient density of the feed; avoiding feeding contaminated commodities to sensitive animal species.

Table 1. Legislated maximum tolerated levels of aflatoxins, and regulatory guidelines of other mycotoxins in some foodstuffs, feedstuffs, and dairy products. From "Worldwide regulations for mycotoxins. FAO Food and Nutrition Paper 64, 1997."
MycotoxinsCommodityCanadaCommodityUSA
Deoxynivalenol (mg/kg) Uncleaned soft wheat for human consumption 2 Finished wheat products 1
Deoxynivalenol (mg/kg) Diets for cattle & poultry 5 Grains and grain by-products destined for ruminating beef and feedlot cattle older than 4 months and chickens (not exceeding 50% of the cattle or chicken total diet) 10
Deoxynivalenol (mg/kg) Diets for swine, young calves, & lactating dairy animals 1 Grains and grain by-products (not exceeding 40% of the diet) 5
Deoxynivalenol (mg/kg) Grains and grain by-products destined for swine (not exceeding 20% of the diet) 5
HT-2 toxin mg/kg (ppm) Diets for cattle & poultry 0.1
HT-2 toxin mg/kg (ppm) Diets for dairy animals 0.025
Aflatoxins µg/kg(ppb) Nut products for human consumption 15 All foods 20
Aflatoxins µg/kg(ppb) Animal feeding stuffs 20 Dairy products (AFM1) 0.5
Aflatoxins µg/kg(ppb) Feedstuff ingredients 20
Aflatoxins µg/kg(ppb) Cottonseed meal intended for beef cattle, swine or mature poultry (regardless of age or breeding status) 300
Aflatoxins µg/kg(ppb) Corn and peanut products intended for breeding beef cattle, swine or mature poultry 100
Aflatoxins µg/kg(ppb) Corn and peanut products intended for finishing swine of 100 lbs or more 200
Aflatoxins µg/kg(ppb) Corn and peanut products intended for finishing beef cattle 300
Table 2. Recommended tolerance levels (mg/kg) of several mycotoxins in Canada and the USA.
MycotoxinCanada: Recommended tolerance levelsUnited States Guidelines
Diacetoxyscirpenol (DAS) Swine feed <2
Poultry feed < 1
T-2 toxin Swine and poultry feed < 1
Zearalenone (ZEN) Gilt diets < 1 - 3
Cow diets 10 (1.5 if other toxins present)
Swine industry has voiced concern over levels of 0.25 - 5 in diets for sheep and pigs.
Ochratoxin A (OA) Swine diets (kidney damage) 0.2
Swine diets (reduced weight gain) 2
Poultry diets 2
Ergot Maximum alkaloid content in feed of:
Cattle, sheep, horses 2-3
Swine 4 - 6
Chicks 6 - 9
Fumonisin Animal FeedsTable note 1
Total ration in feed for horses and rabbits, 1
Total ration for pigs, 10
Total ration for cattle, sheep and goats more than 3 months old, 30
Total ration for ruminant and poultry breeding stock, 15
Total ration for poultry fed for slaughter, 50
Human FoodsTable note 2
Degermed dry-milled corn products, 2
Dry milled corn bran, 4
Cleaned corn, for masa, 4
Cleaned corn for popcorn, 3

Table notes

Table note 1

From Center for Veterinary Medicine/Food and Drug Administration Draft report, February 24, 2000.

Return to table note 1 referrer

Table note 2

From Center for Food Safety and Applied Nutrition/Center for Veterinary Medicine, Food and Drug Administration, November 9, 2001.

Return to table note 2 referrer

Contact

Feed Program
Canadian Food Inspection Agency
59 Camelot Drive
Ottawa, Ontario
K1A 0Y9

References

Charmley, L.L., and Trenholm, H.L. March 2000. A Review of Current Literature on Mycotoxins and Their Regulations. (Unpublished review for Canadian Food Inspection Agency, Government of Canada).

Charmley, L.L., Trenholm, H.L., and Prelusky, D.B. 1995. Mycotoxins: their origin, impact and importance: insights into common methods of control and elimination. In: Biotechnology In the Feed Industry, Proceedings of Alltech's Eleventh Annual Symposium. T.P. Lyons and K.A. Jacques (Eds) pages 41-63.

Charmley, L.L. and Prelusky, D.B. 1994. In: Mycotoxins in Grain. Compounds Other than Aflatoxin. Miller, J.D., and Trenholm, H.L. (Eds) Eagan Press, St. Paul, MN, USA pages 421-435.

Plant Products Division, National Feed Inspection Programs, 1996-1997 (1-3-93).

Trenholm et al., 1982. Vomitoxin and Zearalenone in animal feeds. Agriculture Canada Publication 1745E.

Trenholm et al., 1988. Reducing mycotoxins in animal feeds. Agriculture Canada Publication 1827E.

Underhill, L. 1996. Fact Sheet Mycotoxins. Mycotoxin Inspection Program, September, 1996.

Section 2: Action Levels for Dioxins, Furans, Dioxin-like polychlorinated biphenyls (PCBs) and Total PCBs in Livestock Feed

The CFIA regularly monitors livestock feed for environmental contaminants which have the potential to impact the safety of the food chain and the health of animals. Beginning in 1998, different types of livestock feeds and feed ingredients were surveyed to determine the levels of dioxins, furans, and PCBs. It has been estimated that food is the major source of human exposure to dioxins, furans, and PCBs, with 90 per cent being contributed by foods of animal origin (Fürst, Beck, and Theelen, 1992). Estimates also indicate that 80 per cent of these contaminants found in animal products originate from livestock feeds. Based on initial survey results and a review of the scientific literature, fish meals, fish oils, fish feeds, and mineral ingredients were considered to be potential sources of these contaminants and, as such, have been targeted for regular monitoring as part of the "Dioxin, Furan, and PCB Monitoring Program". The sampling results have been compiled to assess the background levels of dioxins, furans, and PCBs.

Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs), which are often referred to simply as "dioxins", are formed during the manufacture of chlorinated hydrocarbons, and so may be present as contaminants in PCBs, organochlorine pesticides, and phenoxyacid herbicides. Bleaching processes using elemental chlorine can also lead to the formation of dioxins. In addition, they are produced when organic matter is burned in the presence of chlorine, and are therefore found in fly ash from incinerators and produced naturally in forest fires. PCDDs and PCDFs are highly persistent in the environment, and are considered ubiquitous environmental contaminants. They can be found at very low levels in all living organisms and are able to bioaccumulate in food chains due to their lipophilic characteristics.

Depending on the degree of chlorination (1 - 8 chlorine atoms) and the substitution pattern, one can distinguish between 75 PCDDs and 135 PCDFs, called "congeners". The toxicity of dioxin congeners varies considerably. Of the 210 congeners, only 17 are of toxicological concern, and the analysis for "Total Dioxins" conducted by the CFIA is based on the combined concentration of these 17 dioxin and furan congeners. Exposure levels or residues are expressed in toxic equivalents (TEQ) of the most toxic congener, 2,3,7,8-tetrachloro-dibenzo-p-dioxin (2,3,7,8-TCDD), which allows the comparison of analytical results.

The International Agency for Research on Cancer (IARC) has classified 2,3,7,8-TCDD as a Group 1 carcinogen, which indicates that it is carcinogenic to humans. Effects seen in experimental animals include endometriosis, developmental effects at the behavioural level, reproductive effects, and toxicity to the immune system. The biochemical and toxicological effects following dioxin exposure are dependent on the tissue level, not the dose, and are therefore the same regardless of whether the intake is a large dose over a short period or a small dose over a long period.

PCBs are also considered to be persistent pollutants. PCBs differ from PCDDs and PCDFs in that they were intentionally manufactured for use in transformers, insulators, capacitors, etc., while dioxins and furans are produced unintentionally as unwanted by-products. PCBs consist of 209 different congeners and the analysis for "Total PCBs" conducted by the CFIA is based on the combined concentration of 72 of the 209 individual PCB congeners. Some of the 209 congeners, because of their chemical structure and biological activity, are considered to be "dioxin-like".

Twelve to 14 of the most toxic dioxin-like PCBs can also be expressed in toxic equivalents (TEQ). In 1977, the manufacture and import of PCBs was banned in North America, and the PCBs still used in electrical applications are currently being phased out.

Note: From this point in the section, the term "dioxins" will refer to dioxins (PCDDs), furans (PCDFs) and dioxin-like PCBs. The CFIA calculates total dioxins, including dioxin-like PCBs, using the international standardized reporting method of WHO-TEQ (World Health Organization - Toxic Equivalency) with the appropriate 1998 WHO Toxic Equivalency Factors (Van den Berg et al., 1998). This method includes seven dioxin congeners, 10 furan congeners and 12 dioxin-like PCBs. All of the data and action levels (except for total PCBs) in the remainder of this section are expressed using the WHO-TEQ terminology.

Acceptable analytical methods generally include a clean-up/extraction system (liquid-liquid extraction or Soxhlet extraction) and the use of gas chromatography with high resolution mass spectometry. This is the method used by the CFIA laboratory for the analysis of samples. The XDS-CALUX® EPA method #4435 has been reviewed and is an acceptable screening method for minerals. If other methods of analysis are used, the methods must first be reviewed by the CFIA laboratory to determine if the results are acceptable.

Based on the data obtained from sampling as part of the Monitoring Program, action levels have been set for total dioxins in: fish meals; fish oils; fish feeds; and minerals, mineral complexes, macropremixes, and anti-caking agents (see Table 3). Also, based on sampling results, the CFIA has reassessed its Action Level for Total PCBs in marine oilsTable note 3 used as a livestock feed ingredient (see Table 4). 

These action levels are considered interim levels. In the future, these action levels may be lowered, in an effort to continually reduce unnecessary sources of contaminants in foods of animal origin. This approach is consistent with the CFIA's policy of identifying and eliminating sources of contaminants in the food chain.

Feed manufacturers are reminded of their responsibility to produce feeds which are safe for all classes of livestock and to prevent the introduction of contaminants into the food chain via food of animal origin.

Table 3. Summary of Action Levels for Total Dioxins, Furans, and Dioxin-like PCBs (ng WHO-TEQ/kg) for Different Livestock Feed Ingredients.
Livestock Feed Ingredient Action Level
(ng WHO-TEQ/kg)
Fish Meal 3
Fish Oil 16
Fish Feed 6
Minerals, Mineral Complexes, Macropremixes,
and Anti-caking Agents
1.5
Vegetable Oils

For example:

  • Vegetable (palm) oil
  • Hydrogenated vegetable (palm) oil

By-products of Vegetable Oil Manufacturing

For example:

  • Calcium salts of fatty acids
  • Fractionated palm fatty acid distillates
  • Hydrogenated palm fatty acid distillates
  • Palm palmitic acid (C16:0)
0.75 (dioxins and furans only)
1.5
Table 4. Action Level for Total PCBs (mg/kg) for marine oils.
Livestock Feed Ingredient Action Level
(mg/kg)
Marine Oils 0.3

Table notes

Table note 3

For the purposes of this section, marine oils are defined as oils from approved marine sources (e.g. fish oil, mollusc oil), listed in Schedules IV and V of the Feeds Regulations.

Return to table note 3 referrer

References

Fürst, P, Beck, H., and Theelen, R.M.C. Assessment of human intake of PCDDs and PCDFs from different environmental sources. Toxic Substances Journal, 12:133-150, 1992.

Van den Berg et al., Review: Toxic Equivalency Factors (TEFs) for PCBs, PCDDs, PCDFs for humans and wildlife. Environmental Health Perspectives, 106:775-792, 1998.

Fact Sheet - CFIA Advises Not to Use Chemically-Treated Wood Near Livestock Feed and Animals

The Canadian Food Inspection Agency (CFIA) is advising livestock producers across Canada not to use chemically-treated wood structures near livestock feed or food-producing animals because they can transfer potentially harmful levels of chemicals into animal products, such as meat, milk and eggs.

As part of the CFIA's residue monitoring program, dioxin levels higher than background were detected in raw milk from two British Columbia dairy operations. The dioxin was found at levels that are not considered an immediate health risk by Health Canada. The levels found did, however, trigger follow-up action to identify and eliminate the source of contamination, in line with Canada's approach to managing dioxin in the food supply. Dioxins are released into the environment through natural and industrial processes and are commonly found in low levels throughout the food chain around the world.

The investigation indicated that chemically-treated wood used in some silage bunkers (animal feed containers) may, in large part, be the source of the dioxin detected. Exposure to wood treated with chemicals, such as pentachlorophenol (PCP), has been shown to result in higher than background levels of dioxins in livestock feed, which can then transfer into animal products. Further follow-up after precautionary measures were implemented indicated lowered levels of dioxin.

Producers should ensure that livestock feed is not stored where it can come into direct contact with chemically-treated wood structures. Animals should also not be allowed to come into contact with chemically-treated wood, including sawdust or shavings that could be used for bedding. At a minimum, bunker silos containing this wood should be lined with a plastic tarp and untreated lumber. Gloves should be worn when handling any treated wood and scraps must be disposed of in accordance with provincial/territorial and municipal regulations.

Section 3: Gentian Violet for Use in Livestock Feeds

The Animal Feed Division has reviewed the safety of gentian violet when used in livestock feeds.

Based on the information available, it has been decided to revoke the approval of this ingredient. The information reviewed did not satisfactorily substantiate the safety of gentian violet when used at 4 ppm in livestock feeds.

Since gentian violet will be removed from our list of acceptable ingredients for use in livestock feed, registration of all products containing gentian violet are cancelled. Regulatory action will be undertaken if gentian violet is found in the marketplace after June 30, 1992.

Section 4: Metal Contaminants

The CFIA regularly monitors foods and livestock feeds for contaminants which have the potential to impact the safety of the food chain and the health of animals. Livestock feeds and feed ingredients are monitored for the presence of metal contaminants because these contaminants may be harmful to livestock and humans.

Metals are elemental chemicals found naturally, to varying degrees, in the environment, feeds, and foods. They are also used in many industrial processes, including feed ingredient manufacture. In their elemental state, metals cannot be metabolised or destroyed; therefore, livestock that consume metal-contaminated feeds could accumulate these contaminants in their tissues over time. Contaminated animals could then transfer the metal to their offspring, the animal feed chain, the environment, or to foods of animal origin. Even trace amounts of certain metal contaminants may result in unacceptable tissue residues in foods for human consumption (e.g., meat, milk or eggs). Furthermore, feeds with high metal loads pose a human health hazard to those individuals working with, or otherwise exposed to, the product.

Sampling

All feed types can be sampled for metal contamination as part of the National Feed Inspection Program. This involves random sampling of a variety of feed products, including complete feeds and feed ingredients. The focus has been on sampling mineral ingredients, premixes and mineral supplements, because metal contaminants are more likely to originate from these feed ingredients. Samples are randomly taken by feed inspectors at commercial feed mills, rendering plants, retailers of livestock feeds, and on farms.

Metal contaminants of concern and Action Levels

Metal contaminant residues of concern which are routinely analysed include aluminum (Al), arsenic (As), cadmium (Cd), chromium (Cr), lead (Pb) and mercury (Hg). Mercury is only monitored in fish by-products (i.e., fish meal, fish oil). Action Levels have been defined for aluminum, arsenic, cadmium and lead (See Table 5) and enforced by the Animal Feed Division for a number of years. Action levels have not been established for chromium and mercury; however, sample results for chromium and mercury are assessed on a case-by-case basis.

A feed Action Level is the level at which, if exceeded, a metal contaminant may present a health risk, due to the potential for metal toxicity or due to unacceptable residues in foods of animal origin. These levels were established to assist with product safety assessments (i.e., identification of possible sources of contamination and appropriate corrective actions); and to facilitate industry compliance. These levels are based on the total livestock diet and not based on individual minerals.

Table 5: Action Levels for metal contaminants in total livestock diets on an "as fed" basis, including feeds and forages.
Metal Contaminant Action LevelTable note 4 Reporting Limit/
Limit of Quantification
Aluminum (Al) non-ruminant: 200 ppm

ruminant: 1,000 ppm

3.2 ppm
Arsenic (As) ppm 5.2 ppm
Cadmium (Cd) horses: 0.2 ppm

other livestock: 0.4 ppm

0.05 ppm
Lead (Pb) ppm ppm

Table note

Table note 4

Equals the maximum level for the metal contaminant in total livestock diets.

Return to table note 4 referrer

Compliance and Calculations of Interest

A product sampled for metal contaminants is considered acceptable if the metal contaminant is found at a level below the Action Level. The Action Level is set for total diets, therefore, in cases where the product is not a total diet (i.e., where it needs to be mixed with another feed, diluted, or mixed with forage), calculations must be done to determine the concentration of the metal in the total diet. If the ingredient may be added to multi-species feeds, then the highest suggested inclusion rate should be considered as the worst-case scenario.

Example calculation – acceptable:
Monogastrics (swine, poultry) Horses and ruminants (cattle, sheep, goats)
Lab result for Cadmium (Cd) in a premix: 3.6 ppm 3.6 ppm
Inclusion rate of premix in complete feed: 5% 5%
Inclusion rate in total diet (50% forage): n/a 50%
Level of Cd in total diet: 0.18 ppm
(= 3.60×0.05)
0.09 ppm
(= 3.60×0.05×0.5)

Decision: the calculated level of Cd for monogastric, horse, and ruminant diets is below the Action Level for Cd for horses (0.2 ppm) as well as all other livestock species (0.4 ppm), so this product is acceptable.

Example calculation – not acceptable:
Monogastrics (swine, poultry) Horses and ruminants (cattle, sheep, goats)
Lab result for Cadmium (Cd) in a premix: 15.0 ppm 15.0 ppm
Inclusion rate of premix in complete feed: 5% 5%
Inclusion rate in total diet (50% forage): n/a 50%
Level of Cd in total diet: 0.75 ppm
(= 15.00×0.05)
0.38 ppm
(= 15.00×0.05×0.5)

Decision: the calculated level of Cd for both monogastric and horse diets exceeds their Action Levels for Cd (0.4 ppm and 0.2 ppm respectively), so this product is not acceptable for monogastrics or horses. However, the calculated level of Cd for ruminant diets is below the Action Level for Cd (0.4 ppm), so this product is acceptable for ruminants.

Feeds that exceed the Action Level for any metal should not be fed to livestock. This approach facilitates the identification and elimination of contaminant sources in human foods and livestock feeds.

Feed manufacturers and producers are reminded of their responsibility to source ingredients from suppliers who have demonstrable records/systems in place to ensure ingredient safety. This will help promote the production of feeds that:

  1. are safe for all classes of livestock, and
  2. will not result in harmful tissue residues in livestock or animal products destined for human consumption.
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