Animal Products: Contributors to a Safe Food Supply FO-05513 1991 To Order Animal Products: Contributors to a Safe Food Supply P. T. Anderson, B. A. Crooker and M. M. Pullen Table of Contents Introduction Getting an Animal Product Approved: FDA's Role Monitoring the Meat Supply: FSIS I. Monitoring Program II. Surveillance Program III. Residue Avoidance Program IV. In-Plant/On-Farm Testing V. Federal Agency Cooperation Ensuring Safety of the Milk SupplyProduction Practices in American Animal Agriculture Use of Hormones to Improve Animal Production Bovine somatotropin Use of Antibiotics to Maintain Animal Health Relative Risk of Antibiotic Use Summary Suggested References Introduction A safe food supply is vitally important to all Americans. Data in Table 1 describe consumer concerns, although consumers' perceptions of relative risks do not always agree with the assessment of experts (Table 2). The Food and Drug Administration (FDA), and the U.S. Department of Agriculture, through its Food Safety Inspection Service (FSIS), assure that Americans have one of the safest food supplies in the world. American farmers and ranchers provide safe, wholesome, high quality food products at prices that are low compared with those in other countries. The safety of typical production practices, including use of some drugs and hormones to improve animal health and performance, has come under scrutiny recently. This publication discusses production practices of livestock producers, relative risk of animal products and the role of government agencies in food safety issues. Table 1. Consumer concern about selected food attributesItem% rating as a serious hazardChange 19871991 Pesticides, herbicides7680+4 Antibiotics, hormones6156-5 Fats5562+7 Cholesterol5158+7 Nitrite content3841+3 Salt content4332-11 Irradiated foods4342-1 Additives, preservatives3629-7 Sugar content2818-10 Artificial coloring2424— Food Marketing Institute (1991) Table 2. Evaluation of food-related risksRiskConsumer"Expert" Pesticide residues1*4 Food additives25 Environmental contaminants32 Pathogenic microorganisms41 Naturally occurring toxicants53 *1 ranked as most severe risk, 5 least Getting an Animal Product Approved: FDA's Role Back to Table of Contents Animal health companies cannot simply sell any compound they develop. FDA requires animal drug manufacturers to show that each new animal drug is safe and effective before it is approved for marketing. Manufacturers also must submit a reliable assay method for detecting drug residues in slaughtered animals. These analytical methods are reviewed by FDA before the drug is approved. FDA also sets tolerances for acceptable levels of residues of the drug in animal tissue. The tolerance includes a built-in safety factor to assure that the drug will have no harmful effects on consumers of the food. Typically, the safety factor that is used sets the illegal residue level at 100 to 1000 times less than a potentially harmful concentration. USDA regularly monitors tissue samples from slaughtered animals for over 100 chemical compounds. FDA requires that any agricultural chemical or drug be proven effective as well as safe for both animals and consumers. Specific approval criteria include: The product must be effective at the proposed dosage level for the proposed use. The drug must not create a residue in the edible tissue of the animal or bird that is at a level which is judged harmful to the consumer. The drug or agricultural compound must serve a useful purpose in the production of a feed crop, animal or bird. An analytical detection method must be available that is capable of detecting the substance at or below the tolerance level. The drug must be used in a manner that would not contaminate the environment or food supply. Monitoring the Meat Supply: FSIS Back to Table of Contents The primary goal of USDA's residue program is to protect consumers from adulterated meat and poultry products. I. Monitoring Program When meat is sold commercially, there must be federal inspection of each carcass. Animals slaughtered at federally inspected plants are sampled for illegal residue levels at random. This random sample produces a statistically valid national drug residue picture. Annually, approximately 22,000 animals are sampled under the monitoring phase. In many cases, three or more individual tissue samples (muscle, liver, kidney and fat) are taken from a single animal. Each tissue sample, in turn, is analyzed for one or more compounds. The basic approach is to sample each species at a rate that will detect a 1% incidence of illegal residues with an assurance of confidence of 95%. This requires 300 samples evenly spaced over the year. Variations are made in the sampling requirement based on specific information about the compound, species and potential risk. The prevalence of illegal drug residues reported by the National Monitoring Program is less than 1%. The Monitoring Phase serves several functions. Its primary purpose is to determine the incidence and trend of the various drug, pesticide, environmental and agricultural chemical residues in animal tissue. These findings serve as a basis for follow-up investigations by FDA to determine the causes of the illegal residues. To help livestock producers avoid exceeding FDA residue tolerances, FSIS notifies individual producers whenever a sample is between 80 and 100% of the tolerance. FSIS tests animals from subsequent herds or flocks to assure that residues in animals from that particular farm remain below legally permissible levels. Residue data also are evaluated to determine if special surveillance programs are necessary; if so, such programs are designed and implemented. For example, in 1977 unacceptably high rates of sulfonamide residue violations in swine led to a special program to significantly increase sampling for those residues. If an illegal residue is detected, FSIS reports the violation to FDA's field office and the Center for Veterinary Medicine. The field office then conducts an investigation. FDA investigators (or state officials in certain cases) visit the "premises of origin," that is, the farm or feedlot from which the animal went to slaughter. The investigation is aimed at determining the cause of the residue and identifying those responsible. Under FDA regulations, an animal containing an illegal residue is considered to be adulterated food the moment it leaves the premises of origin destined for a slaughter plant involved in interstate commerce. Results of the investigation can be used by FDA and FSIS in the second phase (surveillance) of the program to control illegal drug residues. Imported meat is also re-inspected and tested for residues at the port of entry. Countries exporting meat to the United States must have residue efforts comparable to the U.S. program. II. Surveillance Program The second part of the residue program, the surveillance program, uses a subjective sampling method. Animals are sampled under the Surveillance Program because they belong to producers responsible for recent illegal residues or because there is some indication, such as marks left by a drug injection, that the animal may contain illegal drug residues. Animals suspected of being sick or diseased also may be sampled under the Surveillance Program. Because this phase is obviously biased in its pattern, the residue figures are not representative of national prevalence; only the Monitoring Program figures can be used to show national rates of illegal residues. No matter in which phase of the program an illegal drug residue is found, FDA can conduct an investigation and FSIS will detain future shipments from the affected producer while tissue samples are analyzed. These shipments must be shown to be free of illegal residues before carcasses or parts are approved for food. III. Residue Avoidance Program Inaugurated in 1983, the Residue Avoidance Program is designed to help farmers identify points in their production systems where contamination could occur. Prevention of residues at all stages of production—from birth through slaughter and processing—is the goal of this program. This approach best serves the interests of both the food industry and consumers. The Residue Avoidance Program is an educational program designed to help producers better use and control drugs and chemicals, thereby avoiding costly violations in meat and poultry at slaughter. FSIS has enlisted the cooperation of the Extension Service and producer organizations in this effort. IV. In-Plant/On-Farm Testing The Swab Test on Premises (STOP) quickly tells an inspector whether antibiotics are present before a carcass leaves a plant. To conduct the test, cotton swabs are inserted into liver or kidney tissue and then incubated overnight on a bacteria-laden agar plate. If antibiotics are present, bacteria will not grow around the swabtip. If not, bacteria will grow uniformly on the plate and the inspector can approve the carcass. The Live Animal Swab Test (LAST) utilizes the same procedure to test urine. This allows livestock producers or veterinarians to test live animals to determine whether illegal antibiotic levels are present before shipping the animal to slaughter. The Sulfa-on-Site (SOS) test has made possible testing of large numbers of swine for sulfamethazine residues at the slaughter facility at low cost and within two hours. The SOS test is a visually observed test designed to screen swine serum, urine or feed for sulfamethazine. It may also be possible to establish some type of farm-based pre-slaughter testing program and/or some means to assure that swine presented for slaughter are not adulterated. FSIS scientists are working to perfect other on-farm tests to check feed and live animals for sulfonamides and antibiotics. V. Federal Agency Cooperation Agreements between three federal agencies—FDA, USDA and the Environmental Protection Agency (EPA)—outline their responsibilities in the residue monitoring program. These agencies also share information with appropriate state agencies. When necessary, the three agencies work with states to determine appropriate steps to correct a situation that results in excessive residues. All illegal residues in animals are investigated by FDA, or where there is an agreement with a state, by appropriate state officials. If pesticide residues are determined to be apparently due to direct applications or environmental contamination, the EPA regional office will work with FDA and FSIS to correct the problem. In either case, FSIS assumes primary responsibility for the wholesomeness of the food supply. EPA has responsibility to assure that pesticides are used according to label directions, and FDA has final authority for enforcement of the laws governing use of animal drugs and acceptability of medicated feeds. Thus, FDA and FSIS can seize or condemn contaminated food intended for human consumption. FDA may also seize animal feed. FDA may not take punitive action for first offenses, but may do so if intent or prior knowledge of a residue violation can be documented. Offenders face criminal prosecution with fines or imprisonment, as provided for under the law, if they are found guilty. Ensuring Safety of the Milk Supply Back to Table of Contents FDA is responsible for enforcing the Federal Food, Drug and Cosmetic Act, which requires that foods shipped in interstate commerce, including milk and milk products, be safe, clean and properly labeled. The agency's milk safety program is a collaborative federal/state effort that dates back to the mid-1920s. The Grade A Pasteurized Milk Ordinance (PMO), which was recommended by the Public Health Service (PHS) and FDA, is the standard used in the Cooperative State PHS/FDA Program for certification of Interstate Milk Shippers (IMS). Approximately 150,000 Grade A dairy farms and 800 Grade A pasteurization plants in all 50 states are covered by the IMS program. Under the PMO, state regulatory agencies are responsible for routine inspection and sampling of milk. Minimum estimates are that 1,200,000 milk samples and 70,000 milk product samples are tested each year. FDA further tests by spot-checking samples from hundreds of milk processing plants each year. Combined state and FDA records indicate that greater than 99% of all samples test negative. When a sample is found to contain antibiotics or other unnatural microbial inhibitors, the sale of that raw milk is immediately stopped. No milk or milk products may be sold until subsequent samples are found not to contain this type of contamination. Since each bulk tank of milk is sampled before it is picked up for processing, any indication of contamination can be traced back to the responsible farm and regulatory action taken. Additionally, the PMO requires that all dairy farms be inspected at least twice annually. All states are in compliance with this minimum and many inspect more frequently. As part of the farm inspection, the state examines the drug inventory to ensure that unapproved and/or improperly labeled drugs are not used and/or stored in the milkhouse, milking barn, stable or parlor. This helps to ensure proper drug use and residue avoidance by requiring that only appropriate drugs with adequate directions for use are present on the farm. Production Practices in American Animal Agriculture Back to Table of Contents Research has greatly improved our ability to maintain healthy animals and has increased our understanding of the controls that regulate growth and lactation of food producing animals. This knowledge has led to the development of products that can be used by livestock producers to produce meat more efficiently. All products that are used in production agriculture have been approved by FDA. Still, a concerned public has the right to ask whether use of these products in animal production is a safe practice. Use of Hormones to Improve Animal Production Back to Table of Contents Due to improvements in genetics, nutrition and management, U.S. beef production per cow has approximately doubled in the past few decades. One management technique that has contributed to this improvement is the use of hormonal growth promotants (implants). Natural or synthetic sex steroid implants are placed under the skin of the ears of young calves or feedlot cattle. Due to the low, constant blood supply to the ear, the implants release hormone at a constant rate over a period of 80 to 200 days, depending on the brand chosen. Implants improve growth rate and feed conversion efficiency 5 to 15 percent and also increase the amount of lean that the cattle gain, while decreasing rates of fat deposition. It has been estimated that use of anabolic implants results in an annual increase in production of 733,867,000 pounds of beef in the U.S. while saving 2,913,977 tons of feed. Typically, implants, which cost $1–2, return $10–15 to the beef producer for each dollar invested. Since most implants include estradiol or some other form of estrogen, consumers have questioned whether beef from implanted cattle contains levels of estrogenic activity that pose a health risk. Tables 3 and 4 include data on estrogen content in various tissues from implanted and nonimplanted steers and heifers. Implanting steers with 24–36 mg of estrogen activity does not significantly raise the estrogen content of muscle. Estrogen content of kidney and liver (the tissues that are involved in estrogen excretion) in implanted steers is raised to the levels found in unimplanted heifers. Removal of the implant 24–36 hours before slaughter will result in tissue estrogen levels below that of unimplanted steers. Estrogen levels in tissues from implanted heifers does not differ from levels in nonimplanted heifers. Table 3. Estrogen concentrations (pg/g) in tissues of heifers and steersSexMuscleKidneyLiver Heifer13.070.871.0 Steer12.526.027.6 Henricks, et al., 1983 Table 4. Mean tissue estrone (E1) and estradiol (E2) concentrations (pg/g) in control and implanted steers after 0 or 24-hour withdrawal (W/D)TissueControl0 h W/D24 h W/D E1E2E1E2E1E2 Muscle6148171513 Liver201457791642 Kidney fat231055544029 Henricks et al., 1983 Tables 5 through 8 put these estrogen values in perspective. Beef is simply not a great source of estrogen compared with many other foods or in relation to human estrogen production. In fact, according to the Council for Agricultural Science and Technology, "In a meal of mashed potatoes, whole wheat bread, green salad, green peas and ground round steak from estrogen-treated cattle, the food that would contain by far the least estrogenic potency is the ground round steak." The amount of estrogen in a 100 gram serving of beef, if 100 percent was absorbed (only 10 percent absorption would be expected), would be cleared from the bloodstream of a normal male in 3.6 seconds. The increase in estrogen exposure in humans due to use of growth implants in cattle is negligible. Zeranol, a synthetic compound that has estrogenic activity, is used in some growth implants. Because the chemical structure of zeranol differs from naturally produced estrogens, its presence can easily be detected in meat. In the past several years, zeranol content of hundreds of samples has been analyzed; zero violations were found. Table 5. Quantity of estradiol in beef muscle relative to human estradiol productionEstradiol clearance rate in normal humans (male or female)1250 ng/hour Estradiol content in 100 g of beef muscle1250 pg Time required to clear 1250 pg3.6 seconds Daily estradiol production in men25–60 micrograms Estradiol content in 100 g of beef muscle1250 picograms Quantity of beef muscle that would contain 30 micrograms of estradiol2,400,000 g (5,286 lb) Table 6. Human plasma estradiol concentration (ng/dl)DescriptionRange Children, men, post-menopausal women1 to 10 Women, cycling or early pregnancy10 to 50 Women in last third of pregnancyup to 150 Table 7. Estrogen levels in foodFoodEstrogen content (ng/g food)Estrogen content (ng/3 oz food) Steer beef, implanted0.0221.9 Wheat germ4340 Soybean oil2,000168,000 Milk0.13011.0 Syntex Agribusiness (1987) Table 8. Relative increase in human estrogen exposure due to consumption of beef from steers treated with a growth-promoting implant Increase FractionPercentage Children 5–60 days of age:—43,395,000 pg of estrogen produced daily —530 pg of additional estrogen from implanted steers1/81,877.0012% Women under 41 years of age at peak estrogen production:—540,000,000 pg of estrogen produced daily —530 pg of additional estrogen from implanted steers1/1,018,868.00010% Men—adult:—167,968,000 pg estrogen produced daily —530 pg of additional estrogen from implanted steers316,920.00032% Bovine somatotropin Proposed use of bovine somatotropin (BST) in dairy cattle has received much public attention. BST, a protein hormone, is produced in the pituitary glands of all cattle. When additional BST is administered to lactating cows, milk production is increased. Some consumers have expressed concern about BST use because they equate use of the hormone with increased hormone content of milk. All milk contains minute quantities of BST (generally less than 3 parts per billion). When cows are treated with BST, the amount of BST in milk is not increased. In fact, milk composition, flavor and processing qualities are unchanged when cows receive BST. FDA has utilized considerable amounts of information to determine that milk from BST-treated cows is safe for human consumption. First, BST is not active in humans. Only somatotropin from humans or other primates (monkeys, etc.) is active in humans. Second, BST is a protein and, just like insulin, it is not active when taken orally; it must be injected to be effective. Third, BST is a large protein and can not cross the intestinal wall in intact form. BST must be degraded to individual amino acids to be absorbed, and once degraded, is no longer active. Anyone who can safely consume milk can safely consume milk from BST-treated cows. FDA has not yet completed evaluation of the effect of BST on cows. However, more than 22,000 cows have been treated with BST and there is no indication that BST impairs the health of these animals. Use of Antibiotics to Maintain Animal Health Back to Table of Contents Antibiotics serve two purposes for livestock producers. As in humans, acute microbial infections in livestock species are treated with antibiotics, resulting in reduced animal suffering and death. A few farmers utilize sub-therapeutic antibiotic levels to maintain health in pigs, veal calves or poultry. Use of antibiotics in food production further benefits consumers, in that some organisms that are capable of transmitting disease to humans have been reduced or eliminated through this practice. Use of antibiotics is tightly regulated and withdrawal times are closely observed. Antibiotics are among the compounds that the National Monitoring Program focuses on. Table 10 illustrates that in 1989, 99.64 percent of all samples from livestock and 98.66 percent of all samples from poultry were below FDA limits for all compounds analyzed. Table 9. FSIS testing of meat and poultryYearNumber of samplesNumber of compounds tested for 198065,00083 1988327,000112 1989442,000120 Table 10. Results of the 1989 National Meat Monitoring ProgramCategoryNon-violative rate Livestock99.64% Poultry98.66% Results of analysis of milk samples also indicate less than 1 percent of all samples analyzed were in violation. However, random samples of milk taken off-the-shelf by the Center for Science in the Public Interest have been reported to contain illegal residues. These data were generated using an assay technique known as the Charm II test. The Charm II test is useful as a screening test, but is a non-specific technique designed for speed, rather than accuracy. Therefore, results from this test yield a high percentage of "false positives," literally "yes" answers when the correct answer is "no." Results generated by use of any screening test MUST be confirmed by use of more specific assay techniques. The Charm II test is neither designed for, nor capable of, serving as a definitive test, and some data have been reported without being confirmed by acceptable methods. FDA responded by conducting a larger study in which samples were collected in 14 cities across the U.S. FDA also utilized numerous and varied laboratory techniques to determine levels of illegal substances. FDA used the Charm II test and observed a high rate of violative residues. However, results of analyses using techniques specific for the compounds in question indicated no antibiotic or sulfamethazine residues. FDA concluded that "milk is safe and that consumers need not consider a change in their dairy product consumption." Relative Risk of Antibiotic Use Back to Table of Contents Although antibiotic use is highly regulated and compliance with regulations is outstanding, some have suggested that use of antibiotics in livestock production should cease altogether. Some have suggested that residues in milk are of particular concern to consumers who are allergic to certain drugs. Based on the FDA survey, it would appear that most consumers need not be concerned about suffering an allergic reaction to any potential drug residues in milk. However, FDA recommends that a physician be contacted by individuals who have been diagnosed as hypersensitive if they have doubts or concerns about possible exposure. The possibility of antibiotic residues inducing bacterial resistance in humans has been mentioned as a concern. Most bacterial resistance of medical importance is due to selection and transfer of resistance. Residue levels of a drug would have a negligible effect on the number of resistant bacteria. Although residues may be detectable, they will not have an effect on bacterial resistance. Even if resistance did occur in the cow, pasteurization of milk products would kill any resistant bacteria and preclude consumption by humans. Furthermore, potential residues in humans would be too low to result in selection for antibiotic resistant bacteria in humans. Summary Back to Table of Contents Drugs and chemicals have played a major role in reducing the cost and improving quality of milk, meat and poultry and will continue to do so. Because of the importance of a safe, wholesome food supply, consumers want to know more about the safety of typical livestock production practices. Products are not approved for animal use until safety for both animals and humans has been proven. Extensive regulations, enforced by federal and state agencies, result in extensive testing of the food supply and punishment of offenders. Ensuring a safe food supply in the future depends in large part on educational efforts to help producers, chemical manufacturers and feed manufacturers avoid practices that lead to illegal residue problems. Continued diligence on the part of government, researchers and especially food producers, will allow American consumers to continue to enjoy one of the most risk-free food supplies in the world. Suggested References Back to Table of Contents Baird, D. and I. F. Fraser. 1974. Blood production and ovarian secretion rates of estradiol 17B and estrone in women throughout the menstrual cycle. J. Clin. Endocrinol. 38:1009-1017. Burgat-Sacaze, V., P. Delatour and A. G. Rico. 1981. Bound residues of veterinary drugs. Ann. Rev. Vet. 13(3):277-289. Farber, T. M., M. Arcos and L. Crawford. 1983. Safety evaluation standards in the United States. In Anabolics in animal production: public health aspects, analytical methods and regulation, 509-514. Etienne Meissonnier Ed. Paris: Office International des Epizooties. Flood, C., J. H. Pratt and C. Longcope. 1976. The metabolic clearance and blood production rates of estriol in normal, non- pregnant women. J. Clin. Endocrinol. and Metab. 42:1-8. Henricks, D. M., S. L. Gray and J. L. B. Hoover. 1983. Residue levels of endogenous estrogens in beef tissues. In Anabolics in animal production: public health aspects, analytical methods and regulation, 233-248. Etienne Meissonnier Ed. Paris: Office International des Epizooties. National Research Council. 1985. Meat and poultry inspection—the scientific basis of the nation's program. National Academy Press, Washington, D. C. Pullen, M. 1990. Residues. Chapter 6 in Meat and health, advances in meat research, vol. 6, ed. A. M. Pearson and T. R. Dutson. New York: Elsevier Applied Science. Rico, A. G. and V. Burgat-Sacaze. 1983. New data in the metabolism of anabolic agents. In Anabolics in animal production: public health aspects, analytical methods and regulation, 263-272. Etienne Meissonnier Ed. Paris: Office International des Epizooties. Rubens, R. and A. Vermeulen. 1983. Estrogen production in man. In Anabolics in animal production: public health aspects, analytical methods and regulation, 249-262. Etienne Meissonnier Ed. Paris: Office International des Epizooties. Schafer, H. W. Food safety: a present and future issue. Extension Home Economics Newsletter, July 1987. Home Economics Program Area, Minnesota Extension Service, University of Minnesota, St. Paul. Senauer, Ben. 1989. Food safety: a growing concern. Staff Papers Series, 89-38. Dept of Agricultural and Applied Economics, University of Minnesota, St. Paul. Taylor, W. 1983. Risks associated with exposure of human subjects to endogenous and exogenous anabolic steroids. In Anabolics in animal production: public health aspects, analytical methods and regulation, 273-288. Etienne Meissonnier Ed. Paris: Office International des Epizooties. P. T. Anderson Extension Animal Scientist—Beef Cattle Department of Animal Science College of AgricultureB. A. Crooker Assistant Professor Department of Animal Science College of AgricultureM. M. Pullen Extension Meat Hygienist Clinical and Population Sciences Department College of Veterinary Medicine Community \ Environment \ Family \ Farm \ Garden \ Living Home \ Search \ Product Catalog \ News \ Workshops About Extension \ County Offices \ Partners Produced by Communication and Educational Technology Services, University of Minnesota Extension Service. In accordance with the Americans with Disabilities Act, this material is available in alternative formats upon request. Please contact your University of Minnesota county extension office or, outside of Minnesota, contact the Distribution Center at (612) 625-8173. 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