Pesticide Residues in Animal Products
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143 Pesticide Residues in Animal Products ROSCOE H. CARTER, H. V. CLABORN, G. T. WOODARD, AND RAY E. ELY ANIMAL products intended for food cide chemical" means any substance may become contaminated with pesti- which alone, in chemical combination, cide chemicals in a number of ways. or in formulation with one or more DDT and other chlorinated mate- other substances is an economic poison rials are used to control insects on such within the meaning of the Federal forage crops as alfalfa, clover, and Insecticide, Fungicide, and Rodenti- grass and on peas, beans, corn, and cide Act. Raw agricultural commodi- similar crops, of which a part is used ties include fresh fruits and vegetables, as animal feed. Some pest killers, used grains, nuts, eggs, raw milk, meats, and at recommended dosages and in ac- similar agricultural produce. It docs cordance with good agricultural prac- not include foods that have been proc- tices, leave enough residue on forage essed, fabricated, or manufactured by crops so that some is stored in the cooking, freezing, dehydrating, or mill- animal or excreted in milk if the forage ing. is fed to livestock. Pastures or grain Detecting and estimating pesticide that have had pesticide treatments residues in the biological materials by also may be a source of contamination chemical analysis are complicated pro- of animal products. cedures. General methods, such as the DDT—the common name for the determination of the organic chlorine commercial product dichloro-diphenyl- content, are used sometimes to deter- trichloroethane—has been found in mine residues. Specific and spectro- milk samples from cows stabled in photometric methods are available for barns sprayed with it, even though the certain pesticide chemicals. cows were outside when the spraying The procedures generally require an was done. Enough DDT was picked extraction of the biological product up from feed troughs, water fountains, with an organic solvent, such as Skelly- and other sources to cause excretion in solve B or benzene. These extracts con- the milk. Some other pesticides, sprayed tain fat, glycerides, and other constitu- directly on the animals, have been ex- ents. Because some pesticide materials creted in the milk. are stable toward acids and some are Some of the pesticides used in spray- stable toward alkali treatments, pro- ing and dipping cattle, sheep, goats, cedures using those reagents have been and swine are stored in the animals' developed to break up the glycerides bodies. Some materials have caused without decomposition of the pesticide. serious disturbances and even fatali- Chromatographie procedures have also ties. Others have little apparent effect. been developed to aid in the separation Most of the pesticides used for insect of the pesticide residue from fats, waxes, control are soluble in the fat and are coloring matter, and such materials. stored in the fatty tissues of the animal. Methods of analysis capable of de- Three to four months are required tecting minute amounts have been de- before some of the chemicals are en- veloped so that it is possible to deter- tirely eliminated. mine residues considerably less than Public Law 518 provides for the o. I part per million (p. p. m.) for some establishment of tolerances for pesti- pesticides. cide chemicals in or on raw agricul- Bioassay procedures capable of de- tural commodities. The term ''pesti- termining residues less than o. i p.p.m. 144 Yearbook of Agriculture 1956 of some materials have also been de- with 2.4 pounds of DDT on an acre veloped. They are useful in detecting resulted in milk production containing toxic residues of metabolic products a maximum of lo.i p. p. m. of DDT; that are not detectable by the specific 0.6 pounds of DDT resulted in o.g method for the original toxicant. p. p. m. of DDT in the milk. A comparative study of the effects EXPERIMENTS in which dairy cows of dosage level and various methods of were fed forage that had been treated administration on the concentration with insecticides during the growing of DDT in milk indicated that in- season and other tests in which the cows creasing intakes of DDT as a residue were given oil solutions of the insecti- on hay or in oil solution gave progres- cides in capsules are briefly described. sive increases in the DDT concentra- The insecticides included DDT, BHG tion in the milk in a straight-line (the common name for the technical relation. This straight line had a great- product benzene hexachloridc), lin- er slope for intake as residue over dane, methoxychlor, chlordane, toxa- intake in oil solution. phane, aldrin, dieldrin, heptachlor, and DDT in oil solution and alfalfa con- endrin. taining various amounts of DDT resi- Growing alfalfa was sprayed with the due was fed to dairy calves. DDT in- insecticides at dosages recommended take varied from 0.07 to 2.9 milligrams for insect control. After an interval of 3 per kilogram of body weight, or 2.2 to to 10 days the crop was cut, field cured, 106 p. p. m. of the dry matter con- baled, and stored in barns 6 to 8 sumed. The storage of DDT in the months until used as feed. Normal, body and kidney fat ranged from 2 to healthy milking cows, generally four to 345 P- P- ^-5 ^^^ t^G concentration each test, were fed the hay with a sup- was proportional to the DDT intake. plemental grain ration. The amounts Residues of methoxychlor on alfalfa consumed daily and the milk produc- ranging from 16 to 109 p. p. m, did tion were recorded. not result in detectable amounts in the The tests were generally continued milk. Crystalline methoxychlor admin- 40 to 90 days, or until it was thought istered orally as a lo-percent solution that equilibrium had been established in soybean oil in daily dosages equiva- between intake and excretion of the lent to 2,000 p. p. m. of the feed con- insecticide. After this phase, the cows sumed, or approximately 19 mg. per were given oil solutions of the insecti- kg. of body weight, resulted in detect- cides in capsules at varying levels of in- able amounts of methoxychlor in the take considerably above the levels of milk. intake as residue. Milk samples were Four cows were fed hay containing taken every tenth day for chemical approximately 0.4 p. p. m. of lindane analysis. Since the chlorinated insecti- for 100 days and four cows received hay cides are fat-soluble and are present containing approximately 2.6 p. p. m. only in the butterfat portion of milk, of lindane for 60 days. The concen- butterfat determinations were made on trations of lindane in the milk of these all samples and the results calculated cows ranged from 0.13 to 0.27 p. p. m. and adjusted to a uniform butterfat Two lots of alfalfa hay, which had (FGM) content of 4 percent. Compos- been treated with toxaphene emulsion ite samples of the hay representing every at the rate of i .5 pounds per acre, were 10 days of feeding were analyzed for fed to two sets of three cows each for residue. Milk samples were collected in 150 and 100 days. The average insecti- most instances for some time after in- cide residue on the two lots of hay was secticide intake had been discontinued 81.8 and 31.8 p. p. m., equivalent to to obtain information on the persist- an average daily intake of 1.4 mg. and ence of the materials in the animals. 0.5 mg. per kg. of body weight, re- Alfalfa hay that had been treated spectively. The average toxaphene con- Pesticide Residues in Animal Products 145 tent of the milk from the two sets of when feeding the hay sprayed with 3.8 cows was 0.5 and o. i p. p. m., respec- ounces per acre; from o. 10 to 0.13 mg. tively. Increased dosages of toxaphene per kg. of body weight from the 8- in soybean oil solution resulted in ounce treatment. After the hay feeding increased excretion in the milk. tests, the cows were given increased Two lots of alfalfa hay, which had dosages of heptachlor in a soybean oil been treated with chlordane emulsion solution. No heptachlor was detected at the rates of i and 2 pounds per acre, in the milk of the cows fed the treated were fed to two sets of three cows each hay or given the oil solutions. for 150 and 100 days, respectively. The A metabolic product, heptachlore- average chlordane residue on the two poxide, was detected in the milk from lots of hay was 20.4 and 20.8 p. p. m., cow^s receiving heptachlor at dosages equivalent to an average daily intake of more than i .3 mg. per kg. of body of 0.39 and 0.37 mg. per kg. of body weight. weight, respectively. The average chlor- Two lots of alfalfa hay, w^hich had dane content of the milk from the two been treated with 2.7 ounces and 6.6 sets of cows was 0.2 and o p. p. m., ounces of endrin per acre, were fed to respectively. Increased dosages of chlor- two sets of four cows each for 48 and dane in soybean oil solution resulted in 44 days, respectively. The average increased excretion in the milk. endrin content of the milk was ap- Alfalfa hay that had been sprayed proximately o.i p. p. m.—which is with aldrin at the rate of 3.9 ounces below the sensitivity of the method of per acre was fed to four milk cows for analysis.