Aldrin, heptachlor and beta -hexachlorocyclohexane to dairy cows at three oral dosages. 1. Residues in milk and body fat of cows early and late in lactation.

Abstract

1. To investigate the transfer of aldrin, heptachlor and beta -hexachlorocylohexane ( beta -HCH) from feed to milk and body fat of dairy cows, 9 cows early and 9 cows late in lactation were assigned to groups of 3 and given different daily dosages of a mixture of pesticides: 1 mg, 2 mg or 4 mg each of aldrin, heptachlor and beta -HCH/cow daily for 4 weeks. Milk fat and body fat samples were analysed for pesticide content. Aldrin and heptachlor could not be detected in milk fat or in body fat. Average contents of beta -heptachlorepoxide were below 0.1 mg/kg even for the highest dosage. The beta -HCH and dieldrin contents in milk fat increased rapidly. The ratio of contents between the groups roughly corresponded to that between the dosages. The cows early in lactation did not have less beta -HCH and dieldrin than the cows late in lactation. During the first 14 days after withdrawal the contents of beta -HCH and dieldrin usually decreased by more than half. The average transfer coefficients for cows late in lactation were all below 10% and for cows early in lactation about 3 times as high, because yield of milk fat was nearly 3 times as high early in lactation. The pesticide contents in body fat too increased but did not reach the same level as in milk fat. Cows early in lactation usually had higher contents in body fat than cows late in lactation. An estimate of the average relative mass of beta -HCH and dieldrin in milk fat and body fat is given. (Abstract retrieved from CAB Abstracts by CABI’s permission)