Residues of zeta-cypermethrin in bovine tissues and milk following pour-onand spray application

The depletion of zeta-cypermethrin residues in bovine tissues and milk was studied. Beef cattle were treated three times at 3-week intervals with 1 ml 10 kg(-1) body weight of a 25 g litre(-1) or 50 g litre(-1) pour-on formul ation (2.5 and 5.0 mg zeta-cypermethrin kg(-1) body weight) or 100 mg kg(-1 ) spray to simulate a likely worst-case treatment regime. Friesian and Jers ey dairy cows were treated once with 2.5 mg zeta-cypermethrin kg(-1) in a p our-on formulation. Muscle, liver and kidney residue concentrations were ge nerally less than the limit of detection (LOD = 0.01 mg kg(-1)). Residues i n renal-fat and back-fat samples from animals treated with 2.5 mg kg(-1) al l exceeded the limit of quantitation (LOQ = 0.05 mg kg(-1)), peaking at 10 days after treatment. Only two of five kidney fat samples were above the LO Q after 34 days, but none of the back-fat samples exceeded the LOQ at 28 da ys after treatment. Following spray treatments, fat residues were detectabl e in some animals but were below the LOQ at all sampling intervals. Zeta-cy permethrin was quantifiable (LOQ = 0.01 mg kg(-1)) in only one whole-milk s ample from the Friesian cows (0.015 mg kg(-1), 2 days after treatment). In whole milk from Jersey cows, the mean concentration of zeta-cypermethrin pe aked 1 day after treatment, at 0.015 mg kg(-1), and the highest individual sample concentration was 0.025 mg kg(-1) at 3 days after treatment. Residue s in milk were not quantifiable beginning 4 days after treatment. The mean concentrations of zeta-cypermethrin in milk fat from Friesian and Jersey co ws peaked two days after treatment at 0.197 mg kg(-1) and 0.377 mg kg(-1), respectively, and the highest individual sample concentrations were 2 days after treatment at 0.47 mg kg(-1) and 0.98 mg kg(-1), respectively. (C) 200 1 Society of Chemical Industry.