Residues of famphur in bovine tissues and milk following its application as a pour-on insecticide

Abstract

Three experiments were conducted to determine residues of famphur in tissues and milk of cattle following its topical application. Subcutaneous fat, sampled by biopsy, from animals treated at 150 mg famphur per kg body weight contained maximum residues of famphur (about 10 mg kg-1, average) one day after treatment. Levels of treatment at 50 mg kg-1 and 25 mg kg-1 yielded similar but lower residues after the same period (2.08 and 1.8 p.p.m, respectively). The half-life of famphur residues was independent of the initial residue levels and was calculated as 0.9 day. Mean residues were negligible (highest mean 0.08 p.p.m.) by five days after treatment. Post-mortem sampling of cattle treated with famphur at 45 mg kg-1 showed that at one day and seven days after treatment, residues in fats (up to 1.25 p.p.m. and 0.53 p.p.m. respectively) and muscle (1.41 p.p.m. and 0.71 p.p.m. respectively) were similar but were higher than the negligible levels (0.05 p.p.m. or less) found in liver and kidney. By 14 days, levels in all tissues were very low (0.11 p.p.m. or less). In milk from cows treated with 23 mg famphur kg-1, 76 per cent of the famphur was found in the butterfat and a maximum level (0.237 p.p.m.) in whole milk was found in the first milking after treatment. Residues were negligible (0.008 p.p.m.) by the third day.