Residues of dioxathion in adipose tissue of cattle subjected to multiple dippings

Abstract

Two experiments were conducted at the Cattle Tick Research Station, Wollongbar, to ascertain the accumulation and degradation of residues in the adipose tissue of beef cattle after exposure to the acaricide, dioxathion. In the first experiment, six beasts were given an abnormally high exposure (three dippings in 0.075 per cent dioxathion within two hours) and subcutaneous fat samples were collected on the 1st, 2nd, 3rd, 4th, 8th and 11t h day after treatment. In the second experiment, 40 beasts were dipped three times at five day intervals in this acaricide as if to completely cleanse them of cattle tick, Boophilus microplus. Four beasts were sampled before and after slaughter on the 1st, 2nd, 3rd, 4th, 5th, 8th, loth, 12th, 16th and 32nd day after the last dipping. The following conclusions were reached : 1. Maximum residues of dioxathion in adipose tissue occur two to four days after treatment. 2. The half life for the disappearance of residues, once maximum levels were reached, was 16 days, and this was similar to that of some other commonly used organophosphorus acaricides (eg. ethion, chlorpyrifos) 3. Biopsy of the subcutaneous fat from the gluteal region was an acceptably reliable method for estimating residue levels in the fat depots of a beast. It is recommended that cattle subjected to three dippings at five day intervals in dioxathion be withheld from slaughter for a period of at least six weeks to allow residues to fall below the Australian maximum residue limit of 1 mg kg-1.