Abstract
An ear-tag made of synthetic resin containing 15%(w/w) permethrin was attached to each ear of 416 dairy cattle which were put out to pastures of three ranches, D, H, and K, in Tochigi Prefecture. The tags remained attached for about six months from April to October, 1988. The tags were collected from some of the cattle once or twice monthly during the period and weighed. Quantity of permethrin remaining in tags was also determined. The results obtained are summarized as follows:
1. Weight of the ear-tag and content of permethrin in the tags steadily decreased at a high rate during the first four months, thereafter the decreasing rate became lower. Loss of permethrin in the tags was about 900 mg (the daily mean, 5.5 mg) during the whole testing period.
2. The quantity of permethrin loss per tag per day was calculated to be 8.925 mg the first month, 4.065 mg the fourth month and 0.825 mg the sixth month by the regression analysis.
