Field trials in sheep with the anthelmintic thiophanate.

Productivity and tolerance trials were conducted with the anthelmintic thiophanate (Nemafax; May & Baker) in sheep in the United Kingdom. Tolerance studies, conducted in sheep of various types under several management systems, in which thiophanate was given orally at recommended dosage (50 to 100 mg/kg), or multiples thereof, in single or repeated doses showed that treatment was in all cases well tolerated. Thiophanate administered at 75 mg per kg or 250 mg per kg to groups of growing lambs with low faecal egg counts produced no post treatment depression of weight gain. When breeding ewes were treated with thiophanate at 150 mg per kg on days 14, 21 and 28 after introduction of rams to the flock, the anthelmintic produced no adverse effect on lambing performance. Trials to assess the beneficial effects of treatment were conducted in weaned lambs naturally infected with gastrointestinal nematodes. Groups of lambs were treated monthly with either thiophanate or tetramisole at recommended dosages. The two anthelmintics produced similar weight gains in the lambs and these were significantly better than those of untreated controls. In untreated controls faecal egg counts increased markedly and the clinical condition of these animals deteriorated.