Prophylaxis of trichostrongylid infection afforded by low-dose phenothiazine given in two successive years to first-season calves on a common area of pasture.
Reduced trichostrongylid infection on herbage and in calves was obtained when first-season calves, grazing a common area of pasture, received low-dosage phenothiazine (PTZ) in two successive years. The average daily dose of PTZ was 7.0 or 10.3 mg kg-1 in the first year and, in the second, between 5.0 and 7.0 mg kg-1. The effect on herbage infection was attributed mainly to ovicidal action. Treatment increased weight gain by 22 and 50 to 60 per cent in the respective seasons. The results suggested a cumulative effect produced by treating calves of successive years. Two calves developed PTZ-induced photosensitivity (corneal opacity) in the first season, and two calves in the second season but in the latter, severe bronchopneumonia was believed to be a predisposing factor. To avoid photosensitivity and still maintain adequate drug activity, the daily intake of PTZ should probably be restricted to around 6 mg kg-1.
Agricultural Institute, Grange/Dunsinea Research Centre, Castleknock, Dublin, Ireland.
C J
CJ
Somers
N E
NE
Downey
J
J
O'Shea
D000284:Administration, Oral; D000818:Animals; D001835:Body Weight; D002417:Cattle; D002418:Cattle Diseases / Q000469:parasitology* / Q000517:prevention & control; D005243:Feces / Q000469:parasitology; D010640:Phenothiazines / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D010787:Photosensitivity Disorders / Q000139:chemically induced / Q000662:veterinary; D014252:Trichostrongyloidiasis / Q000662:veterinary*; D014253:Trichostrongylosis / Q000517:prevention & control / Q000662:veterinary*
D010640:Phenothiazines; C031637:phenothiazine