Studies on the anthelmintic effect of a sustained release pre-grazing treatment with morantel in grazing cattle in Sweden.

The effect of a morantel sustained release bolus (MSRB) to control gastrointestinal parasitism in cattle grazing their first season was assessed under field conditions in Sweden. The MSRB was administered orally to calves immediately prior to turnout onto spring pastures in May 1978. The level of pasture contamination of infective larvae was decreased by 73 per cent in August and by 98 per cent in September. There was a 72 per cent reduction in worm burdens acquired over the entire grazing season. During the same period the mean improvement in weight gain was 21.5 kg per animal. Weight gains were also recorded during housing until slaughter in April 1979, i.e. 335 days after MRSB administration at which time the treated animals were on an average 17.1 kg heavier than controls.