Performance-based targeted selective anthelmintic treatment regime for grazing dairy calves

Abstract

The possibility of utilising a performance-based targeted selective treatment (TST) anthelmintic regime in grazing dairy calves to reduce anthelmintic use while maintaining productivity was investigated on two commercial dairy farms in Canterbury, New Zealand. For five months, 107 14-week-old calves on Farm A and 100 10-week-old calves on Farm B were either treated with anthelmintic at monthly intervals or treated with anthelmintic in a performance-based TST regime based on their ability to meet monthly target growth rates. For TST animals, individual mean target liveweight gains were calculated for each month and animals that failed to reach their target live weight were treated with anthelmintic. Compared with their monthly treated counterparts, the number of anthelmintic treatments administered to TST animals was reduced by 84% and 65% for Farm A and Farm B, respectively. Although there was no difference between treatment groups in mean calf live weight (P >0.05), mean cumulative liveweight gain in TST animals was reduced by 6% (P <0.01) and 4% (P >0.05) compared with their monthly treated counterparts for Farm A and Farm B, respectively. Overall, the performance-based TST regime reduced anthelmintic usage with a small compromise in calf growth. It is anticipated that such regimes can provide an ethical and sustainable method of parasite control in grazing dairy calves.