THE EFFICACY OF MICHELS DOSE AND MOVE SYSTEM ON GASTROINTESTINAL NEMATODE INFECTIONS IN DAIRY CALVES

The efficacy of a move to aftermath in July combined with moxidectin o r fenbendazole treatment for the control of parasitic gastroenteritis (PGE) in calves was evaluated in three field experiments in the Nether lands. In all five treated groups high gastrointestinal nematode infec tions and PGE were prevented by a dose and move in July. Cooperia infe ctions increased to moderate levels in two groups treated with moxidec tin and one group treated with fenbendazole. In both other groups and also for Ostertagia in these three groups, low to extremely low infect ions were acquired. In the first experiment high primary infections, r esulting in high faecal egg counts and a moderate increase of blood pe psinogen values occurred before the dose and move. Nevertheless, these primary infections were not high enough to result in PGE. In both oth er experiments primary infection levels were low and faecal egg counts increased to 100-650 eggs/g faeces at the end of grazing season. The blood pepsinogen values of non-treated control groups demonstrated tha t it took more than a month after their move to aftermath before subst antial reinfection occurred on the new pasture. In the first and the l ast experiment only, high Ostertagia and Cooperia infections developed in the control group at the end of the grazing season, though it did not result in clinical PGE. The experiments demonstrate all theoretica l risks of the dose and move system: (1) PGE early in the grazing seas on as a result of high overwintered pasture infectivity. (2) PGE just before the move as a result of an early midsummer increase in pasture infectivity. (3) PGE around housing as a result of insufficient suppre ssion of pasture infectivity late in the grazing season. (4) Underexpo sure to nematode infections due to a high suppression of nematode infe ctions. Nevertheless, it can be concluded that under normal conditions the dose and move system remains to be a valuable and easily applicab le system for the control of PGE. (C) 1998 Elsevier Science B.V.