EFFECTS OF SELECTIVE DRY-COW THERAPY ON CULLING RATE, CLINICAL MASTITIS, MILK-YIELD AND COW SOMATIC-CELL COUNT - A RANDOMIZED CLINICAL FIELD-STUDY IN COWS

The effect of dry-cow therapy was evaluated on the basis of the cullin g rate, occurrence of clinical mastitis, mean of cow milk somatic cell counts (CMSCC), and milk yield, in a trial including 608 cows. The co ws were randomly divided into four groups: control soup A (92 cows), g roup B treated with placebo (base ointment of Benestermycin(R): (Leo) without antibiotics) (105 cows), one intramammary dose per infected qu arter; group C treated with Benestermycin(R) (Leo), one intramammary d ose being infused in each infected quarter (196 cows); and soup D trea ted with Leocillin(R) with dihydrostreptomycin (Leo); one intramammary dose being used every second day, on four occasions per infected quar ter (215 cows). The study included infected cows. If less than three o f the quarters of the udder were diagnosed as having mastitis at first sampling, only infected quarters were treated. Otherwise, all quarter s were treated. Multivariable analysis showed no significant effect of therapy on culling rate. The control groups (A + B) had a greater inc rease of cows having at least one case of clinical mastitis compared t o the therapy groups (C + D), (from 0.26 to 0.57 in controls comparing to 0.38 to 0.43 in therapy groups). The difference between control an d therapy groups during lactation was close to significant both before and after in the lactation after therapy (P < 0.10). The multivariabl e analysis showed a significant benefit of dry-cow therapy of 0.409 In unit in geometric mean CMSCC (corresponding to 125 000/ml), 200 000/m l in weighted CMSCC and 189 kg milk yield per lactation. According to these results selective dry-cow therapy for cows included in this stud y is recommended.