THE RESPONSE OF LACTATING COWS AND GROWING HEIFERS TO TREATMENT FOR PARASITES

Abstract

A series of three trials, two with lactating cows and one with growing heifers on pasture, utilized over 200 cows and heifers to establish whether there was a production response to the anthelmintic, "Tramisol" (levamisole phosphate). The lactating cows were subdivided into control and treated animals at parturition. Treated animals were injected with Tramisol on the day following parturition and 8 wk later. Heifers were treated when they were put out to pasture and every 4 wk thereafter. In the first trial with lactating cows there was no effect of treatment on milk yield or milk fat percent but body weight loss was less during the first 84 days for the treated versus control cows. In the second trial with lactating cows, milk yield was higher for total lactation and from 57 to 180 days for the treated cows. Body weight loss was also less during the first 50 days of lactation. There were no differences between the control or treated groups in either number of services required or days open. Heifers injected with Tramisol, when put on pasture, gained more body weight than control animals, particularly during periods of stress. Considering that the parasitic infestation in the herd was low the positive responses observed in these trials, although variable, warranted the conclusion that, in the majority of dairy herds in the area, routine anthelmintic treatment would be beneficial. Key words: Milk yield, growth, dairy cattle, anthelmintic treatment