COMPARISON OF RESISTANCE TO THEILERIA-SERGENTI INFECTION BETWEEN HOLSTEIN AND JAPANESE-BLACK CATTLE UNDER CRAZING CONDITIONS

To analyze the resistance against Theileria sergenti infection in Hols tein and Japanese Black cattle under field conditions, clinical, hemat ological and parasitological findings in these breeds of cattle that w ere grazed in the same pasture were examined during the grazing period . Holstein cattle showed a higher level of parasitemia than Japanese B lack. With the progression of parasitemia, packed cell volume (PCV) de creased in both breeds and the minimum value of PCV recorded in Japane se Black was higher than in Holstein. The daily gain rate was higher f or Japanese Black cattle than Holstein. These results suggest that the Japanese Black cattle display a higher resistance to T. sergenti infe ction than the Holstein under field conditions, based on a previous in fection test carried out under experimental conditions without externa l factors.