TUBERCULOSIS IN DAIRY CALVES - RISK OF MYCOBACTERIUM SPP EXPOSURE ASSOCIATED WITH MANAGEMENT OF COLOSTRUM AND MILK

A prospective study was undertaken to investigate the association betw een the risk of Mycobacterium spp. exposure and management of colostru m and milk in two groups of Holstein calves in a Mycobacterium bovis i nfected commercial dairy herd in Mexico. Group 1 (high risk) included 91 calves fed with pooled colostrum from several cows in the study her d and raw milk from the bulk tank. Group 2 (low risk) was composed of 279 calves fed with colostrum from tuberculin skin-test negative cows and powdered milk. At 6 months of age, calves in Groups 1 and 2 were s kin-tested for detection of Mycobacterium spp. exposure. In the high r isk group, 25 (27%) of 91 calves tested positive to the caudal fold sk in-test; in the low risk group, 43 (15%) of 279 calves were also class ified as positive. After controlling for the confounding effect of ski n-test reactor status of darns, it was found that the risk of Mycobact erium spp. exposure was associated with management of colostrum and mi lk. The adjusted odds for Mycobacterium spp. exposure were 1.9 times h igher in the high risk group when compared with the low risk group(P = 0.05). Further, the risk of skin-test reactors increased from 11% in calves born from skin-test negative cows (in the low risk group) to 33 % in calves born from skin-test positive cows (in the high risk group) .