Effect of milk production system on the enzootic stability to Anaplasma marginale and Babesia bovis in calves in the Campo das Vertentes region of Minas Gerais state, Brazil

Abstract

We conducted a cross-sectional observational study, in order to determine the frequency of anti-A. marginale and anti-B. bovis antibodies in calves from four to 12 months of age from ten farms that producing B type milk and an equal number that produce raw milk refrigerated, located in the Campo das Vertentes region of Minas Gerais state, in the period September 2008 to August 2009. Blood smears were performed, serologic testing by indirect immunofluorescence technique (IFAT), given the packed cell volume, rickettsemia, and the clinical scores of animals infected by A. marginale. In the farms that produce B type milk, the overall average frequency of seropositive calves was 94.47% (166/176) and 89.20% (157/176) for A. marginale and B. bovis, respectively. Already on the farms that produce raw milk refrigerated, the overall average frequency of A. marginale was 92.59% (149/161) and for B. bovis from 86.30% (139/161), and there was no significant difference (p > 0.05) in the frequency of calves infected for both hemoparasitic between the two systems of milk production. Statistically significant (p < 0.05) levels of rickettsemia among calves from farms with different types of milk production, where calves from properties that produce B type milk had a higher percentage of erythrocytes infected with A. marginale. In this study there was a predominance of calves with clinical score 1 (subclinical infection by A. marginale), with the overall average frequency equal (p > 0.05) among calves from properties that produce B type milk and raw milk refrigerated. The results of this study indicate that, in the Campos das Vertentes region of Minas Gerais, the production system does not interfere with the enzootic stability for A. marginale and B. bovis in calves from dairy farms B milk or raw milk refrigerated, with low probability of anaplasmosis and/or babesiosis in adults animals.