Introduction:

The knowledge of the variables associated with the prevalence of clinical mastitis (PCM) can help to design more efficient control measures. Objectives: To quantify PCM in a specialized dairy herd, according to the influence ofbirth order (BO) and the effect of racial component (RC).

Materials and methods:

A transversal study was carried out to calculate PCM according to BO (1, 2, 3, 4, 5, and 6, or more), conditional probability (CP), PCM for each RC, and PCM according to BO for each RC. The x2 test was performed.

Results:

An overall PCM of 15% was observed. A directly proportional relationship was established between BO and PCM. The calculated prevalences were 9.9, 10.9, 12.2, 21.6, 21.7, and 21.4% for BO 1, 2, 3, 4, 5, and 6 or more, respectively, with significant statistical differences. CP varied between 9% (BO 1 and 2) and 22.8% (BO 3 and 4). A PCM of 16.7% was observed for Holstein (H) cows, 8.9% for Holstein F1 with Blanco Orejinegro cows (BON), and 9.4% for % H x V BON, with no significant differences. However, when comparing H with BON crosses, regardless of the percentage of the BON racial components, significant statistical differences were observed.

Conclusions:

PCM increases with increased BO; therefore, disease surveillance programs should be intensified in older cows. The BON breed contributes a rusticity factor to its crosses that decreases PCM.

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