USE OF PHYSIOLOGICAL VARIABLES TO PREDICT MILK-YIELD AFTER CLINICAL MASTITIS IN DAIRY-CATTLE

Objective-To determine the association between intramammary infections caused by various bacteria and hepatic damage, as measured by serum s orbitol dehydrogenase (SDH) activity, WBC counts, and PCV and the asso ciation of clinical variables with milk production after a case of cli nical mastitis. Design-Prospective, cohort study. Animals-82 cows with clinical mastitis. Procedure-Information on milk production, mastitis status, and selected physiologic variables was collected during a 1-y ear period. Milk samples for bacteriologic evaluation were collected o n day 1 of an episode of clinical mastitis. Physical examination was p erformed and blood samples for laboratory evaluation were collected on days 1, 5, and 9. Primary outcome was mature equivalent 305-day (ME30 5) milk production. Correlations were assessed using a multiple regres sion model. Results-Higher WBC counts were associated with higher ME30 5 values. For cows with coliform mastitis, increases in SDH values wer e associated with higher ME305 values. For cows with coliform and stre ptococci/staphylococci mastitis, PCV was associated with ME305 values. Higher PCV values were associated with lower ME305 values for strepto cocci/staphylococci and coliform infections. Clinical Implications-The association between milk production and WBC count indicated that cows mobilizing WBC were better able to neutralize mammary gland infection s, which may result in better milk production. The association between milk production and PCV suggested that maintaining hydration in cows with clinical mastitis may be a critical aspect of treating all cows w ith mastitis.