ESTIMATION OF MILK-PRODUCTION LOSSES DUE TO SUBCLINICAL MASTITIS IN DAIRY-CATTLE IN COSTA-RICA

Five dairy farms, situated on the slopes of the volcano Poas in the pr e-mountain cloud forest ecological zone, Alajuela and Heredia Province s, Costa Pica, provided data for estimation of the production losses d ue to sub-clinical mastitis. Within the same farm, cows with proven su b-clinical mastitis were marched with cows without signs of sub-clinic al mastitis, according to breed, lactation number and days in lactatio n. A total of 529 cows were detected with sub-clinical mastitis, of wh ich only 200 could be paired with control cows free of mastitis; each pair was used only once. Crude milk production losses per cow with sub -clinical mastitis were estimated at 1.56 kg day-1 for daily milk yiel d. Milk production loss per affected quarter due to sub-clinical masti tis was estimated to be 17.6% on average. The decrease in milk product ion in heifers with sub-clinical mastitis did not differ significantly from the decrease in production in older cows. No significant differe nce in milk production loss was detected when the data were stratified on parity or the number of quarters affected.