Selective intramammary antibiotic therapy during the nonlactating period in goats

Abstract

Forty-nine does were used to study the effectiveness of selective drying-off intramammary antibiotic therapy. All udder halves with intramammary infections by pathogens: coagulase negative staphylococci, Corynebacterium bovis, Streptococcus uberis or Pseudomonas sp., received a commercial dry-off treatment of cepharin benzathine labeled for the bovine. Noninfected halves were randomly treated. Dry period cures and new infections were determined by presence or absence of microbial cultures in milk samples aseptically collected at dry-off and at parturition. Antibiotic residues of penicillin activity in milk at parturition were determined by the Bacillus stearothermophilus var calidolactis disk assay. At dry-off, 43 of 97 (44.3%) udder halves had intramammary infections, 40 were coagulase negative staphylococcal infections, two were C. bovis and the other S. uberis. At parturition, 30 of 38 (78.9%) treated halves with intramammary infections at dry-off were cured, the eight not cured were coagulase negative staphylococcal infections. Five udder halves that were misclassified as noninfected at dry-off, but were coagulase negative staphylococcal infections and were not treated, were free of intramammary infections at parturition. New intramammary infections by coagulase negative staphylococci ( n=2) and Pseudomonas sp. ( n=1) affected less than 7% of the udder halves. Since the rate of new intramammary infections in all udder halves from both those receiving dry-off therapy and those not treated, was low, selective dry-off therapy could be considered. However, antibiotic residue was detected in milk from only one doe and the activity in milk from this doe was less than 0.016 IU penicillin/ml. Data also suggest intramammary cepharin benzathine therapy results in effective elimination of intramammary infections predominantly caused by coagulase-negative staphylococci at dry-off. Thus, no significant adverse effects of dry-off therapy as measured by new infections or presence of milk residues at parturition were found.