Influence of an intramammary infusion at drying-off of combined penethamate hydriodide, benethamine penicillin, and framycetin sulfate on intramammary infections and somatic cell counts in dairy sheep.

The dynamics of intramammary infection (IMI) during the dry period were studied in 435 half-udders of 229 Assaf ewes, belonging to 2 flocks with high and medium IMI prevalences. Ewes were randomly assigned to 2 lots: 1) treated lot (TL) with 223 half-udders (118 ewes), which received complete dry therapy (1 syringe/teat) of an antibiotic combination containing 100 mg of penethamate hydriodide, 280 mg of benethamine penicillin, and 100 mg of framycetin sulfate, and 2) control lot (CL) with 212 nontreated half-udders (111 ewes). Two samplings per half-udder were carried out on 2 different days in the 5 d preceding drying-off, and 2 other samplings were again carried out in the 5 first d of the postpartum period. The length of the dry period averaged 109.0 d. Cure, persistent infections, reinfection, and new infection rates were 81.7, 12.8, 5.5, and 7.9%, respectively, for TL and 13.3, 70.4, 16.3, and 22.8%, respectively, for the CL. The prevalence of IMI decreased significantly from 48.9% at drying-off to 13.0% at lambing for the TL, but it did not vary for the CL (46.2 and 52.4%, respectively). Within the TL, IMI prevalence significantly diminished for Staphylococcus (41.3 to 9.9%) and Streptococcus (5.8 to 1.8%) genera, and more specifically this decrease was most evident for Staphylococcus epidermidis and Streptococcus agalactiae species. Log somatic cell count (SCC) diminished significantly between drying-off (5.68) and lambing (5.33) in the TL, whereas log SCC did not vary in the CL (5.61 vs. 5.66). This SCC reduction was very significant in the flock with the greater IMI prevalence. As a conclusion, the antibiotic formulation used as dry therapy drastically diminished IMI prevalence and SCC during the dry period in dairy ewes as a result of greater IMI cure rates and lower reinfection and new infection rates in the TL compared with the CL.