THE PROPHYLACTIC EFFECT OF A TEAT SEALER ON BOVINE MASTITIS DURING THE DRY PERIOD AND THE FOLLOWING LACTATION

Aim, To determine the prophylactic efficacy of a teat sealer, administ ered at drying off, in reducing new intramammary infections in the dry period and the following lactation. Methods. A total of 528 cows with late lactation somatic cell counts < 200 000 cells/ml was identified in three commercial herds. Of these, bacteriological examination showe d 482 cows were uninfected in all four quarters and 46 were infected i n only one quarter. At drying off, uninfected quarters were randomly a llocated to the following treatments: no infusion (negative controls), infusion with a bismuth subnitrate based teat sealer, infusion with t eat sealer + antibiotic, or infusion with a cephalonium-based dry cow antibiotic (positive control). New infections were identified during t he dry period by periodic udder palpations and at calving by bacteriol ogical culture. Results, All three infused treatments reduced the inci dence of new intramammary infections due to Streptococcus uberis, both during the dry period and at calving, by about 90% (p < 0.01). The ma jority of the infections were due to Streptococcus uberis. For al trea tments, a 50% lower incidence of clinical mastitis over the first 5 mo nths of the ensuing lactation was reported by farmers. X-ray imaging o f 19 teats showed that the tear sealer material was retained, at least in part, in the lower teat sinus over about 100 days of the dry perio d.Conclusions. Closure of the tear canal from day one of the dry perio d as achieved by the teat sealer was as effective in reducing new dry period infections as the infusion of a long-acting dry cow antibiotic formulation. The lower incidence of new infections in the ensuing lact ation among the infused quarters implies that fewer subclinical infect ions persisted from the dry period. Use of teat sealers at drying off appears to offer the same prophylactic efficacy as the dry cow antibio tic approach.