randomized equivalence study evaluating the efficacy of two commercially available teat sealants in dairy cows

Use of internal teat sealants is common in the U.S. to prevent new intramammary infections during the dry period. The objective of this study was to compare the efficacy of a new internal teat sealant containing bismuth subnitrate (SOa) to the first product introduced to the U.S. dairy industry (ORBb). The hypothesis was completed using a multi-site randomized, positively controlled equivalence evaluation of new intramammary infection risk difference over the dry period. At dry-off, milk samples were collected for culture and then cloxacillin benzathinec was administered, followed by the randomly assigned internal teat sealant (SO = 404 cows; ORB = 418 cows). After calving, repeat milk samples were collected. The effect of treatment on quarter-level new intramammary infection risk, cured intramammary infection risk, and risk of presence of intramammary infection post-calving was determined using generalized linear mixed models. The effects of treatment on cow-level outcomes, including incidence of clinical mastitis, culling and death, and performance in early lactation based on test-day milk production and somatic cell count, were also evaluated. The dry period new intramammary infection adjusted risk difference (SO minus ORB) was -1.60% (95% CI -5.62, 2.42). Final models demonstrated that there was no difference in risk rates of quarter-level outcomes between treatment groups. Analysis of cow-level factors, including clinical mastitis, culling and death rate within the first 120 DIM, also revealed no differences. Results of this study indicate that SO was equivalent to ORB for dry period new intramammary infection risk when utilizing blanket dry cow therapy.