Randomized equivalence study comparing the efficacy of 2 commercial internal teat sealants in dairy cows

摘要

The use of an internal teat sealant (ITS) at dry-offhas been repeatedly shown to improve udder healthin the subsequent lactation. However, almost all ITSresearch conducted in North America has evaluatedone product (Orbeseal, Zoetis, Parsippany, NJ). Theobjective of this study was to evaluate a new ITS product(Lockout, Boehringer-Ingelheim Animal Health,Duluth, GA), by comparing it directly to Orbeseal ina multi-site, randomized, positively controlled equivalencetrial for health indicators during the dry period[quarter-level new intramammary infection (IMI) risk,IMI cure risk, and IMI risk at 1 to 13 d in milk, DIM]and during the first 100 DIM [clinical mastitis and cullingor death risk and test-day milk somatic cell count(SCC) and milk yield]. At dry-off, cows were randomlyallocated to be treated with Orbeseal or Lockout afterblanket administration of a cloxacillin dry cow therapyproduct. Cows were then followed from dry-off until100 DIM. Intramammary infection status at enrollmentand at 1 to 13 DIM was determined using standardbacteriological methods, allowing for the measurementof IMI dynamics during the dry period (i.e., IMI curesand new IMI). The effect of ITS group on dry periodIMI cure, dry period new IMI, and IMI risk at 1 to13 DIM was determined using generalized linear mixedmodels (logistic). Marginal standardization was used toderive risk difference estimates. An equivalence hypothesistest was conducted to compare ITS groups for dryperiod new IMI risk (margin of equivalence was ±5%units). The effect of ITS group on clinical mastitis andculling or death was determined using Cox proportionalhazards regression. The effect of ITS group on testdaySCC and milk yield was determined using linearmixed models. Final models indicated that measures ofquarter-level IMI dynamics were similar between ITSgroups (i.e., risk difference estimates and 95% confidenceintervals all close to zero). Furthermore, Lockoutwas found to be equivalent to Orbeseal for dry periodnew IMI risk using an equivalence hypothesis test.Hazard ratio estimates for clinical mastitis and cullingor death were close to 1 and differences in SCC andmilk yield between ITS groups were close to 0, indicatingnegligible effects of ITS group on test-day SCCand milk yield. In most cases, these effect estimateswere relatively precise (i.e., narrow 95% confidenceintervals). We conclude that producers using blanketdry cow therapy could consider including Orbeseal orLockout treatment in their programs.