The study objective was to compare the efficacy of 3 commercial dry cow mastitis formulations regarding quarter-level prevalence of intramammary infections (IMI) postcalving, cure of preexisting infections over the dry period, prevention of new infections during the dry period, and risk for a clinical mastitis case between calving and 100. d in milk (DIM). A total of 1,091 cows (4,364 quarters) from 6 commercial dairy herds in 4 different states (California, Iowa, Minnesota, and Wisconsin) were enrolled and randomized to 1 of the 3 treatments at dry-off: Quartermaster (QT; 1,000,000 IU of procaine penicillin G and 1 g of dihydrostreptomycin; Pfizer Animal Health, New York, NY), Spectramast DC (SP; 500 mg of ceftiofur hydrochloride; Pfizer Animal Health), or ToMorrow Dry Cow (TM; 300. mg of cephapirin benzathine; Boehringer Ingelheim Vetmedica Inc., St. Joseph, MO). Quarter milk samples were collected for routine bacteriological culture before dry cow therapy treatment at dry-off, 0 to 6 DIM, and 7 to 13 DIM and an on-farm record-keeping system was used to retrieve data on clinical mastitis cases. Noninferiority analysis was used to evaluate the effect of treatment on the primary outcome, risk for a bacteriological cure during the dry period. Multivariable logistic regression techniques were used to describe the effect of treatment on risk for presence of IMI postcalving and risk of a new IMI during the dry period. Cox proportional hazards regression was used to describe the effect of treatment on the risk and time for quarters to experience an episode of clinical mastitis between calving and 100 DIM. The overall crude quarter-level prevalence of infection at dry-off was 19.2%. The most common pathogen isolated from milk samples at dry-off was coagulase-negative Staphylococcus, followed by Aerococcus spp. and other Streptococcus spp. Noninferiority analysis showed no effect of treatment on risk for a cure between dry-off and calving [least squares means (LSM): QT = 93.3%, SP = 92.6%, and TM = 94.0%] and secondary analysis showed no effect of treatment on risk for presence of an IMI at 0 to 6 DIM (LSM: QT = 16.5%, SP = 14.1%, and TM = 16.0%), risk for development of a new IMI between dry-off and 0 to 6 DIM (LSM: QT = 14.8%, SP = 12.3%, and TM = 14.2%), or risk of experiencing a clinical mastitis event between calving and 100 DIM (LSM: QT = 5.3%, SP = 3.8%, and TM = 4.1%). In conclusion, no difference was observed in efficacy among the 3 products evaluated when assessing the aforementioned quarter-level outcomes.
Bibliographical noteFunding Information:
Financial support for this study was provided by Boehringer Ingelheim Vetmedica Inc. (St. Joseph, MO) and the College of Veterinary Medicine from the University of Minnesota (St. Paul). The authors acknowledge the collaborators from Iowa State University and University of California, Davis, as well as the Laboratory for Udder Health (Minnesota Veterinary Diagnostic Laboratory, University of Minnesota, St. Paul), the Veterinary Diagnostic Laboratory (Iowa State University, Ames), and the Milk Quality Laboratory at the Veterinary Medicine Teaching and Research Center (University of California, Davis, Tulare, CA), whose participation was essential for the conduction of this study. Finally, we thank the participating farm owners and staff, as well as the study technicians.
- Dry cow mastitis
- Dry cow therapy
- Quarter-level outcome