The objective of this study was to compare culture- and algorithm-guided selective dry-cow therapy (SDCT) programs with blanket dry-cow therapy (BDCT) in a multi-site, randomized, natural exposure clinical trial for the following cow-level outcomes: clinical mastitis, removal from the herd, and Dairy Herd Improvement Association (DHIA) test-day milk yield and SCC measures during the first 120 d in milk (DIM). Two days before planned dry-off, cows in each of 7 herds were randomly allocated to BDCT, culture-guided SDCT (cult-SDCT), or algorithm-guided SDCT (alg-SDCT). At dry-off, BDCT cows received an intramammary antibiotic (500 mg of ceftiofur hydrochloride) in all 4 quarters. Antibiotic treatments were selectively allocated to quarters of cult-SDCT cows by only treating quarters from which aseptically collected milk samples tested positive on a rapid culture system after 30 to 40 h of incubation. For alg-SDCT cows, antibiotic treatments were selectively allocated at the cow level, with all quarters receiving antibiotic treatment if the cow met at least one of the following criteria: (1) any DHIA test with a somatic cell count >200,000 cells/mL during the current lactation, and (2) ≥2 clinical mastitis cases during the current lactation. All quarters of all cows were treated with an internal teat sealant. Clinical mastitis and removal from the herd events (i.e., culling or death) and DHIA test-day data from dry-off to 120 DIM were extracted from herd records. Hazard ratios (HR) for the effect of treatment group on clinical mastitis and removal from the herd during 1 to 120 DIM were determined using Cox proportional hazards regression. The effects of treatment group on test-day loge-transformed SCC and milk yield were determined using linear mixed models. Final models indicated that either SDCT program was unlikely to increase clinical mastitis risk (HRcult-SDCT/BDCT = 0.82, 95% CI: 0.58, 1.15; HRalg-SDCT/BDCT = 0.83, 95% CI: 0.63, 1.09) or test-day logeSCC (cult-SDCT minus BDCT = 0.05, 95% CI: −0.09, 0.18; alg-SDCT minus BDCT = 0.07, 95% CI: −0.07, 0.21). Risk of removal from the herd and test-day milk yield were similar between treatment groups. Findings from this study indicate that culture- or algorithm-guided SDCT can be used at dry-off without negatively affecting cow health and performance in early lactation.
Bibliographical noteFunding Information:
We are very grateful for the participation and tremendous cooperation by owners and staff at the seven participating dairies. We also thank the technicians who assisted at each study site: California (Maria Amaral, Gema Camacho, Pablo Duque, Pallavi Nahata, Kruthika Patel, Maria Jose Perez, Cinthya Tovar and Juanita Zaragoza), Iowa (Jordan Stratman, Courtney Behrens, Emily Schwake, and Austin Ashbacher), Minnesota (Kelli Bowman, Joshua Brown, Pedro Paulo Cecillio Ferro, Chandra Dahike, Kaylan Risacher and Victor Moro Taveira), and New York (Lauren Pitman and Michaela Thomas). S. M. Rowe was involved in local and multi-site coordination, fieldwork, laboratory work, data management, statistical analysis, and manuscript preparation; S. M. Godden was involved in study conceptualization, herd recruitment in Minnesota and Wisconsin, supervision of fieldwork, and manuscript editing; P. J. Gorden and A. Lago were involved in study conceptualization, herd recruitment, local site coordination, fieldwork, and manuscript editing; D. V. Nydam was involved in study conceptualization, New York herd recruitment, local site coordination, and manuscript editing; A. K. Vasquez was involved in fieldwork, local site coordination, and manuscript editing; E. Royster was involved in study conceptualization and manuscript editing; J. Timmerman was involved in laboratory work and manuscript editing; and M. J. Thomas was involved in local site coordination, fieldwork, and manuscript editing. This study was funded by the USDA-National Institute of Food and Agriculture (Award # 2018-67015-28298) and was supported by an in-kind donation of product (Spectramast DC and Orbeseal) from Zoetis (Parsippany, NJ). The Minnesota Easy 4Cast plate is manufactured by the University of Minnesota (St. Paul, MN). However, the study investigators have no financial interest in the sale of this plate. The authors have not stated any conflicts of interest.
- clinical mastitis
- on-farm culture
- selective dry-cow therapy
PubMed: MeSH publication types
- Journal Article
- Randomized Controlled Trial, Veterinary