The objective of this multi-state, multi-herd clinical trial was to report on the efficacy of using an on-farm culture system to guide strategic treatment decisions in cows with clinical mastitis. The study was conducted in 8 commercial dairy farms ranging in size from 144 to 1,795 cows from Minnesota, Wisconsin, and Ontario, Canada. A total of 422 cows affected with mild or moderate clinical mastitis in 449 quarters were randomly assigned to either (1) a positive-control treatment program or (2) an on-farm culture-based treatment program. Quarter cases assigned to the positive-control group received immediate on-label intramammary treatment with cephapirin sodium. Quarters assigned to the culture-based treatment program were not treated until the results of on-farm culture were determined after 18 to 24. h of incubation. Quarters in the culture-based treatment program that had gram-positive growth or a mixed infection were treated according to label instruction using intramammary cephapirin sodium. Quarters assigned to the culture-based treatment program that had gram-negative or no-growth did not receive intramammary therapy. It was already reported in a companion paper that the selective treatment of clinical mastitis based on on-farm culture results decreases antibiotic use by half and tends to decrease milk withholding time without affecting short-term clinical and bacteriological outcomes. The present article reports on long-term outcomes of the aforementioned study. No statistically significant differences existed between cases assigned to the positive-control program and cases assigned to the culture-based treatment program in risk and days for recurrence of clinical mastitis in the same quarter (35% and 78 d vs. 43% and 82 d), linear somatic cell count (4.2 vs. 4.4), daily milk production (30.0 vs. 30.7. kg), and risk and days for culling or death events (28% and 160 d vs. 32% and 137 d) for the rest of the lactation after enrollment of the clinical mastitis case. In summary, the selective treatment of clinical mastitis based on on-farm culture resulted in no differences in long-term outcomes, such as recurrence of clinical mastitis in the same quarter, somatic cell count, milk production, and cow survival for the rest of the lactation after clinical mastitis.
Bibliographical noteFunding Information:
The authors thank Daniel Hagman, Grant Williams, Joseph Hochhalter, Krista Steffenhagen, Mackenzie Jones, Margaret Perala, Maya Kuratomi, and Megan Becker for the project implementation work and the Udder Health Laboratory Staff at the University of Minnesota, College of Veterinary Medicine; Danielle Davignon, Carlo Spanu, Dhananjay Apparao, José Pantoja, Leane Oliveira, and Martín Pol for the project implementation work and Carol Hulland for the laboratory work at the University of Wisconsin, Dairy Science Department; and Amy Stanton, Cindy Todd, Erin Vernooy, and Nicole Perkins for the project implementation work and Anna Bashiri for the laboratory work at the University of Guelph, Ontario Veterinary College (Canada). We also recognize the input provided by John Fetrow (University of Minnesota, College of Veterinary Medicine, Saint Paul), Michael Oakes (University of Minnesota, School of Public Health, Minneapolis), Paul Rapnicki (University of Minnesota, College of Veterinary Medicine), and Steven Stewart (University of Minnesota, College of Veterinary Medicine). A special thanks to the dairy owners and farm personnel for providing their herds and labor for this project. The study was possible thanks to funding provided by the Minnesota Agriculture Experimental Station, Fort Dodge Animal Health Inc. (Fort Dodge, IA) and Dairy Farmers of Ontario. In particular, the authors remember Dr. Jon Rosenberg, of Fort Dodge Animal Health Inc., who was especially supportive of this study.
- Clinical mastitis
- On-farm culture
- Selective treatment