The objective of this multi-state, multi-herd clinical trial was to evaluate 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 cultured on-farm and treated with cephapirin sodium after 18 to 24. h of incubation if they had gram-positive growth or a mixed infection. Quarters with gram-negative or no growth did not receive intramammary therapy. The proportion of quarter cases assigned to positive-control and culture-based treatments that received intramammary antibiotic therapy because of study assignment was 100 and 44%, respectively; the proportion of cases that received secondary antibiotic therapy was 36 and 19%, respectively; and the proportion of cases that received intramammary antibiotic therapy because of study assignment or secondary therapy was 100 and 51%, respectively. A tendency existed for a decrease in the number of days in which milk was discarded from cows assigned to the culture-based treatment program versus cows assigned to the positive-control group (5.9 vs. 5.2 d). No statistically significant differences existed between cases assigned to the positive-control and cases assigned to the culture-based treatment program in days to clinical cure (2.7 vs. 3.2 d), bacteriological cure risk within 21 d of enrollment (71 vs. 60%), new intramammary infection risk within 21 d of enrollment (50 vs. 50%), and treatment failure risk (presence of infection, secondary treatment, clinical mastitis recurrence, or removal from herd within 21 d after enrollment; 81 vs. 78%). In summary, the use of an on-farm culture system to guide the strategic treatment of clinical mastitis reduced intramammary antibiotic use by half and tended to decrease milk withholding time by 1 d, without significant differences in days to clinical cure, bacteriological cure risk, new intramammary infection risk, and treatment failure risk within 21 d after the clinical mastitis event.
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 (Saint Paul); 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 herd 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 Jon Rosenberg, of Fort Dodge Animal Health Inc., who was especially supportive of this study.
- Clinical mastitis
- On-farm culture
- Selective treatment