title: The selective treatment of clinical mastitis based on on-farm culture results: I. Effects on antibiotic use, milk withholding time, and short-term clinical and bacteriological outcomes.
abstract: 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 24h 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.
authors.affiliation: Department of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, Saint Paul, Minnesota 55108, USA. alfonso.lago@gmail.com
authors.forename: A
authors.initials: A
authors.lastname: Lago
authors.forename: S M
authors.initials: SM
authors.lastname: Godden
authors.forename: R
authors.initials: R
authors.lastname: Bey
authors.forename: P L
authors.initials: PL
authors.lastname: Ruegg
authors.forename: K
authors.initials: K
authors.lastname: Leslie
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D001431:Bacteriological Techniques / Q000662:veterinary; D002417:Cattle; D002514:Cephapirin / Q000008:administration & dosage / Q000627:therapeutic use*; D003612:Dairying / Q000379:methods; D005260:Female; D007774:Lactation / Q000187:drug effects / Q000502:physiology*; D008414:Mastitis, Bovine / Q000175:diagnosis / Q000188:drug therapy* / Q000382:microbiology / Q000503:physiopathology / Q000628:therapy; D013997:Time Factors; D017211:Treatment Failure; D016896:Treatment Outcome
chemical_list: D000900:Anti-Bacterial Agents; D002514:Cephapirin