title: The selective treatment of clinical mastitis based on on-farm culture results: II. Effects on lactation performance, including clinical mastitis recurrence, somatic cell count, milk production, and cow survival.
abstract: 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 24h 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.
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 / Q000627:therapeutic use*; D001431:Bacteriological Techniques / Q000662:veterinary; D002417:Cattle; D002452:Cell Count / Q000662:veterinary; D002514:Cephapirin / Q000627:therapeutic use*; D003612:Dairying / Q000379:methods; D005260:Female; D007774:Lactation / Q000187:drug effects* / Q000502:physiology; D008414:Mastitis, Bovine / Q000188:drug therapy* / Q000382:microbiology / Q000401:mortality / Q000503:physiopathology; D008892:Milk / Q000166:cytology* / Q000592:standards; D012008:Recurrence
chemical_list: D000900:Anti-Bacterial Agents; D002514:Cephapirin