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.

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.

Lago A ，Godden SM ，Bey R ，Ruegg PL ，Leslie K ... -  《-》

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.

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.

Lago A ，Godden SM ，Bey R ，Ruegg PL ，Leslie K ... -  《-》

Risk factors associated with short-term post-treatment outcomes of clinical mastitis.

The objectives of this study were to characterize 60-d outcomes after treatment of mild (abnormal milk) and moderate (abnormal milk and abnormal udder) cases of clinical mastitis (CM) occurring in a single quarter of cows on Wisconsin farms (n=4) and to determine risk factors associated with those outcomes. Duplicate milk samples were collected from the affected quarter of each cow for microbiological analysis at the onset of CM (PRE) and 21 d later (POST). Cows were treated only in the affected quarter using an intramammary product containing 125 mg of ceftiofur. Bacteriological cure was defined as absence of pathogens in the POST sample obtained from the enrolled quarter. Recurrence was defined for the cow when CM occurred after the milk-withholding period for the enrolled case of CM. Retention in the herd was defined when a cow was retained within the herd for the 60-d follow-up period. Somatic cell count reduction (SCCR) was defined at the cow level as somatic cell count (SCC) below 200,000 cells/mL at the Dairy Herd Improvement Association test day occurring between 21 to 55 d post-treatment. The effects of farm, days in milk, parity, severity, microbiological diagnosis at PRE, previous milk yield, previous SCC, previous occurrence of CM and treatment duration on selected post-treatment outcomes were assessed using Chi-squared analysis and logistic regression. Microbiological results at PRE were distributed as: Escherichia coli (n=14), Klebsiella spp. (n=11), Enterobacter spp. (n=8), Serratia spp. (n=7), other gram-negative species (n=3), Streptococcus spp. (n=25), coagulase-negative staphylococci (n=4); Staphylococcus aureus (n=1); Streptococcus agalactiae (n=1), other gram-positive species (n=9), and culture negative (n=60). Treated quarters were more likely to experience bacteriological cure when the cow experienced CM for the first time in the lactation and when no pathogen was recovered from PRE milk samples obtained from the enrolled quarter. Parity and bacteriological cure were associated with the probability of recurrence. Greater milk yield at previous Dairy Herd Improvement test was the most important predictor for retention within the herd. When SCC before CM was >200,000 cells/mL the probability of having SCCR after treatment was decreased. When the case experienced bacteriological cure, the cow was less likely to experience recurrent cases and was more likely to have SCCR below 200,000 cells/mL. Post-treatment outcomes, such as recurrence and SCCR, are strongly associated with bacteriological cure and, when monitored, can be used to help determine if a treatment has been successful. Information about the etiology of CM, history of clinical and subclinical mastitis, and parity are useful to review when making strategic treatment decisions.

Pinzón-Sánchez C ，Ruegg PL 《-》

Effects of prepartum intramammary antibiotic therapy on udder health, milk production, and reproductive performance in dairy heifers.

Borm AA ，Fox LK ，Leslie KE ，Hogan JS ，Andrew SM ，Moyes KM ，Oliver SP ，Schukken YH ，Hancock DD ，Gaskins CT ，Owens WE ，Norman C ... -  《-》

Factors affecting cure and somatic cell count after pirlimycin treatment of subclinical mastitis in lactating cows.

Deluyker HA ，Van Oye SN ，Boucher JF 《JOURNAL OF DAIRY SCIENCE》