Intramammary infections and milk leakage following gradual or abrupt cessation of milking.

The objective of this study was to evaluate the effect of milking cessation method (abrupt or gradual) and daily milk yield before dry-off on milk leakage following dry-off and intramammary infections (IMI) at calving. Data from 1,086 quarters of 285 cows from 5 Ohio dairy herds were analyzed. All cows that were due to be dried off within a week were assigned to the same study group to facilitate management. Abrupt-cessation cows kept the farm's regular milking schedule through dry-off, and gradual-cessation cows were milked once daily for the final week of lactation. Aseptic technique was used to collect quarter foremilk samples at the time of enrollment (7 to 14 d before expected dry-off), the final milking before dry-off (D-O), and within 7 d of calving. Cows in the gradual-cessation group were observed for milk leakage during the period of once-daily milking. In the only herd that did not use internal teat sealants at dry-off, milk leakage after dry-off was recorded in both abrupt and gradual groups. Gradual cessation decreased milk production by 33.4% during the final week of lactation, causing milk yield at D-O to be lower for these cows compared with abrupt-cessation cows (13.2 vs. 19.8kg/d, respectively). Logistic regression models were used to model the probability of a quarter being infected at calving with any pathogen, accounting for clustering of quarters within cows and cows within herds. The final model investigating the probability of IMI at calving was stratified by parity of cows at the time of dry-off (primiparous and multiparous). Among quarters of cows that ended their first lactation, abrupt cessation of milking before dry-off and milk leakage after dry-off were associated with an increased risk of IMI at calving. Among quarters of multiparous cows, on the other hand, gradual cessation of milking before dry-off, presence of IMI at D-O, and thrice-daily milking during lactation increased the odds of IMI at calving. These results indicate that implementation of differing management practices near dry-off for different parity groups may improve mammary health within a herd.