Evaluation of quarter-based selective dry cow therapy using Petrifilm on-farm milk culture: A randomized controlled trial

摘要

The objective of this randomized controlled trial wasto assess the efficacy of an on-farm culture system usingPetrifilm (3M, London, ON, Canada) for targetedtreatment decisions at the quarter level at dry-off andits effects on dry period intramammary infections (IMI)and udder health and milk production in the subsequentlactation. A total of 568 cows (2,247 quarters)from 9 dairy herds with bulk tank somatic cell count<250,000 cells/mL in Québec, Canada, were systematicallyenrolled and randomly allocated to 4 groups: 2quarter-based selective (QSDCT) groups, using resultsof quarter-milk culture on Petrifilm, and 2 blanket drycow therapy (BDCT) groups. The 2 QSDCT groupsconsisted of (1) antimicrobial to infected quarters andinternal teat sealant (ITS) to healthy quarters (QSDCT/ITS); and (2) antimicrobial and ITS to infectedquarters and ITS to healthy quarters (QSDCT+ITS/ITS). The 2 BDCT groups were (1) antimicrobial aloneto all quarters (BDCT); and (2) antimicrobial and ITSto all quarters (BDCT+ITS). Quarter milk sampleswere collected at dry-off and after calving for routinebacteriological culture at the laboratory to monitorIMI; data on milk production, somatic cell count, andclinical mastitis recorded up to 120 d in milk were retrievedfrom health and DHI records. The probabilityof avoiding antimicrobial treatment in QSDCT groupswas estimated at 48.3% (95% confidence interval: 35.7,60.9). There was no significant difference between the4 treatment groups regarding acquisition of new IMI(15.9, 13.2, 15.8, and 15.1% probability for BDCT,BDCT+ITS, QSDCT/ITS, and QSDCT+ITS/ITS,respectively) or persistence of existing IMI (3.2, 2.1,3.4, and 2.7% probability, respectively) over the dryperiod. In the subsequent lactation, there was no differencebetween groups regarding incidence of clinicalmastitis (2.4, 3.7, 2.9, and 1.7% respectively for BDCT,BDCT+ITS, QSDCT/ITS, and QSDCT+ITS/ITS),mean milk somatic cell score (1.7, 2.0, 2.0, and 2.0 respectively),or mean daily milk production (43.8, 44.2,43.2, and 42.6 kg/d, respectively) during the first 120d in milk. In conclusion, QSDCT using the Petrifilmon-farm culture system to detect infected quarters atdry-off is an interesting option to decrease antibioticuse without any negative effects on udder health ormilk production in the first 120 d of the subsequentlactation compared with BDCT.