Evaluation of selective dry cow treatment following on-farm culture: Milk yield and somatic cell count in the subsequent lactation

Abstract

Compared with blanket dry cow therapy (DCT), the selective antimicrobial treatment of cows based upon on-farm culture results has the potential to reduce the amount of antimicrobials used in dairy production. The objective of the current study was to determine the effect of a Petrifilm (3M Canada, London, Ontario) on-farm culture-based selective DCT program on milk yield and somatic cell count (SCC) in the following lactation. A total of 729 low-SCC (<200,000 cells/mL) cows from 16 commercial dairy herds with a low bulk tank SCC (<250,000 cells/mL) were randomly assigned to receive either blanket DCT or Petrifilm-based selective DCT. Cows belonging to the blanket DCT group were infused with a commercial DCT product and an internal teat sealant (ITS) at drying off. Using composite milk samples collected on the day before drying off, cows in the selective DCT group were treated at drying off based on the results obtained by the Petrifilm on-farm culture system with DCT and ITS (Petrifilm culture positive) or ITS alone (Petrifilm culture negative). Milk test-day records for the following lactation were obtained from Dairy Herd Improvement for all cows enrolled in the trial. Repeated measures linear mixed models were used to assess the effect of study group (blanket or selective DCT) on test-day milk production and natural logarithm of SCC over the first 180 d of the subsequent lactation. According to the final multivariable models, when low-SCC cows were selectively treated with DCT at drying off based on results obtained using the Petrifilm on-farm culture system, no effect on milk production (least squares means for blanket DCT = 39.3 kg vs. selective DCT = 39.0 kg) or natural logarithm of SCC (least squares means for blanket DCT = 3.95 vs. selective DCT = 3.97) was observed in the subsequent lactation when compared with cows receiving blanket DCT. The results of this study indicate that selective DCT based on results obtained by the Petrifilm on-farm culture system enabled a reduction in the use of DCT without negatively affecting milk production and milk quality.

Farmers’ attitude toward the introduction of selective dry cow therapy

“…During this year, increasingly more farmers began with SDCT, although no implementation guideline existed. No dramatic increase in mastitis incidence and related AMU occurred with implementation of SDCT, although earlier work had shown a possible increase in IRCM and SCM when SDCT was applied (Scherpenzeel et al, 2014;Cameron et al, 2015). This difference may be due to these studies using more stringent criteria for DCT, such as SCC at the last milk recording before drying-off and on-farm culturing as criteria to select cows for DCT.…”

The use of national-level data to describe trends in intramammary antimicrobial usage on Irish dairy farms from 2003 to 2015

“…Selection based on SCC at the last milk recording before drying off gives a substantial reduction in antimicrobial use, but leads to an increase in clinical mastitis, subclinical mastitis, and culture-positive quarters (Scherpenzeel et al, 2014). In contrast, no adverse effect was observed on postcalving IMI or clinical mastitis (Cameron et al, 2014) or on milk production or SCC (Cameron et al, 2015) in the subsequent lactation when Petrifilm-based on-farm culture systems were used to allow targeting of selective DCT. The use of teat sealant, in place of an antimicrobial, is also an option for selective DCT.…”

Effects of reduced intramammary antimicrobial use during the dry period on udder health in Dutch dairy herds

“…With SDCT, only those cows most likely to have an IMI at dry-off are treated with intramammary antimicrobials. Several cow level variables such as SCC, bacteriologi-cal culture, and clinical mastitis history are considered when selecting cows likely to have an IMI at dry-off (Torres et al, 2008;Cameron et al, 2015;Kiesner et al, 2016).…”