title: 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.
authors: Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada C1A 4P3. Electronic address: mcameron@upei.ca.
authors: M
authors: M
authors: Cameron
authors: Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada C1A 4P3.
authors: G P
authors: GP
authors: Keefe
authors: Faculté de médecine vétérinaire, Université de Montréal, Saint-Hyacinthe, Québec, Canada J2S 7C6.
authors: J-P
authors: JP
authors: Roy
authors: Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada C1A 4P3.
authors: H
authors: H
authors: Stryhn
authors: Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada C1A 4P3.
authors: I R
authors: IR
authors: Dohoo
authors: Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada C1A 4P3.
authors: S L
authors: SL
authors: McKenna
mesh_terms: D000818:Animals; D000890:Anti-Infective Agents / Q000008:administration & dosage*; D002170:Canada; D002417:Cattle; D002452:Cell Count / Q000662:veterinary; D003612:Dairying / Q000379:methods*; D005260:Female; D007774:Lactation / Q000187:drug effects; D016018:Least-Squares Analysis; D008414:Mastitis, Bovine / Q000188:drug therapy / Q000517:prevention & control*; D008892:Milk / Q000166:cytology*; D009864:Ontario
chemical_list: D000890:Anti-Infective Agents
keywords: Petrifilm; culture; milk yield; selective dry cow therapy; somatic cell count