Canadian National Dairy Study: Herd-level milk quality

• Published in: Journal of dairy science Vol. 101; no. 3; pp. 2679 - 2691
• Main Authors: Bauman, C.A., Barkema, H.W., Dubuc, J., Keefe, G.P., Kelton, D.F.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.03.2018
• Subjects: Animals; Canada; Canada - epidemiology; Cattle; Dairying; Female; mastitis; Mastitis, Bovine - epidemiology; Mastitis, Bovine - microbiology; Milk - microbiology; Milk - standards; milk quality; Prevalence; Prototheca - isolation & purification; somatic cell count; Staphylococcus aureus; Staphylococcus aureus - isolation & purification; Streptococcus agalactiae - isolation & purification; Canada; mastitis; Staphylococcus aureus; somatic cell count; milk quality
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.2017-13336

The objective of this study was to estimate Canadian national milk quality parameters and estimate the bulk tank milk (BTM) prevalence of 4 mastitis pathogens, Staphylococcus aureus, Streptococcus agalactiae, Mycoplasma bovis, and Prototheca spp., on Canadian dairy farms. A questionnaire was sent to all Canadian dairy producers. Of the 1,062 producers who completed the questionnaire, 374 producers from across the country were visited and milking hygiene was assessed. Farm-level milk quality data for all Canadian dairy producers was collected from the provincial marketing boards and combined with the questionnaire and farm visit data. In addition, a BTM sample was collected either during the farm visit or by the marketing board in November of 2015 and was tested for 4 major mastitis pathogens using the PathoProof Mastitis Major 4 PCR Assay (Thermo Fisher Scientific Inc., Waltham, MA). Apparent herd-level prevalence was 46% for S. aureus, 6% for Prototheca spp., 0% for M. bovis, and 0% for Strep. agalactiae. Due to the low prevalence of M. bovis and Strep. agalactiae and a lack of significant factors associated with farms testing positive for Prototheca spp., an association analysis could only be carried out for Staph. aureus-positive farms. Factors associated with Staph. aureus-positive farms were not fore-stripping cows before milking (odds ratio = 1.87), milking with a pipeline system (odds ratio = 2.21), and stall bases made of a rubberized surface (mats and mattresses), whereas protective factors were using blanket dry cow therapy (odds ratio = 0.49) and applying a tag or visible mark on cows known to have chronic mastitis infections (odds ratio = 0.45). The Canadian national production-weighted geometric mean somatic cell count was determined to be 208,000 cells/mL. This is the first national dairy study conducted in Canada. Participating farms had higher milk yield; were more likely to have a loose housing system, parlor, or automated milking system; and had lower weighted mean BTM somatic cell count than the national level. Sampling larger farms with better milk quality means the apparent prevalence of the 4 mastitis pathogens likely underestimates the true levels.