title: Mastitis in dairy heifers: prevalence and risk factors.
abstract: Poor udder health represents a serious problem in dairy production and has been investigated intensively, but heifers generally have not been the main focus of mastitis control. The aim of this study was to evaluate the prevalence, risk factors and consequences of heifer mastitis in Switzerland. The study included 166,518 heifers of different breeds (Swiss Red Pied, Swiss Brown Cattle and Holstein). Monthly somatic cell counts (SCCs) provided by the main dairy breeding organisations in Switzerland were monitored for 3 years; the prevalence of subclinical mastitis (SCM) was determined on the basis of SCCs ≥100,000 cells/mL at the first test date. The probability of having SCM at the first test date during lactation was modelled using logistic regression. Analysed factors included data for the genetic background, morphological traits, geographical region, season of parturition and milk composition. The overall prevalence of SCM in heifers during the period from 2006 to 2010 was 20.6%. Higher frequencies of SCM were present in heifers of the Holstein breed (odds ratio, OR, 1.62), heifers with high fat:protein ratios (OR 1.97) and heifers with low milk urea concentrations combined with high milk protein concentrations (OR 3.97). Traits associated with a low risk of SCM were high set udders, high overall breeding values and low milk breeding values. Heifers with SCM on the first test day had a higher risk of either developing chronic mastitis or leaving the herd prematurely.
authors.affiliation: Department of Animal Science, Research Institute of Organic Agriculture (FiBL), Ackerstrasse 113, 5070 Frick, Switzerland.
authors.forename: M J
authors.initials: MJ
authors.lastname: Bludau
authors.affiliation: Department of Animal Science, Research Institute of Organic Agriculture (FiBL), Ackerstrasse 113, 5070 Frick, Switzerland. Electronic address: ariane.maeschli@fibl.org.
authors.forename: A
authors.initials: A
authors.lastname: Maeschli
authors.affiliation: Department of Animal Science, Research Institute of Organic Agriculture (FiBL), Ackerstrasse 113, 5070 Frick, Switzerland.
authors.forename: F
authors.initials: F
authors.lastname: Leiber
authors.affiliation: Clinic for Ruminants, University of Berne, Bremgartenstrasse 109a, 3012 Bern, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Steiner
authors.affiliation: Department of Animal Science, Research Institute of Organic Agriculture (FiBL), Ackerstrasse 113, 5070 Frick, Switzerland.
authors.forename: P
authors.initials: P
authors.lastname: Klocke
mesh_terms: D000818:Animals; D002417:Cattle; D002452:Cell Count / Q000662:veterinary; D005260:Female; D007774:Lactation; D016015:Logistic Models; D008414:Mastitis, Bovine / Q000453:epidemiology* / Q000382:microbiology; D008954:Models, Biological; D016017:Odds Ratio; D015995:Prevalence; D012307:Risk Factors; D013557:Switzerland / Q000453:epidemiology
keywords: Dairy heifers; Prevalence; Risk factors; Somatic cell count; Subclinical mastitis