Enquête éco-pathologique continue : facteurs de risque des mammites de la vache laitière. I. Analyses multidimensionnelles sur données d'élevage

An epidemiological study about mastitis in French dairy herds, supported by an ecopathological survey is described. The aim of this work was to explain variations of the annual frequencies of clinical mastitis in the farms studied and of milk somatic cell counts as predictive of the infectious status of the mammary gland. Milk cell counts were expressed as annual percentages of cell results < 2.105 cells / mL (0.2 CEL) and > 1.106 cells / mL (1.0 CEL) in each herd. Twenty-nine herds were studied from June 1979 to July 1981 (22 to 92 cows per herd, Normande and Pie-Noire breeds) and, for the first time, the influence of 88 variables upon clinical mastitis, 0.2 CEL and 1.0 CEL was performed by multidimensional methods. These analyses led to the evidence of two kinds of factors linked with mastitis occurrences or milk cell-counts: 1) Not well defined factors: geoclimatic, racial, links between production traits, extra-mammary pathology, susceptibility to mastitis and cells-counts; to elucidate if they were factors really linked with mammary infections, a complementary analysis is described as necessary (cf. second part of this study). 2) Risk or protective factors, which appeared as: — absence of at least one annual examination of the milking machine (risk factor for clinical mastitis) — udder washing with individual towels, associated with enough straw for bedding (protective factor against mastitis) — teat dipping (associated with low milk cell-counts) Other prophylactic methods appeared without any effect. In the discussion, main difficulties of an epidemiological approach to the mastitis problem are summarized. A convenient hygiene-prophylaxis interaction is necessary to control mammary infections in dairy herds.