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RESEARCH PRODUCT

Analyses of udder health in Valle del Belice dairy sheep using SCC

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description

Intramammary infections (IMI) are a complex of inflammatory diseases of the mammary gland. Mastitis is one of the most frequent IMI affecting small dairy ruminants. Direct selection against clinical mastitis is difficult because mastitis in not widely recorded; therefore, somatic cell count (SCC) is promoted as selection criterion for mastitis resistance. A dataset containing 2,457 first- lactation Valle del Belice ewes from 14 flocks recorded from 1998 to 2003 was analysed. In total 116 sires with at least four daughters with a record were included in the pedigree file. Test-day IMI events were coded as a binary trait using a SCC cut-off value of 750,000 cells/ml. Analyses of risk factors for the binary IMI trait were based on a logistic regression model. The herd effect was the major risk factor for IMI. The risk of culling due to IMI increased for late season of lambing. A single trait threshold sire model was applied. The heritability calculated using a logit function was 0.16±0.072 very close to the expected value of 0.14 calculated with Dempster and Lerner’s formula treating IMI as a continuous variable.