Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 407973
Title Time-to-event analysis of mastitis at first-lactation in Valle del Belice ewes
Author(s) Portolano, B.; Firlocchiaro, R.; Kaam, J.B.C.H.M. van; Riggio, V.; Maizon, D.O.
Source Livestock Science 110 (2007)3. - ISSN 1871-1413 - p. 273 - 279.
DOI http://dx.doi.org/10.1016/j.livsci.2006.11.010
Department(s) Animal Breeding and Genetics
WIAS
Publication type Refereed Article in a scientific journal
Publication year 2007
Keyword(s) somatic-cell counts - clinical mastitis - dairy-cows - bayesian-analysis - survival analysis - norwegian cattle - milk-yield - sheep - lactation - selection
Abstract A time-to-event study for mastitis at first-lactation in Valle del Belice ewes was conducted, using survival analysis with an animal model. The goals were to evaluate the effect of lambing season and level of milk production on the time from lambing to the day when a ewe experienced a test-day with a recorded SCC greater than or equal to 750,000 cells/ml, and to estimate, for this trait, its heritability and the percentage of variation explained by the flock-year of lambing effect. A dataset with 2468 first-lactation records, collected from 1998 to 2003 in Valle del Belice ewes allocated in 17 flocks, was used. The Cox model used included lambing season and total milk yield adjusted for lactation length as fixed effects and flock-year of lambing effect and individual additive genetic effect as random effects. In total 40.5% of the records were censored. Results indicated that ewes lambing from April to July were at a higher risk of mastitis than those lambing from August to November (conventional season), and that ewes in the highest class of milk production were at a higher risk of mastitis than those in the lowest level. The heritability for the time interval between lambing and first test-day with mastitis was 3% on the logarithmic scale and 4% on the real scale. The proportion of variation, in the time interval between lambing and first test-day with mastitis, explained by the flock-year of lambing effect was 19% on the logarithmic scale and 27% on the real scale; this seems to stress the importance of flock management.
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