Effect of somatic cell count level on functional longevity in Valle del Belice dairy sheep assessed using survival analysis

V. Riggio*, D. O. Maizon, B. Portolano, H. Bovenhuis, J. A. M. van Arendonk

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

The objectives of this study were to evaluate the effect of somatic cell count (SCC) on functional longevity and to estimate the heritability of functional longevity using survival analysis in Valle del Belice dairy sheep. A total of 4,880 lactations of 2,190 ewes from 11 flocks were used. In this study, SCC was considered as an indication of subclinical mastitis. In case of clinical cases, identified by the technicians at milking time, test-day weights and milk samples of those ewes were not considered. Somatic cells were analyzed as counts, without any transformation, and were grouped in 3 classes based on the observed SCC maximum (mxSCC). The mxSCC classes, expressed as 10(3) cells/mL, were classified as 1 if mxSCC = 1,000. An increase in SCC was associated with an increased hazard of being culled. Ewes in the highest class of SCC on a test-day had a 20% higher hazard of being culled than those in the lowest class. Therefore, SCC played a role in culling decisions of Valle del Belice dairy sheep farmers. The heritability estimate for functional longevity was 7% on the logarithmic scale and 11% on the real scale, indicating that selection for this trait is possible in sheep. The flock-year-season effect explained 19% of the variation on the logarithmic scale and 27% of the variation on the real scale.

Original languageEnglish
Pages (from-to)6160-6166
Number of pages7
JournalJournal of Dairy Science
Volume92
Issue number12
DOIs
Publication statusPublished - Dec 2009

Keywords

  • somatic cell count
  • longevity
  • survival analysis
  • dairy sheep
  • GENETIC-PARAMETERS
  • PRODUCTIVE LIFE
  • SUBCLINICAL MASTITIS
  • CATTLE
  • MILK
  • SELECTION
  • HOLSTEIN
  • SCORE
  • COWS
  • TRAITS

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