Servizio Comunitario di Informazione in materia di Ricerca e Sviluppo - CORDIS

QTL for mastitis resistance in the Sarda x Lacaune population

Milk somatic cell count (SCC) was considered as the trait pertaining to mastitis resistance. Individual milk samples were collected bimonthly at evening and morning milking in the first four lactations to determine SCC. Final data consisted of individual milk SCC of the 969 ewes, measured about 12 times per lactation at morning and evening milkings, approximately every 2 to 3 weeks from December to July, in 2000, 2001, 2003 and 2004 (parity 1 to 4, respectively). After data checking, 3,183 lactations and 32,929 elementary daily values of SCS from 917 ewes were used.

Elementary SCC were converted to SCS, after classic log-transformation. Morning and evening values were averaged to a single day measure. Analyses were done either on lactation means of daily SCS (LSCS), either directly in test day models.

Traits considered were therefore:
- LSCS in parity 1 to 4 considered as four different traits (LSCS1 to LSCS4),

- LSCS considered as a repeated trait across the four lactations (LSCS1234-rep),

- elementary SCS considered as a repeated trait (SCS 1234-TD) within lactation and across years.

For the 6 somatic cell count (SCC) traits (LSCS1, LSCS2, LSCS3, LSCS4, LSCS1234-rep, SCS 1234-TD), a total of 11 QTL were found at the genome wise significance threshold with a suggestive linkage (p=0.038). Out of these results, QTL with a high confidence level (several traits; genome wise significance threshold; position and LRTmax profiles similar across traits) were detected on two chromosomes: OAR6 (closest markers BMS0360) and OAR13 (closest markers INRA133 and BMC1222). Effect of the latter QTL varied from 0.27 to 1 standard deviation.


Rachel RUPP, (Researcher)
Tel.: +33-5-61285180
Fax: +33-5-61285353