Detection of chromosomal segments underlying scrotal circumference in ram lambs and age at onset of puberty in ewe lambs

Abstract

Scrotal circumference (SC) is highly correlated with total sperm production and quality of the produced semen. In ewe lambs, puberty is an important reproductive trait and extreme delay in reaching puberty will have a negative effect on breeding efficiency. To identify genomic regions (QTL) underlying variation in SC and age at onset of puberty in ewe lambs (AP), a whole genome scan was performed with 169 microsatellites covering the ovine autosomes. Progeny (360 animals) from six half-sib families in a population of Kermani sheep, an indigenous fat tailed sheep breed in south-east of Iran, were recorded for SC and AP. Linkage analysis using the interval mapping approach indicated a total of 21 QTL for the studied traits on nine chromosomes (OAR1, 2, 3, 5, 6, 9, 11, 18 and 24), including a 5% genome wide significant QTL for SC on OAR5. There was evidence for the overlap of QTL affecting SC and AP on OAR5 and OAR9. The size of the QTL effect ranged from 0.8 to 1.6 in units of the phenotypic standard deviation. Although QTL for testis size in ram lambs have been mapped, this is the first report of QTL for age at onset of puberty in ewe lambs. Pursuing the underlying causes of these QTL may shed light on the molecular aspects of male and female reproductive development in sheep.