Development of a Genotype for Out-of-Season Lambing

A flock derived from Polled Dorset x Romney sheep has been selected for advanced lambing date for 20 years. After 15 years over 90% of selected ewes displayed the ability to lamb in autumn, Genetic parameters have been analysed and high heritability (0.23) and repeatability (0.36) estimated. Current research is aimed at selection of divergent flocks based on use of breeding values for date of lambing and the elucidation of what has altered in the physiological and endocrinological mechanisms controlling the onset of breeding season and also the identification of early indicator traits in the male and female progeny, Preliminary data indicates that date of puberty in ewe lambs may be a good indicator on the female side.