Sources of variation in replacement rate in Bharat Merino sheep

The life-time performance data on 1172 lambing records of ewes available from 1982 to 1989 have been utilized to investigate the role of sire, season, year and parity of lambing in influencing sex-ratio, mortality and replacement rate. The sex-ratio among progeny of different sires over periods and seasons did not differ significantly. The average incidence of mortality and culling in female lambs before first lambing was 39.1 and 16.4 per cent, respectively. The differences in mortality rate due to sires and periods were significant and the influence of season and parity of lambing was non-significant. The percentage of female lambs reaching the age of first lambing, was 22.7 and 44.5 based on total births and the female births, respectively. The sires contributed significantly towards the variation in replacement rate, while season, period and parity of lambing did not contribute significantly. The study indicated that the gains were possible in replacement rate as well as in mortality rate through ram lamb selection and through improvement in managemental conditions and health cover.