Furthermore, in AI-NS group, the median days to pregnancy for heifers with RTS 1 and 2, and 3 were 25 and 28.5 days respectively. In NSO group, the median days to pregnancy for heifers with RTS 1 and 2, and 3 were 60 and 60 days, respectively. Perhaps the use of synchronization protocol might have induced estrus and ovulation in pre- and peripubertal heifers in AI-NS group, and helped to achieve higher pregnancy rate. It should also be noted that proportion of heifers with RTS 3 or less were similar for NSO and AI-NS groups.