Age and weight are key factors that influence time of puberty
in heifers. Heifers should attain 60% of their mature weight
prior to breeding. Because selection pressure on growth has
increased mature cow size, producers may tend to underestimate
future mature size. Producers that score heifer reproductive
tracts at 50 to 60 days prior to breeding have a true measure
of physiological maturity and time to adjust rations prior to
breeding. If 50% of heifers have a tract score of 3 or greater 50
to 60 days prior to breeding, estrous synchronization programs
tend to be more successful. Protocols including a progestin
such as MGA or CIDR will induce some prepubertal heifers to
cycle.