Over a 3-year period (1976-1978), heifer calves either were not implanted
or were implanted between 2 and 5 months of age. In 1977, the study also
included heifers implanted at birth. Implanting at birth increased the
percentage of heifers open as yearlings. More implanted heifers tended to
be open as 2- to 5-year-olds than control heifers, but the differences were
not statistically significant. Implanting of the heifers had no effect
on weight gains of their calves.