ABSTRACT: Studies in numerous species provide
evidence that diet during development can mediate
physiological changes necessary for puberty. In cattle,
several studies have reported inverse correlations between
postweaning growth rate and age at puberty and
heifer pregnancy rates. Thus, postweaning growth rate
was determined to be an important factor affecting age
of puberty, which in turn influences pregnancy rates.
This and other research conducted during the late
1960s through the early 1980s indicated puberty occurs
at a genetically predetermined size, and only when
heifers reach their target BW can increased pregnancy
rates be obtained. Guidelines were established indicating
replacement heifers should achieve 60 to 65% of
their expected mature BW by breeding. Traditional approaches
for postweaning development of replacement
heifers used during the last several decades have primarily