Each species must attain a certain optimal
size before embarking on the responsibilities
and challenges of reproduction. The
period from weaning to puberty is usually
the period of greatest absolute growth rate,
and is characterized by the animal utilizing
its nutritional resources to the full to attain
a size which will enable it to reproduce suc-
Prenatal and Postnatal Growth 199
cessfully. It is this period which forms the
main focus of animal production systems.
In some species, this period is extended
over several years and growing seasons,
during which time the animal learns how
to utilize its feed resources, defend itself
from predators and develop the social skills
of its species.