The importance of birth weight for survival until weaning and for development until the selection time was
confi rmed in this study. Since birth weight was associated with ADWG, the expectation was that puberty onset would happen
earlier in gilts with greater ADWG. In other studies, gilts with greater growth rates reached puberty earlier if stimulated at
an early age (~140 days of age). In the present study, however, puberty onset was not affected by birth weight, probably
because gilts were exposed to boars at 165 days of age. This aspect may indicate that, after a certain age, puberty is less
dependent on growth rate. The greater risk of mortality until weaning and of not being selected for reproduction, in Light
BW gilts, contribute to economic losses in replacement gilt units. Segregation of gilts based on their birth weight can be
performed at birth or in subsequent phases. Early selection may help to reduce costs for maintaining gilts that will probably
not be selected, hence increasing the profi tability of pig production. In addition, it provides the opportunity to pay
special attention to gilts with greater potential to be future breeders. The results show that birth weight is more important
than litter size into which gilts were born for their survival until weaning, as well as for an adequate weight gain, which
will ensure their retention in the herd until the selection time. When the gilts are stimulated close to 165 days of age, age
at puberty and anoestrous rate are not affected by birth weight or litter size into which they were born.