Effects of the Litter of Origin and Rearing Litter Size on the Reproductive Potential of Replacement Gilts

This study aimed to assess how prenatal and early postnatal conditions affect the future reproductive performance of young female pigs (gilts). Female piglets were selected from sows in their 3rd and 4th parity. Vaginal and cervical length (VCL) was measured using a catheter during the first (VCLI) and second (VCLII) oestrus. Gilts were classified based on their litter of origin: fewer than 16 piglets (OS), 16-18 piglets (OM), and more than 18 piglets (OL). The longest VCLI was found in gilts from the OM group, significantly differing from both the OS and OL groups. For VCLII, significant differences were found between OS and the other groups, with OM and OL showing greater values. Litter size at birth did not negatively affect later reproductive potential. A positive correlation was found between VCLII and the number of piglets in the first litter, indicating that the larger the litter of origin, the higher the reproductive productivity of the gilt. The results highlight that development between the first and second oestrus is critical for vaginal and cervical growth, which, in turn, reflects future reproductive performance. These findings suggest that early life conditions, particularly litter of origin, play a key role in determining the productivity of replacement gilts.