Contents This study examined the extent to which prolonged farrowing and parity are associated with plasma oxytocin concentrations and follicular development of oestrous sows during subsequent insemination. A total of 30 sows were allocated to two groups based on farrowing duration: (i) SHORT (n=14): 159 +/- 29min, (ii) LONG (n=16): 533 +/- 190min. The sows were also divided into two parity classes: (i) YOUNG (n=14): parity 2.5 +/- 0.8, (ii) OLD (n=16): parity 6.4 +/- 2.3. After weaning, the ovaries were examined daily with transrectal ultrasound. On the second day of oestrus, blood samples were collected for oxytocin (OT) assay at -15, -10, -5, 0, +1, +2, +3, +4, +6, +8, +10, +15, +20, +25, +30, +40, +50 and +60min with a boar contact between 0 and +10min. Boar presence stimulated an increase in OT concentrations (p