The effect of farrowing duration and parity on preovulatory follicular size and oxytocin release of sows at subsequent oestrus

This study examined the extent to which prolonged farrowing and parity are associatedwith plasma oxytocin concentrations and follicular development of oestroussows during subsequent insemination. A total of 30 sows were allocated to twogroups based on farrowing duration: (i) SHORT (n = 14): 159 ± 29 min, (ii) LONG(n = 16): 533 ± 190 min. 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 ofoestrus, 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 +60 min with a boar contactbetween 0 and +10 min. Boar presence stimulated an increase in OT concentrations(p < .05). During boar presence, OT in the LONG group was higher than in the SHORTgroup (p < .01). The sows in the OLD group had a longer farrowing duration than inthe YOUNG group (p < .05). OT levels and diameters of follicles were more relevantfor parity than was the duration of farrowing. We therefore conclude that the OTlevels and follicular development of oestrous sows are associated due to parity butdifficult to be predicted from the duration of previous farrowing.