TERQUI M, GUILLOUET P, MAUREL MC, MARTINAT-BOTTE F 2000 Relationship between peri-oestrus progesterone levels and time of ovulation by echography in pigs and influence of the interval between ovulation and artificial insemination (I.A.) on litter size. Reproduction & Development 40:1-12.
Abstract:
Two methods for the determination of ovulation were compared to one ultrasonography performed 5 times a day. Time of ovulation by ecography was 40 ± 5.8 h (mean ± SD) after the onset of oestrus. Preovulatory LH rise (two blood samples per day) began near the onset of oestrus but, in our conditions, this parameter could not be used to predict ovulation.
The basal level of progesterone (two blood samples per day) was determined with a non-linear model, the timing when progesterone rose more than one SD (0.3 ng.mL-1) coincided with the timing of ovulation determined by ecography (R² = 0.98).
This method was efficient and was used in the field trial to measure the consequences of the variability of the interval between AI and ovulation on litter size. The interval between AI and ovulation had an effect on litter size; litter size decreased by one piglet when this interval increased by 10 h.
