THE INFLUENCE OF TIME OF INSEMINATION RELATIVE TO TIME OF OVULATION ON FARROWING FREQUENCY AND LITTER SIZE IN SOWS, AS INVESTIGATED BY ULTRASONOGRAPHY

The objective of this experiment was to identify the optimal time of i nsemination relative to the time of ovulation, based on ultrasonograph ic detection of embryonic survival at 10 days after ovulation, number of sows farrowing, and litter size. Furthermore, the possible value of the interval from weaning to onset of estrus for prediction of the ti me of ovulation was examined. Crossbred sows (n=143) that had farrowed 2 to 9 litters were weaned (Day 0) and observed for estrus every 8 h from Day 3 until end of estrus. Ultrasonography was performed every 6 h, from 12 h after onset of estrus until ovulation had been observed. The sows were inseminated once at various time intervals from ovulatio n. At Day 16, 25 of the sows were slaughtered and their uteri were flu shed for embryos. In the remaining sows, the number of viable and dead piglets and mummified fetuses per sow was recorded at farrowing, with the sum of the 3 constituting the total number of piglets born per so w. The highest number of embryos recovered per sow was found after ins emination during the interval from 24 h before to 4 h after ovulation. The lowest frequency of non-pregnant sows and the highest total numbe r of piglets born per sow were found after insemination from 28 h befo re to 4 h after ovulation. Consequently, the optimal time for insemina tion was found to be in the interval 28 h before to 4 h after ovulatio n. The interval;from weaning to onset of estrus and from onset of estr us to ovulation were negatively correlated, allowing a rough predictio n of the time of ovulation from the interval from weaning to onset of estrus. (C) 1997 by Elsevier Science Inc.