Periovulatory hormone profiles in relation to embryonic development and mortality in pigs

The timing between the onset of oestrus and the preovulatory Luteinizing hormone (LH) peak in gilts was investigated. The LH peak was most frequently observed approximately 1Oh after the onset of oestrus, although large variations from 20h before to more than 24h after the onset of oestrus were noticed. The time interval between the LH peak and ovulation, however, was rather constant and so a large variation with regard to the time interval between the onset of oestrus and ovulation was observed. Insemination of pigs at a fixed time interval after the onset of oestrus resulted in conceptions with sperm of variable age. The results suggest a higher incidence of embryonic mortality with an increasing interval between the time of insemination and ovulation. The rate of development of pig embryos between day 3 and 7 of pregnancy was studied with respect to the time of ovulation. The results indicate that pig embryos double their number of cells every 11 hours.