COMPARATIVE-STUDIES OF CONCEPTUS-ENDOMETRIAL INTERACTIONS IN LARGE WHITE X LANDRACE AND MEISHAN GILTS

Uterine and conceptus function were compared in mated Meishan (MS) gil ts and Large WhitexLandrace (LWxL) gilts (n = 18 breed(-1)) on Days 11 -15, inclusive, after oestrus. Comparisons of individual blastocysts r ecovered on Day 11 and Day 12 revealed a higher overall embryo surviva l in MS gilts than in LWxL gilts (100.7+/-5.0% v. 69.5+/-12.1%; P < 0. 05). Embryo survival was higher on Day 11 than on Day 12 (98.6+/-6.0% v. 71.6+/-12.6%; P < 0.05), with most of the embryo loss between these days occurring in LWxL gilts. MS conceptuses secreted less oestradiol -17 beta and radiolabelled protein on both days, but these differences were not significant. The within-litter variability in the secretion of oestradiol-17 beta and radiolabelled protein by individual conceptu ses did not differ significantly between the breeds. Concentrations of epidermal growth factor in uterine rinsings were lower in MS gilts th an in LWxL gilts on all days studied. However, two-dimensional polyacr ylamide gel electrophoresis and fluorography did not provide evidence of additional breed differences in the profile of endometrial secretor y proteins. Consistent temporal changes in the profile of the conceptu s secretory proteins were observed among all LWxL gilts and among most of the MS gilts. However, conceptuses cultured from 2 of 5 Day-12 MS gilts secreted a major basic protein which was not evident in other co nceptus cultures until Day 14. Similarly, antiviral activity was detec ted in some cultures of Day-13 MS conceptuses, but was absent from all Day-15 LWxL conceptus cultures. The results also revealed a positive relationship between ovulation rate and the incorporation of radiolabe l into endometrial secretory proteins, which was independent of breed.