Short term changes in nutrition during the peri-conceptual period of the ewe affect total cell number in blastocyst

Abstract

Manipulation of nutrition is used widely to improve pregnancy outcome in livestock. In sheep, increased dietary intake for a relatively short time will increase the ovulation rate by increasing gonadotrophin secretion (Downing et al., 1995). However overfeeding can decrease embryo quality in both sheep and cattle, and it appears that this results from changes primarily at the level of the follicle or oocyte (Boland et al. 2001). In a recent study examining the effects of short-term nutritional manipulation around the time of ovulation and conception, we reported that acute changes in nutrition appeared to influence several parameters including the ratio of trophectoderm and inner cell mass cells in the blastocyst (Kakar et al. 2001). The current study was conducted to discriminate between changes to the embryo resulting from nutritional influences during the preovulatory or postovulatory period.