Project Number: 5364-31000-007-08
Project Type: Nonfunded Cooperative Agreement

Start Date: Mar 01, 2006
End Date: Oct 31, 2010

Objective:
Embryonal and fetal mortality are a significant source of economic loss in the livestock industry. The objective for this cooperative research is to determine whether ovulation of follicles of different ages, or from different follicular waves, alters oocyte competence and rates of embryonal and fetal loss in sheep. This research will also be used to determine whether circulating progesterone and estradiol concentrations may be used to predict oocyte competence and rates of embryonal and fetal loss in sheep. Results may permit researchers to define a critical stage of development when follicles transition from ¿young¿ to ¿old¿ and when oocytes are likely to lose their ability to develop into embryos or fetuses that will survive to term. The results of the research are expected to provide the basis for reproductive management strategies that will improve embryonal and fetal survival to term and increase the reproductive potential of sheep.

Approach:
Experiments will be conducted to determine whether ovulation of follicles, and thus the oocytes produced, from penultimate (i.e., old follicles and oocytes) and/or ultimate (i.e., young follicles and oocytes) follicular waves affects fertility and prolificacy of ewes. Prolificacy is an integrated measure of ovulation rate, fertilization rate, and embryonal and fetal survival to term. The experiments will be designed to take advantage of an experimental model that creates ovulations from penultimate and ultimate follicular waves. Specifically the model will be used to: 1) Compare conception rates, embryonal mortality, and prolificacy in ewes ovulating follicles from only the ultimate wave (young) with those variables in ewes ovulating follicles from the penultimate and ultimate waves (old and young), 2) Measure patterns of progesterone and estradiol in peripheral blood of sheep with different progesterone concentrations so that ewes can be categorized into low and high progesterone groups (and low and high estradiol groups) and to determine whether age or competence of the ovulatory follicle(s) are related to concentrations of these hormones, 3) Determine whether follicular wave source (penultimate vs. ultimate), determined from retrospective mapping of follicle growth, regardless of specific follicular age, affects oocyte competence and embryonal and fetal mortality. Documents NFCA with W. VA. U.