Project Number: 3030-31000-017-15
Start Date: Aug 01, 2012
End Date: Apr 30, 2015
Specific aim 1 and a portion of specific aim 2 will be accomplished at Fort Keogh by ARS employees. Aim 1 will be conducted in year 1 and a portion of year 2 by repeatedly transferring in vitro produced embryos into approximately 300 heifers and determining early pregnancy success (day 45). After 6 replications of transferring embryos, measuring pregnancy success and terminating pregnancies, heifers will be classified as being Superior (> 5 successful pregnancies) or Inferior (< 2 pregnancies) recipients for use in Aims 2 and 3. In aim 2, the physiological mechanisms underlying uterine endometrial receptivity and successful pregnancy will be evaluated. Only studies 2.1 and 2.2 will be conducted at ARS. In study 2.1, serum progesterone concentration will be used to ensure variation of uterine receptivity is not limited by progesterone binding and activation of endometrial progesterone receptors. In study 2.2, the stable plasma metabolite of prostaglandin F2a (PGFM) will be evaluated to estimate the sensitivity of the uterine endometrium for maternal recognition of pregnancy signal. This is accomplished by measuring the prostaglandin response to oxytocin administration that must be blocked to support pregnancy establishment. Heifers that are more sensitive to oxytocin administration might be less likely to become pregnant because of diminished potential for the maternal recognition of pregnancy signal to be perceived. Approximately 50 Superior and 50 Inferior recipient heifers will be identified through the above studies for transport to Washington State University for further studies of differential protein expression (study 2.3) and secretion (study 2.5) by the uterine endometrium, their effects on embryo development (study 2.4), and ultimately variation within the genome of Superior and Inferior recipients as measured by SNP analyses and copy number variants (Aim 3).