Short-term fasting during the luteal phase of the estrous cycle perturbs circulating concentrations of progesterone and estradiol, causing a delay in the onset of the surge release of LH. Although ovulation rate is not affected by fasting in this model, number of lambs born is decreased. Fasting may affect fertility by decreasing ova quality and/or altering the oviduct/uterine environment. The objective of this study was to elucidate differences in gene expression in the oviduct near the time of expected ovulation. Estrous cycles were synchronized with PGF2α. Control ewes were given ad libitum access to good-quality grass hay throughout the experiment. Ewes in the fasted group were withheld from feed on d 7 through d 11 of the estrous cycle (d 0 = first day of estrus). On d 12 all ewes were treated with 10 mg PGF2α, and fasted ewes were returned to ad libitum feed. Oviduct tissue was collected from fasted and fed ewes during the expected peri-ovulatory period (72 hr following PGF2α and realimentation). At 72 hr, ewes were euthanized and mid sections of oviduct were dissected and snap-frozen for RNA analysis. Purified RNA was screened using the Affymetrix bovine gene chip containing ~24,000 genes at the Montana State University Functional Genomics facility. Although the RNA was ovine in origin, there is at least an 80% presence/identity when screening bovine chips with ovine RNA. Genes differentially expressed on the microarray chip were analyzed using DAVID (NIAID, NIH) for functional annotation and identification of expression patterns, and genes of interest were confirmed using semi-quantitative real time RT-PCR. Differential gene expression was observed in oviducts of the fasted ewes compared to control ewes. Affected intracellular processes include ADP ribosylation, transcription, transport, phosphorylation, ubiquitinylation, apoptosis, proteasomal degradation, GTP binding, signal transduction, carbohydrate transport and metabolism, regulation of transcription, and cell adhesion. Some genes found to be up-regulated in the oviducts of fasted ewes by microarray analysis include ARF-1, ARF-3, RhoGDP inhibitor, ataxin, aquaporin, ubiquitin, proteasomal subunit 8, HSD17B1, and a wide array of zinc finger proteins (P< 0.05). Genes down regulated by microarray analysis include, but are not limited to, TNFα, MX1, MDA5, and IRF 7 (P< 0.05). The mRNA for ARF-3 was one of several transcripts found to be up regulated by real time PCR (P< 0.01) while oxytocin receptor was found to be down- regulated (P< 0.05). These results imply a role for nutrition in molecular mechanisms regulating the environment of the oocyte at the site of fertilization which may impact overall fertility. Future studies will involve similar genetic analyses of the endometrium as well as the follicle and the study of genes/gene products which may alter the outcome of reproductive efficiency in farm animal species.