NE1227: Ovarian Influences on Reproductive Success in Ruminants
Statement of Issues and Justification
The need as indicated by stakeholders:Impaired reproductive performance is a major cause of reduced productivity for ruminants and of reduced profitability for dairy and meat animal producers. The focus of the NE-1027 Regional Project (and its predecessor, the NE-1007, NE-161 Regional Project) has been to address nutritional, management, and environmental factors that impact ovarian activity and subsequent pregnancy rates in domestic ruminants. Our current goal is to continue this important investigative work, focusing on inter- and intra-cellular communication mechanisms that regulate oocyte growth and maturation, corpus luteum (CL) development, maintenance and regression, and early embryonic development. Alterations in inter- and intra-cellular communication due to metabolic and/or environmental stress will also be studied.
The objectives of this proposal are consistent with the second strategic goal identified in the NIFA Strategic Plan (2007-2012), which is to "Enhance the Competitiveness and Sustainability of Rural and Farm Economies". Under objective 2.2 [Provide research, education, and extension to increase the efficiency of agricultural production and marketing systems], we will evaluate our progress using performance criteria 2.2.7 [Increase and improve the reproductive performance of animals; CSREES knowledge area 301], 2.2.8 [Enhance understanding and improve application of animal nutrition; CSREES problem area 302], and 2.2.11 [Improve understanding of fundamental animal physiological processes; CSREES problem area 305]. Moreover, at a recent workshop, a group of more than 75 stakeholder scientists from federal, public, and private institutions across the United States recommended the following high impact areas as funding priorities for USDA/CSREES: development of the oocyte, follicle recruitment and development, identifying genes involved in gamete quality and embryo development, uterine-conceptus interactions with emphasis on embryonic and fetal survival, reproductive immunology, and gonadal development (Mirando and Hamernik, 2006). Our stakeholders include animal producers, the scientific community, and citizens of the region and the nation.
Importance of work and consequences if it is not done:
Improving fertility in ruminants requires fundamental knowledge about the influence of oocyte quality, follicular development, corpus luteum function, and oviduct and uterine environment on embryonic survival. The determination of ovarian and embryonic attributes of fertility in ruminants is critical to identify the underlying causes of anovulation, fertilization failure, luteal insufficiency, and early embryonic loss. Further experimental manipulation of these identified attributes will lead to a prioritization of future studies and management strategies. By enhancing basic knowledge of the underlying biology surrounding ovarian function and embryonic survival, new strategies can be developed for application by producers and veterinarians. Application of management strategies that are not based upon drug-development or use of new drugs is economical, user and consumer friendly, and preserves food quality and safety.
The technical feasibility of the work:
NE-1027 has historically been one of the most productive and cohesive multistate research groups nationwide. This is exemplified by large-scale collaborative projects that have been conducted and published by the group as a whole and thereby serves as a model for animal multistate projects [2, 3]. The technical members of NE-1027 (molecular biologists, cell physiologists, and animal scientists) are a diverse group of scientists with broad and complementary expertise in reproductive physiology of domestic ruminants. Furthermore, they have an established record of using the multistate, collaborative approach to accomplish project objectives. In the four previous years of this project, the twelve technical members of NE-1027 published over 80 refereed research papers, abstracts, theses, book chapters, and technical/extension publications. Accomplishments include: demonstrated interactions between immune and luteal cells which are important for luteal function; identified a novel shift in association of anti-inflammatory to pro-inflammatory cytokines with luteal cells during the luteal life span; established the existence of 4 endothelial cell subtypes within the CL and a method for purifying these cells in order to define functional importance of each subtype; determined a role for the endothelin receptor during luteolysis; defined the transcriptional profile of luteal cells; elucidated molecule(s) responsible for the initiation of Ca2+ oscillations during fertilization; demonstrated that moderately larger, not small preovulatory follicles and greater plasma estradiol concentrations on the day of AI increased the likelihood of subsequent pregnancy in cattle; determined that circulating progesterone concentrations are predictive of AI success; established a relationship between (1) metabolic rate and (2) luteal function, oocyte mRNA abundance, follicular steroidogenesis, and/or fertility; identified bovine miRNAs essential for successful folliculogenesis, luteal function, and early embryonic development; and demonstrated cellular and molecular actions of AMH signaling on bovine granulosa cell differentiation and predicted its role in regulating ovulation rate in a monovular species.
The advantages for doing the work as a multistate effort:
Advantages of performing this work as a multistate effort include overlapping approaches with collaborative efforts and technologies that can be directed toward several objectives simultaneously, and shared experience and data analyses that make interactions more beneficial. For example, members at different stations have contributed to unified animal and cell culture protocols and exchange samples to take advantage of unique validated procedures and will continue to do so in this project. Moreover, the combination of basic biological research and innovative applied research more effectively supports outreach programs and engagement, the goal of which is to improve reproductive performance in livestock more rapidly.
Likely impacts from successfully completing the work:
Fulfilling the objectives of this project will provide important new information concerning declining fertility among ruminants in the face of continuous improvement in production capability. Impacts include improved understanding of how oocyte quality, follicular/luteal function, and metabolic demands of production may alter key hormonal or cellular signals necessary for oocyte competence, fertilization, and embryo survival in early pregnancy. Preventive or therapeutic approaches to treat infertility and embryonic loss will benefit consultants (Nutritionists, Veterinarians, Educators, etc) and most importantly animal producers. Improved animal reproductive performance benefits the on-farm economy and sustains an agricultural production system that is highly competitive in the global economy.
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