Project Number: 5434-31000-014-00
Project Type: Appropriated

Start Date: Jul 31, 2002
End Date: Jul 30, 2007

Objective:
1) Determine the role of follicular growth in maintaining pregnancy during early gestation. 2) Determine genetic and environmental partitioning of phenotypic variation in reproductive traits of heifers and bulls measured early in life under two differing planes of nutrition and evaluate their relationships with lifetime reproductive performance of cows. 3) Identify quantitative trait loci and novel genes affecting attainment of puberty, probability of conception, return to estrus after calving, reproductive longevity, and other components of sustained reproduction. 4) Develop selection indexes to increase genetic potential for profitability of beef production through optimal use of feed inputs in sustainable cow-calf production.

Approach:
A stabilized composite population, composed of 50% Red Angus, 25% Charolais, and 25% Tarentaise germplasm, will be used to fulfill all objectives. Two plans of nutrition will be imposed on cows during winter and on their progeny during post-weaning development. Obj. 1: Follicular development will be monitored by ultrasonography. Maintenance of pregnancy will be assessed from serum progesterone concentration in blood samples collected on d 14, 20, 27, 40,54,and 68 post-insemination. Effect of ovulatory follicle size on pregnancy rate will be determined by logistic regression. Obj. 2: Historical data will be analyzed using mixed model methods to determine breeding values for longevity. Traits of progenies developed under the two nutritional environments and measured early in life will be correlated with genetic differences in longevity. Obj. 3: Two approaches will be used: the first is a genome-wide scan for quantitative trait loci affecting reproductive traits and longevity; and the second is gene expression profiling using microarrays to identify novel genes associated with reproductive performance. Initial microarray experiments will focus on postpartum anestrus versus cycling cows. Obj. 4: Selection index, with relative economic values derived by simulation, will be used to develop selection criteria for sustainable cow-calf production.

Project Team

Macneil, Michael Alexander, Leeson Geary, Thomas Grings, Elaine Roberts, Andrew - Andy

Project Annual Reports

FY 2003

Related National Programs

Food Animal Production (101)

Related Projects

Enhanced Sustainability of Rangeland Agriculture Through Increased Animal Productivity    Beef Cattle Improvement Through Genetic Prediction Technology