Grant: Engage Grants Program

Over the past thirty years, selective breeding in the dairy cow has resulted in substantial gains in milk yield, but an overall decrease in fertility. Cows must reproduce in order to lactate, and because more milk is produced in later lactations, it is more economically sound to keep good cows in a herd than to replace them with new animals of unknown potential. The maintenance of a pregnancy and concurrent milk production drains energy, alters stress responses, and reduces an animal's ability to mount an effective immune response, which can also impact the ability of a cow to conceive. The ability to maintain high fertility throughout an animal's natural lifespan is known as reproductive longevity (RL), and this can be improved through genetic selection. Performance Genomics Inc. (PGI), a genomics-based research company, has a line of outbred mice that has been selected for reproductive longevity (RL) that is maintained at the NSAC along with a control, Unselected line. Compared to the Unselected line, animals from the RL Selected line have 100% increase in the average numbers of litters (an average of 10 as compared to 5), without any effect on the animal's health or lifespan. Using microarray analysis, we have the ability to investigate the expression levels of all genes in the mouse genome. Determining gene expression patterns will contribute to the understanding of the mechanisms of reproductive longevity in our colony. We will also identify SNPs with functional significance, and these markers will initially be used to refine the genomic test to predict reproductive persistency that PGI is developing for the dairy industry. Using this tool, dairy herd managers will be able to improve their herds by selecting the cows with the greatest RL and increase profits through maximized milk production and herd life.