Submitted to: Progressive Cattlemen
Publication Type: Trade Journal
Publication Acceptance Date: 1/11/2016
Publication Date: 2/1/2016
Citation: Cushman, R.A. 2016. Where we've been and where we're going on heifer selection. Progressive Cattleman. February:71-73.
Technical Abstract: Selecting highly productive replacement heifers is an important component of economic efficiency for a cow-calf producer. If we can select replacement heifers early, we can implement development strategies to improve their reproductive efficiency. Genomics becomes a powerful tool both for selecting and developing replacement heifers. From a selection perspective, we seek to identify genetic markers that associate with 1) the ability to conceive early as a heifer and 2) reproductive longevity, because conceiving early is associated with a longer productive life (P < 0.01). We must remember, however, that a gene is more than just a sequence; it is code for a protein that has biological function and through nutritional programming, we can increase or decrease the amount of protein that gene produces. Decreasing caloric intake in peri-pubertal heifers increases the number of primordial follicles in the bovine ovary (P < 0.05) and increases the transcript abundance of SLIT2 in the bovine ovary (P < 0.05). Proposed actions of SLIT2 in the ovary are to increase follicle formation and development. From this we can conclude that nutritional programming of the bovine ovary has changed the function of the transcriptional machinery of the SLIT2 gene (i.e. epigenetic modification), leading to a change in phenotype. Because the number of follicles in the the mammalian ovary is related positively to reproductive longevity, we can see where both molecular genetics and functional genomics can contribute to our ability to select and develop highly productive replacement heifers.