The recent 25th Alltech International Animal Health and Nutrition Symposium provided an opportunity to demonstrate the value of nutrigenomics, the branch of molecular biology which evaluates the effects of nutrients on expression of genes, in the development of feeding strategies to enhance the performance of poultry flocks.
With this, scientists can compare alternative dietary formulations and investigate their effect on upregulating or suppressing genetic expression to achieve a beneficial metabolic outcome.
With the technique, researchers:
- feed control and experimental diets to subjects;
- harvest tissue samples, usually comprising muscle or liver
- extract RNA for assay;
- label purified RNA with a fluorescent tag and apply to an Affymetrix GeneChip microarray.
Each of the chips contains probes, numbering over 1 million, that correspond to upwards of 20,000 genes.
After allowing hybridization overnight, the chips are washed to remove non-hybridized RNA. using a special scanner, fluorescence is detected, the amount of which is proportional to the gene's activity.
Through investigation, microarray analysis was used to establish the effect of feeding selenomethionine on the genes associated with the synthesis of glutathione peroxidase. This enzyme, with co-factors such as selenium, is directly associated with the protection of cell membranes against oxidation.
Although growth weight and feed consumption were not affected by source of selenium, activity of GPxI, the gene responsible for production of the enzyme, was significantly upgraded when broilers received selenium in the organic form compared to inorganic sodium selenite.
This has implications for both immune response and resistance to stress.
Incorporating organic selenium in diets has also been shown to upregulate the genes responsible for the metabolism of polyunsaturated fatty acids and enhancing the digestibility of nitrogen.