Mammary gene expression profile of goats receiving high or low forage diets supplemented or not with lipids

Animal nutrition considerably affects milk composition that influences its nutritional quality. Milk component synthesis and secretion by the mammary gland involve the expression of a large number of genes whose nutritional regulation remains poorly defined. In this study, 16 lactating goats received 4 experimental diets differing in either forage to concentrate ratio (high forage, HF, or low forage, LF) supplemented, or not, with lipids (whole rapeseeds, RS, or sunflower oil, SO) in a 4 x 4 Latin Square design. To investigate the pathways regulated by nutrition, we examined the effect of these diets on the expression of approximately 8400 genes in caprine mammary gland using a bovine oligonucleotide microarray. Due to the limited quantity of mammary RNA available, equal amounts of total RNA sample from mammary gland of each goat belonging to the same Latin Square group were mixed together before labeling. Each mammary pooled sample (4 by dietary treatment) was then co-hybridized with a standard reference corresponding to a mixture of purified total RNA from several caprine tissues. Each hybridization was repeated in a dye-swap manner for a total of 32 slides (8 slides and 4 independent comparisons by dietary treatment).