Regulacion nutricional de la expresion de los genes implicados en la lipogenesis en ovejas alimentadas con aceite de girasol. 1. Tejido secretor mamario

International audience; A study was conducted in ewes consuming sunflower oil to investigate the response of the mammary secretory tissue, in terms of mRNA abundance of genes involved in lipogenesis, to a diet known to induce changes in milk fatty acid (FA) composition. Ten sheep (5 animals/treatment) received a total mixed ration based on alfalfa hay and a concentrate (F:C 60:40), supplemented with 0 (Control) or 25 (Gi) g of sunflower oil/kg dry matter, for 7 weeks. At the end of the experiment, milk production and composition was recorded and analysed (day 48) and the ewes were euthanized (day 49) for sampling of mammary secretory tissue to examine the nutritional regulation of mammary lipogenesis, using a candidate gene approach. The inclusion of Gi in the diet modified milk FA composition and secretion, decreasing the percentages of FA derived from de novo synthesis and increasing that of long-chain FA. However, results of mammary mRNA abundance of genes involved in lipid metabolism ( ACACA, FASN, LPL, CD36, FABP3, SCD1, S CD5, SREBF1 and PPARG) suggest that transcriptional regulation is not directly involved in these changes, at least when this is measured after a long period on the feeding treatments.