Effects of fish oil and additional starch on tissue fatty acid profile and lipogenic gene mRNA abundance in lactating goats fed a diet containing sunflower-seed oil

In dairy cattle, diet supplementation with oils affects the lipid metabolism in body tissues via changes in the partitioning and deposition of fatty acids (FAs) and lipogenic gene expression; however, limited data are available in goats. Eight Alpine goats were fed a grassland hay diet supplemented with 90 g/day of sunflower-seed oil or 90 g/day of sunflower-seed oil and fish oil (2 : 1) plus additional starch. The goats were slaughtered on day 21 of the treatments and samples of the mammary secretory tissue, liver, omental and perirenal adipose tissues (ATs) were collected to characterise their FA composition and the mRNA abundance of lipogenic genes and transcription factors involved in their regulation, and to examine the impact of the diet composition on the same parameters. The results are in agreement with the specific physiological adaptation in the lipid metabolism of body tissues that is likely to occur during late lactation because of the coexistence of an active lipogenesis in the mammary secretory tissue and a significant anabolic activity in the ATs. These latter tissues were characterised by high concentrations of saturated FA and very low polyunsaturated FA (PUFA) levels. The content of PUFA was relatively higher in the mammary secretory tissue, in particular in the case of polyunsaturated C18. The highest PUFA contents were found in the liver, in accordance with the greater mRNA abundances of the genes that encode the necessary enzymes for very long-chain n-3 and n-6 PUFA synthesis. However, substantial differences between n-3 and n-6 pathways would most likely exist in the goat liver. Overall, differences in diet composition induced limited changes in the mRNA abundance of genes involved in lipid metabolism, and these were not associated with the few variations observed in tissue FA composition.