Abstract
The objective of this study was to compare the effect of contrasting sources of dietary n-6 and n-3 PUFA on expression of genes related to lipid metabolism in dairy cows. During 63 days, fifteen lactating cows were assigned to a control or basal diet containing no added lipid (n = 5 cows); and treatment diets supplemented with SO (n = 5 cows; unrefined soybean oil; 2.9% of DM) or FO (n = 5 cows; fish oil manufactured from salmon oil; 2.9% of DM). Plasma for fatty acid (FA) analysis and milk somatic cells (MSC) were obtained from all cows at the beginning of the study (day 0) and on days 21, 42 and 63. Plasma was used to determine FA transport dynamics. Compared with control and FO, plasma from SO had increased contents of C18:1 cis-9, C18:1 trans-11, C18:2 cis-9, trans-11 and total monounsaturated FA. On the other hand, compared with control and SO, FO increased plasma contents of C20:3 n-3, C20:3 n-6, C20:4 n-6, C20:5 n-3, C22:6 n-3 and total polyunsaturated FA. Moreover, plasma C18:3 n-3 and C20:5 n-3 increased over time for all diets. Compared with control, SO downregulated ACACA, INSIG1, and DGAT1, whereas FO downregulated ACACA, PPARGC1, LPIN1 and FABP3 on day 63, in MSC. At different time-points, SO and FO downregulated genes related to synthesis and intracellular transport of FA, synthesis of triglycerides, and transcription factors.
Highlights
The objective of this study was to compare the effect of contrasting sources of dietary n-6 and n-3 Polyunsaturated fatty acids (PUFA) on expression of genes related to lipid metabolism in dairy cows
Those alterations were observed in different biological functions, such as FA synthesis (ACACA), acetate and FA activation and intra-cellular transport (FABP3, FABP4), lipid droplet formation (PLIN2), and transcription regulation (THRSP), and this was observed over a period of 63 days of lipid supplementation with either palm oil or olive oil
Saturated fatty acids in milk fat were decreased with soybean oil (SO) and fish oil (FO) compared with control
Summary
The objective of this study was to compare the effect of contrasting sources of dietary n-6 and n-3 PUFA on expression of genes related to lipid metabolism in dairy cows. Polyunsaturated fatty acids (PUFA) have been used in dairy cow diets to increase unsaturated fatty acids (FA) such as C18:1 cis-9, C18:1 trans-11, and C18:2 cis-9, trans-11 in dairy p roducts[1,2] Sources for these FA can be oils of vegetable (e.g., olive, soybean) and marine (e.g., salmon oil) origin. We know[6] that there are differential effects when comparing dietary saturated FA (i.e., hydrogenated vegetable oil) with unsaturated FA sources (i.e., olive oil) It remains unclear if dietary PUFA from different sources will exert differential expression on genes related to lipid metabolism at mammary gland level over a relatively long-term lipid supplementation. MSC are representative sources of RNA in mammary gland tissue[9], and they have been successfully used in previous experiments focused on mammary gland transcriptome[6,10,11]
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