Dietary linseed oil with or without malate increases conjugated linoleic acid and oleic acid in milk fat and lipoprotein lipase and stearoyl-coenzyme A desaturase gene expression in mammary gland and milk somatic cells of lactating goats
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چکیده
Supplementary dietary plant oils have the potential to alter milk fatty acid composition in ruminants as a result of changes in the amount and kind of fatty acid precursors. We hypothesized that linseed oil in combination with malate (a key propionate precursor in the rumen) would increase ∆9 unsaturated fatty acids and specific gene expression in somatic cells and mammary glands of lactating goats. Twelve lactating goats were used in a 3 × 3 Latin square design. Treatments included the basal diet (CON), the CON plus 4% linseed oil (LO), and the CON plus 4% linseed oil and 2% dl-malate (LOM). Relative to CON, the LO and LOM supplements increased the daily intake of palmitic (16:0), stearic (18:0), oleic (18:1n-9), linoleic (18:2n-6), α-linolenic (18:3n-3), and γ-linolenic acids (18:2n-6); α-linolenic acid intake was increased over 9-fold, from 6.77 to over 51 g/d (P < 0.02). The LO and LOM supplements increased daily milk yield, milk fat yield, and milk fat percentage (P < 0.05). The LOM supplement also increased milk lactose percentage and daily yield (P = 0.03). Both the LO and LOM supplements increased plasma glucose and total cholesterol and decreased plasma β-hydroxbutyrate concentrations (P = 0.03). The LO and LOM supplements increased concentrations of stearic acid; trans-vaccenic acid (TVA; 18:1trans-11); cis-9, trans-11 CLA; trans-10 cis-12 CLA; and α-linolenic acid in rumen fluid and increased the concentrations of oleic acid; TVA; cis-9, trans-11 CLA; trans-10, cis-12 CLA; and α-linolenic acid in plasma lipids and milk fat (P < 0.05). Conversely, the LO and LOM supplements decreased shortand medium-chain SFA, including lauric (12:0), myristic (14:0), and palmitic acids, in plasma and milk fat (P < 0.05). Relative mRNA levels for lipoprotein lipase and stearoyl-CoA desaturase (SCD) gene expression were increased in somatic cells and mammary gland tissue by LO and LOM (P < 0.05). We conclude that the higher intake and ruminal production of stearic acid promoted SCD gene expression in somatic cells and mammary tissue. Furthermore, milk somatic cells are a suitable substitute for documenting treatment effects of dietary oils on gene expression in goat mammary tissue.
منابع مشابه
Conjugated linoleic acid-induced milk fat reduction associated with depressed expression of lipogenic genes in lactating Holstein mammary glands.
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