title: Effects of pasture versus confinement and marine oil supplementation on the expression of genes involved in lipid metabolism in mammary, liver, and adipose tissues of lactating dairy cows.
abstract: Research was conducted to evaluate the effects of management system (MS), marine lipid supplementation (LS), and their interaction on the relative mRNA abundance of 11 genes involved in lipid synthesis in mammary, liver, and subcutaneous adipose tissues in lactating dairy cows. These genes included those involved in FA uptake (LPL), de novo FA synthesis (ACACA, FASN), FA desaturation (SCD1, FADS1, FADS2), and transcriptional regulation of lipogenesis (SREBF1, SCAP, INSIG1, THRSP, and PPARG). Forty-eight peripartal Holstein cows were blocked by parity and predicted calving date and assigned to either a pasture (n=23) or confinement (n=25) system. Within each system, cows were allocated randomly (7-9 cows per treatment) to a control (no oil supplement) or 1 of 2 isolipidic (200 g/d) supplements, fish oil (FO) or microalgae (MA), for 125 ± 5 d starting 30 d precalving. The experiment was conducted as a split-plot design, with MS being the whole plot treatment and LS as the subplot treatment. At 100 ± 2 DIM, 4 cows from each treatment combination (24 cows in total) were euthanized and tissue samples were collected for gene expression analysis. No interactions between MS and LS were observed regarding any of the variables measured in this study. Milk production (34.0 vs. 40.1 kg/d), milk fat (1.10 vs. 1.41 kg/d), protein (0.95 vs. 1.22 kg/d), and lactose (1.56 vs. 1.86 kg/d) were lower for pasture compared with confinement. The effect of LS on milk production and milk composition (yields and contents) was significant only for milk fat content that was reduced with MA compared with FO (3.00 vs. 3.40%) and the control (3.56%). The mammary mRNA abundance of PPARG (-32%) and FASN (-29%) was lower in grazing compared with confined cows, which was accompanied by reduced (-43%) secretion of de novo synthesized fatty acids in milk. Grazing was associated with reduced expression of ACACA (-48%), FASN (-48%), and THRSP (-53%) in subcutaneous adipose tissues, which was consistent with the lower body condition score (i.e., lower net adipose tissue deposition) in grazing compared with confined cows. Feeding either FO or MA downregulated hepatic expression of FASN, SCD1, FADS2, and THRSP. The reduced secretion of de novo synthesized fatty acids in milk of grazing cows compared with confined cows might be related in part to the downregulation of genes involved in lipid synthesis, and that LS have tissue-specific effects on expression of genes involved in lipid metabolism, with liver being the most responsive tissue.
authors.affiliation: Department of Biology, Dalhousie University, Halifax, Nova Scotia B3H 4J1, Canada.
authors.forename: P
authors.initials: P
authors.lastname: Vahmani
authors.affiliation: Azar Agriculture, Truro, Nova Scotia B2N 5Z3, Canada. Electronic address: kglover@eastlink.ca.
authors.forename: K E
authors.initials: KE
authors.lastname: Glover
authors.affiliation: Department of Plant and Animal Sciences, Dalhousie University, Truro, Nova Scotia B2N 5E3, Canada.
authors.forename: A H
authors.initials: AH
authors.lastname: Fredeen
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism; D000821:Animal Feed / Q000032:analysis; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002417:Cattle / Q000235:genetics / Q000502:physiology*; D003612:Dairying / Q000379:methods*; D004032:Diet / Q000662:veterinary; D019587:Dietary Supplements / Q000032:analysis; D005260:Female; D005395:Fish Oils / Q000008:administration & dosage / Q000378:metabolism*; D005786:Gene Expression Regulation; D007774:Lactation; D050155:Lipogenesis; D008099:Liver / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000378:metabolism; D058086:Microalgae / Q000737:chemistry*; D009928:Organ Specificity; D011897:Random Allocation; D060888:Real-Time Polymerase Chain Reaction / Q000662:veterinary
chemical_list: D005395:Fish Oils
keywords: fish oil; grazing; microalgae; total mixed ration