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Lipids

Title:		"t10,c12-18:2-induced milk fat depression is less pronounced in cows fed high-concentrate diets"
Author(s):		Glasser F; Ferlay A; Doreau M; Loor JJ; Chilliard Y;
Address:		"INRA, UR1213 Herbivores, Site de Theix, 63122, Saint-Genes-Champanelle, France"
Journal Title:		Lipids
Year:		2010
Volume:		20100828
Issue:		9
Page Number:		877 - 887
DOI:		10.1007/s11745-010-3460-x
ISSN/ISBN:		1558-9307 (Electronic) 0024-4201 (Linking)
Abstract:		"In intensively reared dairy cows, milk fat secretion is reduced in response to high-concentrate diets and it is often referred to as the 'milk fat depression' (MFD) syndrome. Some trans fatty acid (FA) isomers produced in the rumen of the cows, including t10,c12-18:2, are known for their inhibitory effect on mammary lipogenesis. To study whether this effect depends on the basal diet, duodenal infusions of t10,c12-18:2 were performed on cows fed four different diets (a factorial arrangement of forage:concentrate ratio and linseed oil supplementation). The overall response obtained with t10,c12-18:2 infusion was consistent with previous studies: a decrease in milk fat content and yield without significant variations in milk yield. Mean transfer efficiency of infused t10,c12-18:2 was 19.6%. However, the decrease in milk fat and FA yields (both de novo synthesis and preformed long-chain FA) was less pronounced in cows fed high-concentrate diets (-27% of the initial level), compared with cows fed low-concentrate diets (-42% of initial level). This difference was independent of dietary oil supplementation and milk FA yield before infusion. Results pertaining to effects of dietary forage:concentrate ratio were confirmed by statistical meta-analysis of data from previously published t10,c12-18:2 infusion experiments. This study shows that in cows fed MFD diets the mammary gland becomes more resistant to or experiences a lower response potential to further inhibition of lipogenesis and/or delta-9 desaturation of FA"
Keywords:		"*Animal Feed Animals Cattle Fatty Acids/*analysis Linoleic Acids, Conjugated/administration & dosage/*pharmacology Linseed Oil/administration & dosage Milk/*chemistry;"
Notes:		"MedlineGlasser, Frederic Ferlay, Anne Doreau, Michel Loor, Juan J Chilliard, Yves eng 2010/08/31 Lipids. 2010 Sep; 45(9):877-87. doi: 10.1007/s11745-010-3460-x. Epub 2010 Aug 28"