Dietary lipids and forages interactions on cow and goat milk fatty acid composition and sensory properties

Reproduction Nutrition Development, Sep 2004

Yves Chilliard, Anne Ferlay

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Dietary lipids and forages interactions on cow and goat milk fatty acid composition and sensory properties

Reprod. Nutr. Dev. Dietary lipids and forages interactions on cow and goat milk fatty acid composition and sensory properties s CHILLIARD 0 FERLAY 0 0 INRA Unité de Recherches sur les Herbivores, Équipe Tissu Adipeux et Lipides du Lait , Theix, 63122 St-Genès-Champanelle , France - This review summarises the known effects of dietary factors on bovine and caprine milk fatty acid composition, as well as the regulation of cow and goat mammary lipid secretion. Special attention is given to fatty acids that could play a role for human health, such as saturated fatty acids, oleic acid, n-6- or n-3-C18 to C22 polyunsaturated fatty acids, trans isomers of C18:1 and C18:2, and isomers of conjugated linoleic acid (CLA). The main dietary factors taken into account are the nature of forages, including pasture, the forage:concentrate ratio and diet starch content, and the supplementation of dairy rations with crude or processed vegetable oils or oilseeds, and vitamin E. A particular emphasis is given to studies on interactions between these dietary factors, which show that there is a considerable plasticity of ruminant milk fatty acid composition. Despite the existence of several studies on the effects of dietary factors on the sensorial quality of milk and dairy products, there is a need to evaluate more deeply how the different feeding strategies could change the nutritional, sensorial and technological aspects of milk fat quality. - Review 1. INTRODUCTION Dairy products provide 25 to 35% of the overall saturated fat consumed by man, which makes them the preferential target of dieticians’ criticisms [ 1 ]. The deleterious reputation of saturated fatty acids (FA) should however be weighted with the fact that stearic acid has no atherogenic effect. The allegedly atherogenic effect of certain trans mono-unsaturated fatty acids has not been confirmed as regards the main isomer present in milk, i.e. vaccenic (trans11-18:1). The interest of increasing the n-3/n-6 ratio of polyunsaturated fatty acids (PUFA) has been confirmed. Lastly, the properties of conjugated linoleic acid (CLA), whose main isomer, rumenic acid (cis9,trans11-18:2), exhibits interesting features, as demonstrated in animal models, are now better known, for the prevention of certain forms of cancer in particular. These new facts underline the interest of modulating the milk FA composition. Mammals’ milk FA composition is linked to intrinsic (animal breed, genotype, lactation and pregnancy stages) or extrinsic (environmental) factors. In a given animal species, the effects linked to breed or genotype are significant but restricted [ 2–6 ] and they can only be achieved in the mid-term or through interaction with constraints inherent in other criteria. The lactation stage effect is marked and mainly linked to lipid 1 Number of lipid-supplemented groups (amount of lipids, g·d–1). 2 Effects expressed as “treated group-control group”, * P < 0.05. 3 From [ 20 ]. 4 Review by A. Ferlay and Y. Chilliard, unpublished. 5 Whole, rolled or ground. store mobilisation in early lactation [ 7 ], but it only lasts a few weeks each year. In contrast, seasonal effects are quantitatively very important. Although certain effects of temperature or photoperiod can be evidenced, it is the variations of ruminant nutrition which determine most of the seasonal variations of milk FA composition. The effects of cheesemaking technology on FA composition are minimal in relation to those of feeding [ 8 ]. Nutrition therefore constitutes a natural and economical way for farmers to sharply and rapidly modulate milk FA composition, in particular by adding lipid supplements to the diet. The consequences of these practices on dairy cows’ milk fat and protein synthesis and contents are now well known: a tendency to increase milk production (with saturated lipids and soybean in particular), slight but almost systematic decrease in protein contents, limited variations of the fat content except with rapeseed oil and especially with fish oil, which induce sharp decreases, and encapsulated lipids that strongly increase it (Tab. I). In contrast, nearly all types of lipid supplements induce a sharp increase in goat milk fat content without modifying milk yield or protein content [ 7 ]. After a reminder of the mammary lipogenesis metabolic pathways, this article successively analyses the impacts of dairy cows’ and goats’ diets on the main fatty acid classes: saturated and cis mono-unsaturated, polyunsaturated and lastly CLA and trans mono-unsaturated. Then the effects of nutrition on the sensory characteristics of dairy products will be briefly evoked, as they may partly be due to post-milking lipolysis of milk fat (short-chain fatty acid release) or to polyunsaturated fatty acid oxidation. 2. METABOLIC PATHWAYS NUTRIENT FLUXES INVOLVED IN MILK FAT SYNTHESIS 2.1. Mammary lipogenesis Milk fatty acids have a dual origin: they are either taken up from plasma lipoproteins (60% (...truncated)


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Yves Chilliard, Anne Ferlay. Dietary lipids and forages interactions on cow and goat milk fatty acid composition and sensory properties, Reproduction Nutrition Development, 2004, pp. 467-492, Volume 44, Issue 5, DOI: doi:10.1051/rnd:2004052