Acido Linolenico

Livestock Production Science 70 (2001) 31–48
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Review

Effect of different types of forages, animal fat or marine oils in
cow’s diet on milk fat secretion and composition, especially
conjugated linoleic acid (CLA) and polyunsaturated fatty acids
Yves Chilliard*, Anne Ferlay, Michel Doreau
`
Herbivore Research Unit, INRA Theix, 63122Saint-Genes-Champanelle, France

Abstract
This review summarises the known effects of forages, animal fats or marine oils on bovine milk fat secretion and
composition. Special attention is given to fatty acids that could play a positive role for human health, such as butyric acid,
oleic acid, C18 to C22 polyunsaturated fatty acids and conjugated linoleic acid (CLA). The efficiency of the transfer of n-3polyunsaturated fatty acids from diet to milk is reviewed. Milk fat from pasture fed cows seems to be higher in linolenic acid
than milk fat from cows receiving preserved grass or maize, but the magnitude of this difference is limited. Indirect
comparisons show that milk fat from maize silage diets is richer in short-chain FA and linoleic acid when compared to grass
silage diets. Compared tofresh grass, grass silage favours myristic and palmitic acids at the expense of mono- and
polyunsaturated FA, including CLA. Protected tallow allows for a large increase in milk fat yield, and in the percentage of
milk stearic and oleic acids, at the expense of medium chain FA. Non-protected tallow has a similar effect on medium chain
FA without increasing so much C18 FA yield, which explainsthat it does not increase milk fat yield. Dose–response curves
of milk CLA are reviewed for marine oil supplements, as well as the relationship between milk CLA and trans-C18:1
contents. The potential of marine oil supplementation to increase the mean CLA content in cow milk fat is large (more than
300% above basal values). A specific role for dietary C20:5 n-3 in the sharp decrease in milk fatsecretion after fish oil
supplementation is suggested. However, there is a need to evaluate how the different feeding strategies could change the
other aspects of milk fat quality, such as taste, oxidative stability or manufacturing value. © 2001 Elsevier Science B.V. All
rights reserved.
Keywords: Ruminant; Nutrition; Milk; Polyunsaturated n-3 fatty acids; Conjugated linoleic acid

1.Introduction
Milk fatty acid (FA) composition has a number of
effects on milk quality, including its physical (e.g.
melting point and hardness of butter, crystallisation
* Corresponding author. Tel.: 1 33-473-624-114; fax: 1 33473-624-519.
E-mail address: yves.chilliard@clermont.inra.fr (Y. Chilliard).

and fractionation of milk fat) as well as its nutritional properties (e.g. potential effectsof specific FA on
human health). FA composition also affects the
organoleptic properties of milk, due to factors such
as the effect of free short-chain FA and oxidative
changes in FA. In this review, particular emphasis is
placed on FA having a potential antiatherogenic,
antiobesity or anticarcinogenic role, such as butyric
acid, oleic acid, polyunsaturated FA (especially n-3

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Y. Chilliard et al. / Livestock Production Science 70 (2001) 31 – 48

32

FA) and conjugated linoleic acid (CLA). The FA
which have a potential negative effect on human
health, such as saturated (lauric, myristic and palmitic acids) and trans-FA, or some of them (Wolff,
´´
1995;Parodi, 1999; Sebedio et al., 1999; Williams,
2000) are also reviewed.
The metabolic pathways involved in milk fat
synthesis by the mammary gland have been reviewed
(Moore and Christie, 1981; Barber et al., 1997;
Chilliard et al., 2000; Clegg et al., this volume).
There are also several recent reviews on the ruminal
metabolism of precursors of mammary lipid synthesis, in particular on the...