Effect of Dietary Fish Oil Supplements on Levels of n-3 Polyunsaturated Fatty Acids, trans Acids and Conjugated Linoleic Acid in Ewe Milk
Massimo Mozzon1*, Natale G. Frega1, Baldassare Fronte2 and Massimo Tocchini2
1Dipartimento di Biotecnologie Agrarie ed Ambientali, Università degli Studi di Ancona, via Brecce Bianche, I-60131 Ancona, Italy
2Dipartimento di Produzioni Animali, Università degli studi di Pisa, viale delle Piagge 2, I-56100 Pisa, Italy
Article history:
Received: January 6, 2002
Accepted: June 18, 2002
Key words:
ewe milk fat, eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), fish oil, conjugated linoleic acid (CLA), trans fatty acids
Summary:
Three groups of ten lactating Sardinian ewes were used between 3rd and 6th month oflactation to determine the effects of supplementing diets with n-3 fatty acids on milk production and milk fat composition. The control group (A) was fed on a mixture of Gramineae hay with a pelleted alfalfa and concentrate; the other groups (B and C) were given the control ration supplemented with graded levels of fish oil. Milk content of nutritionally important fatty acids (n-3 polyunsaturated fatty acids, PUFA; trans acids and conjugated linoleic acid, CLA) was determined by gas chromatography. Unlike cow milk, milk of normally fed ewes contained detectable quantities of n-3 PUFA and higher amounts of CLA. The supplementation with fish oil resulted in an increased milk fat levels of n-3 PUFA, CLA and trans isomers. There was a positive correlation (R2 = 0.964) between the trans and n-3 fatty acid content in ewe milk, and a close positive correlation (R2 = 0.996) between CLA and trans monoenoic fatty acid contents. PUFA supplementation resulted in a slightly, but not statistically significative, decrease of milk fat percentage. On the contrary, dietary fish oil markedly affected milk production: ewes fed on the n-3 supplemented diet produced more milk than the ewes fed with the control diet.
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