Upgrading the lipid fraction of foods of animal origin by dietary means: rumen activity and presence of trans fatty acids and CLA in milk and meat

Abstract

The recent literature dealing with the effect of the diet on the quality of milk and meat fat is reviewed. Some aspects of the rumen metabolism of lipids are dealt with: lipolysis, bio-hydrogenation, synthesis of microbial fatty acids and inhibition mechanisms on fermentation. Firstly, the influence of forage is considered. Pasture is the best forage, better if high hill pasture, as compared to hay and silage: short chain fatty acids (SCFA) (shorter than C10) are increased, medium chain fatty acids (MCFA) (C12 through C16) are decreased, oleic (OA), linoleic (LA) and linolenic (LNA) acids are increased and so are the conjugated linoleic acid pool of isomers (CLA) and n-3 polyunsaturated fatty acids (n-3 PUFA). Secondly, the energy supplementation of diets with fats is looked at. Animal fats depress milk yield and SCFA, while OA is increased because of the enhanced activity of mammary ∆ 9 desaturase. Fish oil depresses milk yield as well, but promotes CLA and n-3 PUFA. If animal fats are protected against rumen bacteria, milk yield and milk fat depression are avoided. Vegetable fats are richer in unsaturated fatty acids (UFA), thus more susceptible to the rumen bio-hydrogenation. As calcium soaps or inside whole seeds, plant fats are protected and CLA is increased. CLA is an important component of fat. In ruminants it comes from the desaturation of vaccenic acid (VA) both in rumen and udder; and the yield of VA depends on the diet quality. In conclusion, simple directions are given on how to improve the quality of animal fat by dietary means, without affecting yield.

Different level of conjugated linoleic acid (CLA) in dairy products from Italy

“…Organic yoghurt showed cis-9,trans-11 CLA average value of 6.05 mg/g fat; a large variability was observed in this products class that is probably due to cows feeding which influences the fat composition of milk. The recent literature dealing with the effect of the diet on the quality of milk fat was reviewed by Bauman et al (1999) and Antongiovanni et al (2003). Many dietary factors are known to affect CLA in milk fat; they are grouped into categories relative to the potential mechanism by which they may act.…”

Meat Quality of Lambs Fed Different Saltbush Hay (Atriplex Nummularia) Levels

“…Some studies reported a greater proportion of linolenic acid and its derivatives in the fat of grazing sheep than those fed concentrate diets, consistent with the results of this work (Woods and Fearon, 2009;Oliveira et al, 2013). Although the most studies usually find higher biohydrogenation in forage fed animals than in concentrate fed animals, another authors reports lower biohydrogenation in the rumen when the diet is composed of a higher level of forage (Antongiovanni et al, 2003;Abidi et al, 2009;Buccioni et al, 2009).…”

Changes in conjugated linoleic acid and C18:1 isomers profile during the ripening ofPecorino Toscanocheese produced with raw milk

“…The most biologically active isomer is Rumenic Acid (RA), the cis9 trans11 isomer, synthesized in ruminants partly in rumen, by isomerization of LA, and partly in the mammary gland by Δ 9 desaturation of vaccenic acid (VA) (Griinari and Bauman, 1999). Sheep milk is rich in CLA, since it has a higher fat content than that from cows or goats and because sheep feeding regimen is often based on pasture (Antongiovanni et al, 2003;Mele, 2009). The production of sheep cheese plays an important economic role in the Mediterranean area where dairy sheep is present since ancient times.…”