Modifying milk fat composition of dairy cows to enhance fatty acids beneficial to human health

Abstract

There is increased consumer awareness that foods contain microcomponents that may have beneficial effects on health maintenance and disease prevention. In milk fat these functional food components include EPA, DHA, and CLA. The opportunity to enhance the content of these FA in milk has improved as a result of recent advances that have better defined the interrelationships between rumen fermentation, lipid metabolism, and milk fat synthesis. Dietary lipids undergo extensive hydrolysis and biohydrogenation in the rumen. Milk fat is predominantly TG, and de novo FA synthesis and the uptake of circulating FA contribute nearly equal amounts (molar basis) to the FA in milk fat. Transfer of dietary EPA and DHA to milk fat is very low (<4%); this is, to a large extent, related to their extensive biohydrogenation in the rumen, and also partly due to the fact that they are not transported in the plasma lipid fractions that serve as major mammary sources of FA uptake (TG and nonesterified FA). Milk contains over 20 isomers of CLA but the predominant one is cis-9,trans-11 (75-90% of total CLA). Biomedical studies with animal models have shown that this isomer has anticarcinogenic and anti-atherogenic activities. cis-9,trans-11-CLA is produced as an intermediate in the rumen biohydrogenation of linoleic acid but not of linolenic acid. However, it is only a transient intermediate, and the major source of milk fat CLA is from endogenous synthesis. Vaccenic acid, produced as a rumen biohydrogenation intermediate from both linoleic acid and linolenic acid, is the substrate, and delta9-desaturase in the mammary gland and other tissues catalyzes the reaction. Diet can markedly affect milk fat CLA content, and there are also substantial differences among individual cows. Thus, strategies to enhance milk fat CLA involve increasing rumen outflow of vaccenic acid and increasing delta9-desaturase activity, and through these, several-fold increases in the content of CLA in milk fat can be routinely achieved. Overall, concentrations of CLA, and to a lesser extent EPA and DHA, can be significantly enhanced through the use of diet formulation and nutritional management of dairy cows.

Genetic variability of milk fatty acids

“…Dairy and beef products are rich sources of conjugated linoleic acid (CLA) (2.5-18.0 mg g -1 of fat in bovine milk), which is a mixture of positional and geometric isomers of C18:2 cis-9, cis-12. This structural variability explains the several functions, sometimes contradictory, attributable to CLA (Lock and Bauman 2004;Parodi 1997;Whale et al 2004). The most important isomers are the rumenic acid, C18:2 cis-9, trans-11, which represents about 75-90% of the total CLA ( 2004), and C18:2 trans-10, cis-12.…”

“…(e.g. Keating et al 2005;Lock and Bauman 2004;MacDonald 2000;Tanaka 2005;Whale et al 2004). More details can be found in many reviews about the effects of FAs on human health (e.g., Hu et al 2001;Chilliard et al 2000).…”

Supplementation with corn oil and palm kernel oil to grazing cows: ruminal fermentation, milk yield, and fatty acid profile

“…These indexes have been associated with human health (Lock and Bauman, 2004;Fontecha et al, 2009) and were reduced by more than 50%, suggesting that the inclusion of corn oil to grazing dairy cows is a valid strategy to decrease the risk of atheromas and thrombus in humans associated with milk fat intake.…”

A Review of the Metabolic Origins of Milk Fatty Acids

“…On entering the rumen, hydrolysis of the ester linkages found in TAG, phospholipids, and glycolipids is the initial transformation dietary lipids undergo (Lock and Bauman, 2004). Following this lipolysis carried out by lipases produced by rumen bacteria, NEFA are released into the rumen, adsorbed onto feed particles and hydrogenated or incorporated directly into bacterial lipids (Shingfield et al, 2008).…”