Dietary sources of unsaturated fatty acids for animals and their transfer into meat, milk and eggs: A review

Abstract

Dietary intake of unsaturated fatty acids (UFA) has been shown to reduce the risk of cardiovascular disease (CVD) and possibly the incidence of some cancers, asthma and diabetes among other conditions. Meanwhile, animal products have been criticised for their high content of saturated fatty acids (SFA), being damaging to health. Modification of animal diets can now easily increase the proportion of UFA in meat, milk and eggs. Consuming a greater proportion of these beneficial fatty acids as part of an everyday diet will appeal to the public, as opposed to taking dietary supplements. This study encompasses a review of the literature on dietary sources of UFA available for animals and their subsequent transfer into milk, meat (beef, lamb, pork, poultry) and eggs. Including these fatty acid sources in the diet of animals improves the fatty acid profile of milk, meat and eggs by increasing the ratio of UFA:SFA, decreasing the ratio of n−6: n−3 fatty acids and, with ruminant products, increasing conjugated linoleic acid (CLA) levels. Care must be taken however, when introducing these fatty acid sources into animal diets as some adverse effects can result. For example, large amounts of UFA in the diet of dairy cows may affect rumen activity, reducing milk yield, fat and protein concentrations, while the impact of increased levels of polyunsaturated fatty acids (PUFA) in meat on shelf life and flavour parameters is an area that warrants further investigation. Novel fatty acid sources such as hemp, camelina or lupin, although effective in some instances, are so far proving an expensive option for commercial purposes. Current thinking on the relevance of the dietary n−6: n−3 ratio to cardiovascular risk in humans is also examined.