Fat in moderation is an essential component of the human diet. It provides energy, fat-soluble vitamins and essential fatty acids. It also enhances palatability by providing texture and flavour to foods. In the past few decades, however, the composition of beef fat has been maligned due to its high content of saturated fat and wide spread recommendations have been made to limit red meat consumption. Recently, trans fatty acids have also been a topic of interest as more information becomes available concerning the negative health effects of these fatty acids. In this sense, new regulations being enacted in Canada require food manufacturers to disclose the total trans fat content of the products and additional regulations are in development to limit trans fat consumption. Interestingly, however, not all fatty acids containing trans double bonds are unhealthy. Both conjugated linoleic acid (CLA) and vaccenic acid (trans11-18:1) have health promoting properties and can be enriched in beef. When feeding highly fermentable diets, however, CLA and vaccenic acid can be replaced by trans10-18:1 which can have negative health implications. The goal of the proposed work will be to provide information on how to modify and control the total fatty acid profile in beef, especially trans 18:1 and CLA isomers, and how ruminal microflora can influence their production when feeding different diets. In this sense, the fatty acid profile of pasture versus concentrate-fed animals will be compared initially, and then, different feed ingredients (i.e. buffer, dried distillers’ grains) will be incorporated into a typical feedlot diet (mostly barley) to study their influence on carcass composition, meat quality and fat composition. Helping to define the levels of dried distillers’ grains that can be included in livestock diets as an economical source of both feed and polyunsaturated fatty acids (18:2n-6) will also benefit the cattle and bioethanol industries and, in general, the environment.
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