Feeding Fats to Ruminant Animals: Issues and Opportunities

摘要

Most fats used as ingredients in cattle diets consist of triglycerides because of theirhigher fatty acid and energy concentrations. Fats refer to triglycerides that are solid atroom temperature and oils refer to triglycerides that are liquid at room temperature. Theenergy value of a fat or oil supplement is determined primarily by its fatty acid content (gtotal fatty acids/kg supplement) and very little by its fatty acid composition (g fattyacid/100 g total fatty acids). Forages stored as hay or silage generally contain 10 to 30g fatty acid/kg DM. Some species of immature pasture can contain 60 to 100 g fattyacids/kg DM, but fatty acid and linolenic acid concentrations decline appreciably as theplant matures. Most of the unsaturated fatty acid consumed by cattle is lost in the rumenthrough biohydrogenation. Because of biohydrogenation, duodenal flow of linoleic andlinolenic acids average 38 and 5 g/day, respectively. These background levels ofessential fatty acids may not be enough to meet all tissue needs, and reproductiveperformance is often improved when additional essential fatty acid is supplied.Biohydrogenation in the rumen also leads to the formation of CLA, of which someisomers can cause milk fat depression. Thus, feeding fat supplements to cattle must belimited to prevent a major shift in microbial populations in the rumen that produce theCLA isomers causing milk fat depression.