Protection of fatty acids against ruminal biohydrogenation in cattle

The increased need for intestinal absorption of unsaturated fatty acids in cattle is driven mainly by nutritional guidelines that promote reduced intake of saturated fatty acids by humans, and by reports of enhanced animal performance (such as reproductive performance) when additional essential fatty acids are supplied. A duodenal flow dataset was compiled from 25 published studies that provided up to 93 observations on fatty acid intakes and ruminal outflows across a multitude of unprotected and protected fat sources. Control diets with no added fat and diets containing unprotected fat sources had similar and predictable ruminal losses of unsaturated fatty acids (86% for linolenic and oleic acids, and 82% for linoleic acids). Rumen protection technologies that have emerged over the years involve either encapsulation of unsaturated fatty acids inside a microbial‐resistant shell (such as formaldehyde‐treated or lipid encapsulated), or alteration of fatty acid structure (such as calcium salts or fatty amides) to resist action of microbial enzymes. Calcium salts of fatty acids, because they are available commercially, comprised the majority of observations in the duodenal flow dataset. Meta‐analysis of the duodenal dataset that included random study effects revealed only a few instances where protected fat sources gave ruminal losses of polyunsaturated fatty acids that were appreciably lower than what was seen for unprotected fats. Future challenges include enhancing protection characteristics of existing rumen‐protected fat sources, and development and commercialization of novel protection strategies.