State of the art in rumen lipid protection technologies and emerging interfacial protein cross-linking methods

Polyunsaturated fatty acids given to ruminants are to a large extent hydrogenated to more saturated forms by microbial metabolism. Numerous protection technologies have been developed to overcome this hydrogenation process in order to increase the amount of unsaturated fatty acids bypassing the rumen and resulting in an effective transfer to the peripheral tissues. This review gives an overview of the current state of the art in rumen lipid bypass technologies, with the focus on both patent-described protection mechanisms, possible advantages or drawbacks of the technologies, and protection results being described in recent scientific literature. Lipid bypass techniques which are dealt with include calcium salts, fatty acyl amides, aldehyde treatment, non-enzymatic browning, lipid composite gels, and encapsulation within lipids. Further, the potential of a novel rumen lipid protection technology, based on interfacial cross-linking of emulsions, is explored. Therefore, an overview is given on current knowledge of different types of enzymatically induced cross-linking of protein at emulsion interfaces, both for existing food and possible ruminal bypass applications. Practical applications: Both from a human and animal health care as well as from a resource-saving and economic perspective, protection of PUFA from ruminal BH is of interest. Protection, release, and absorption principle of a lipophilic rumen bypass product: As polyunsaturated fatty acids (P) are hydrogenated to more saturated fatty acids (S) upon ruminal passage (panel A), P sources administered to ruminants have to be protected against microbial turnover to transfer them to the peripheral tissues (panel B).