Assessing the biological effectiveness of protected lipid supplements for ruminants

Techniques are described for assessing the effectiveness with which lipids may be protected against ruminal degradation. A simple in vitro test was developed using pancreatic lipase, and this test may have application in quality control of the commercial production of protected lipid supplements, as it is applicable to supplements containing polyunsaturated or saturated lipids. All the in vitro tests overestimate the actual in vivo biological effectiveness, and this is probably due to mastication and greater microbial activity in vivo than in vitro. The poor biological response of some protected lipid supplements is most probably due to the incomplete entrapment of lipid droplets in the protein matrix.