Protection of conjugated linoleic acids from ruminal hydrogenation and their incorporation into milk fat

In vitro incubations were used to assess the hydrogenation of conjugated linoleic acid (CLA) isomers 9-cis 11-trans and 10-trans 12-cis present in synthetically produced CLA-60. About 80–90% of the unprotected CLA was hydrogenated when incubated at 38°C for 24 h anaerobically with sheep rumen fluid, the main end product of hydrogenation being trans-octadecaenoic acid (C18:1). Encapsulation of the CLA in a matrix of protein provided a protection of about 70% with a 30% hydrogenation of the CLA isomers, resulting in no significant change in the trans-C18:1 but an increase in the level of stearic acid (C18:0). g sheep with unprotected CLA or protected CLA increased the proportion of isomers 9-cis 11-trans and 10-trans 12-cis in abomasal digesta. The concentration of the CLA isomers leaving the abomasum and available for absorption at the small intestine was about 3.5–4% higher for the protected CLA, confirming protection imparted by encapsulation. g lactating goats with protected CLA increased the proportion of isomers 9-cis 11-trans and 10-trans 12-cis in milk fat. The total CLA levels were enhanced by about 10-fold above the control levels present in milk fat with an efficiency of transfer into milk fat of 36–41% and 21–30%, respectively, for the two isomers.