Apparently, most biologically active isomer of conjugated linoleic acid (CLA) is cis-9, trans-11, which is accounted for more than 80% of the isomers of CLA in milk fat (Chin et al., 1992). The cis-9, trans-11 CLA is an important component of milk fat and beneficial to human health due to its anti-carcinogenic properties. Research has therefore focused on methods of altering CLA content of milk fat. In corporation of commercial sources of CLA into dairy cattle rations is one potential means of increasing CLA content of milk