Effect of breed, parity and stage of lactation on milk conjugated linoleic acid content in Italian Friesian and Reggiana cows

Conjugated linoleic acid (CLA) refers to a mixture of positional and geometrical isomers of fatty acids with 18 carbon atoms and 2 conjugated double bounds. Some isomers are assumed to play an important role in human health (Pariza et al., 2001). The cis9, trans11 CLA isomer (rumenic acid; RA) is the major CLA isomer in dairy products and it origins partly (more than 70%) from mammary desaturation of trans11 C18:1 (vaccenic acid; VA) and partly from rumen biohydrogenation of linoleic acid (Corl et al., 2001). The enzyme involved in the mammary RA desaturation is stearoyl-CoA desaturase (SCD), that is able to desaturate several other fatty acids found in milk fat......