DIETARY FATTY-ACID SOURCES AFFECT CONJUGATED LINOLEIC-ACID CONCENTRATIONS IN MILK FROM LACTATING DAIRY-COWS

Conjugated linoleic acid (CLA), a naturally occurring anticarcinogen f ound in dairy products, is an intermediary product of ruminal biohydro genation of polyunsaturated fatty acids. Our objective was to determin e the effect of different dietary oils, which vary in fatty acid compo sition, on CLA concentrations in milk from lactating dairy cows, Twelv e Holstein cows were randomly assigned to a 3 x 3 Latin square design. Dietary treatments were the addition (53 g/kg dietary dry matter) of peanut oil thigh oleic acid), sunflower oil thigh linoleic acid) and l inseed oil thigh linolenic acid). Each treatment period was 2 wk, and milk samples were collected on the last 4 d of each period. Milk yield (34.2 +/- 1.3 kg/d) and milk fat (2.25 +/- 0.06%) were not different among treatments. Milk protein during the sunflower oil treatment (mea n, 3.44% protein) was significantly higher (P < 0.01) than during the other treatments. Milk fat concentration of CLA during the sunflower o il treatment was significantly different from other treatments (P < 0. 001) and similar to 500% greater than typically observed when cows con sume traditional diets. CLA concentrations (mg/g of milk fat) were 13. 3, 24.4 and 16.7 during peanut oil, sunflower oil and linseed oil trea tment, respectively, CLA concentration in milk fat can be enhanced by the addition of polyunsaturated fatty acids to the diet, especially oi ls high in linoleic acid.