RESUMO
Conjugated linoleic acid (CLA), a naturally occurring anticarcinogen found in dairy products, is an intermediary product of ruminal biohydrogenation of polyunsaturated fatty acids. Our objective was to determine the effect of different dietary oils, which vary in fatty acid composition, on CLA concentrations in milk from lactating dairy cows. Twelve 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 (high oleic acid), sunflower oil (high linoleic acid) and linseed oil (high 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 (mean, 3.44% protein) was significantly higher (P < 0.01) than during the other treatments. Milk fat concentration of CLA during the sunflower oil treatment was significantly different from other treatments (P < 0.001) and approximately 500% greater than typically observed when cows consume 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 treatment, respectively. CLA concentration in milk fat can be enhanced by the addition of polyunsaturated fatty acids to the diet, especially oils high in linoleic acid.