EFECTO DEL NIVEL DE CONCENTRADO SOBRE EL PERFIL DE ÁCIDOS GRASOS DE LA LECHE DE VACAS HOLSTEIN EN PASTOREO EFFECT OF LEVEL OF CONCENTRATE ON MILK FATTY ACID PROFILE FROM GRAZING HOLSTEIN COWS

The content of conjugated linoleic acid (c9 t11 CLA) in milk depends mainly on the production in rumen of vaccenic acid, which is influenced by the supply of linoleic and linolenic acids in the diet. The aim of this study was to evaluate the effect of the level of concentrate on the production, composition and fatty acid profile of milk from nine Holstein cows in prairies with grass and legumes. The experimental design was a 3×3 Latin square and the treatments were: 1) 8 kg concentrate and 8 h on the prairie (8c); 2) 5 kg concentrate and 12 h on the prairie (5c), and 3) 3 kg of concentrate and 12 h on the prairie (3c). The data were analyzed with the SAS MIXED procedure and treatment means were compared with the Tukey test (p£0.05). Milk yield and fat, protein and lactose content were higher (p£0.05) in 8c treatment. The concentration of lauric, myristic and palmitic fatty acids (FA) increased in milk (p£0.05) with the increase of the concentrate level. The content of long-chain FAs ( ³C18) was higher (p£0.05) with 3 kg of concentrate, except for C18:2 c9c12. The reduction of the concentrate supplied to Holstein cows in prairies decreased the content of saturated FA, but increased the content of the unsaturated, particularly oleic, linolenic, vaccenic and c9 t11 CLA acids.