262 dairy cows were fed either 0 or 10g of a rumen protected carnitine product (containing 2g Carnitine) per cow and day supplemented via TMR. Milk yield and ingredients were investigated in all cows. For the investigation of blood parameters 55 cows per group were selected. Carnitin supplementation significantly decreased blood NEFA concentration one week a.p. and there was a trend for decreased NEFA one week p.p. and 5 weeks p.p.. GLDH in blood was significantly reduced one week a.p. and remained on a lower level throughout the trial in cows fed carnitine. Cholesterol level in blood was significantly decreased one week p.p. in heifers supplemented with carnitine. Cows in the supplemented group had also lower insemination index and improved conception rate.