Dose response of dairy cows to abomasal administration of four amounts of L-carnitine.

Four Holstein cows were used in a 4 x 4 Latin square design with 21-d periods to determine the response to increasing amounts of L-carnitine infused into the abomasum. During d 1 to 7 of each period, cows were abomasally infused with 4 L/d of water; during the remainder of each period, 0, 3, 6, or 12 g/d of carnitine dissolved in 4 L of water were infused continuously into the abomasum. The DMI, milk yield, and milk composition were not affected by carnitine infusion. Apparent digestibilities of DM, OM, CP, ADF, NDF, and energy decreased linearly, and fatty acid digestibility tended to decrease linearly, when up to 12 g/d of carnitine were infused. Balances of energy and N generally were unaffected by carnitine infusion. The concentrations of carnitine in plasma and urine increased linearly, and that in milk increased quadratically, as the amount of infused carnitine increased; the concentrations of carnitine in plasma and milk appeared to be maximized when 6 g/d of carnitine were infused. Total carnitine excreted and carnitine excretion above basal excretion increased linearly as amounts of infused carnitine increased; however, < or = 23% of the daily carnitine dosage was excreted above basal carnitine excretion. Infusion of up to 12 g/d of carnitine into the abomasum did not improve milk yield or nutrient digestibilities.