Responses of dairy cows during early lactation to ruminal or abomasal administration of L-carnitine.

Six multiparous Holstein cows were used in a replicated Latin square to investigate the effects of carnitine administration into the rumen or abomasum. Treatments were 1) control, 2) twice daily ruminal administration of carnitine, and 3) continuous abomasal infusion of carnitine. Cows not receiving abomasal carnitine were infused continuously with an equal volume of water. Carnitine dosage was constant for both treatments (226 mg/kg of DMI; ca. 6 g/d). The diet fed to all cows contained 3% added fat. Carnitine concentrations in plasma and liver increased when carnitine was administered into either the rumen or abomasum, indicating that both sites of administration were equally effective at increasing carnitine concentrations in tissue. Milk yield, milk composition, and DMI were unaffected by carnitine supplementation, except for increased SNF content. Apparent digestibilities of lipid, energy, and total fatty acids increased with carnitine administration at either site. The concentration of VFA in ruminal fluid tended to increase with ruminal carnitine, and the percentage of propionate increased when carnitine was administered at either site. Retained N tended to increase when carnitine was administered, primarily because of greater retained N when carnitine was administered ruminally. Excretion of carnitine in milk and urine increased when carnitine was administered at either site. Carnitine supplementation increased concentrations of carnitine in plasma and liver and improved lipid digestibility.