Recent studies have shown that L-carnitine supplementation of sows increases growth of their piglets during the suckling period. In this study, the composition of the milk of sows supplemented with L-carnitine was determined to find out whether an altered milk composition could account for the increased growth rates of the piglets. Milk of 13 control sows and 14 sows supplemented with L-carnitine (125 mg/d during pregnancy, 250 mg/d during lactation) was collected 5-8 h after birth (colostrum) and on days 10 and 20 of lactation. Concentrations of fat and lactose and the energy content in milk at day 10 and 20 did not differ between both groups of sows. Sows supplemented with L-carnitine had a higher concentration of protein in colostrum (p < 0.05) while concentrations of fat, lactose, immunoglobulins G, M and A as well as the energy content in colostrum did not differ between both groups of sows. These findings show that milk composition does not play a major role for the increased postnatal growth of piglets from sows supplemented with L-carnitine observed in recent studies.