The present study investigated the effect of L-carnitine supplementation during pregnancy (125 mg/d) and lactation (250 mg/d) on milk production, litter gains and back-fat thickness in sows fed a low-energy and low-protein diet during lactation. Sows supplemented with L-carnitine produced more milk on days 11 and 18 of lactation (+18 %; P<0.05) and had higher litter gains during suckling (+20 %; P<0.01) than control sows. Loss of body weight during lactation was similar in both groups, but sows supplemented with L-carnitine had a greater reduction of back-fat thickness (+45 %; P<0.05) during lactation than control sows. In conclusion, this study shows that L-carnitine increases milk production and litter gains in sows in a strongly negative energy and N balance, and enhances body fat mobilisation.