L-carnitine stimulates the transport of long-chain fatty acids across the inner mitochondria membrane to produce energy. It is synthesized with lysine and methionine as precursors. During lactation, the potential for biosynthesis of L-caritine in piglet has not yet developed, and so its supply depends on milk. The effects of L-carnitine supplementation to the feed of sows during pregnancy and lactation were demonstrated in earlier studies. The present study aimed to evaluate the effect of short-term L-carnitine supplementation in the following : on its concentration in milk during lactation, on the return of estrus, and on the growth performance of piglets. Fourteen crossbred sows with similar farrowing days were used at a commercial farm. They were classified into 2 groups ; a control group, in which sows were fed normal commercial feed ; and an L-carnitine-treated group, in which the feed included 50ppm of L-carnitine. Milking was conducted on days 0, 2, 3 and 11 after farrowing and the concentration of total, free and acetyl-form L-carnitine in milk were quantitatively analyzed. Milk yield was determined on days 1, 7, 14 and weaning by the weigh-suckle-weigh method. The number of piglets born, birth weight, deaths due to weakening, weaning weight, and the return date of estrus were recorded. The individual birth weight of piglets in the L-carnitine-treated group was significantly higher than that in the control group, but there was no significant difference in the litter weights at birth. Daily gain in the L-carnitine-treated group tended to be higher than the control group. For milk yield, the L-carnitine-treated group tended to be higher than the control group during week 1 with a decrease on the weaning day. On day 11 free L-carnitine concentrations in the L-carnitine-treated group were significantly (P<0.10) higher than that in the control group. Return of estrus tended to be earlier in the L-carnitine-treated group. The following results have been suggested : 50ppm supplementation of L-carnitine, even for short periods, positively affects the growth of piglets and return of estrus. This seemed to be due to the increase in the L-carnitine level in sow milk, and the better growth performance of piglets contributes to lessening the burden of lactation on sows.
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