The relationships between leptin and insulin in blood plasma of growing lambs

Abstract

AbstractThe present study was designed to examine the pattern of changes in plasma leptin concentration during the early stage of young ruminants. Five crossbred lambs weaned at 45 days were housed individually in pens. The lambs were offered timothy hay, rolled barley and soya-bean meal to meet a 200 g daily gain, and were given free access to water and mineral block. Blood samples were collected just before the morning feeding and at 30-min intervals for 6 h after the morning feeding beginning at 0·5 months after weaning and thereafter monthly for the next 6 months. Plasma leptin level increased dramatically from 0·5 to 3 months after weaning. Thereafter, it dropped to a similar level to that at 2 months after weaning and remained at that level. Moreover, plasma leptin level was not affected by feeding, and no variation throughout the day of sampling was observed. Plasma insulin levels showed similarity to changes in plasma leptin levels. Plasma insulin levels were positively correlated (r = 0·63) with plasma leptin levels. This study shows that plasma leptin level dramatically increases after weaning. Additionally, it suggests that insulin contributes to the increase of leptin with growth in lambs.