Plasma leptin, feed intake and body fat accumulation in fattening castrated male and female lambs

The main objective of this study was to investigate the relationships between changes in plasma leptin concentration and feed intake or bodyweight in female and castrated male lambs with fattening. Four female and four castrated male lambs were used and were fed roughage and concentrate supplemented with beef tallow ad libitum for 28 weeks. Although the feed intake and bodyweight increased with fattening in both the castrated male and female lambs, they decreased at 24-28 weeks in the female lambs. At the end of fattening, the crude fat content in the muscle (loin) of the female lambs was significantly higher than in the castrated male lambs (P0.05), while the crude protein content in the loin and fillet meat was higher in the castrated male than in the female lambs (P0.05). The plasma leptin concentration showed high values at a later stage of fattening (P0.05). In the female lambs the plasma insulin concentration increased at a later stage of fattening (P0.05) and was positively correlated (P 0.0001, r