Blood leptin concentrations in Japanese Black cattle

The objective of this study was to examine the changes of serum leptin leve ls in heifers and steers during fattening. Seven steers and seven heifers a t 14 months of age were used in the experiment. Line weight and serum lepti n levels were determined at 2-month intervals, initial live weight was grea ter in steers than heifers and a similar trend of growth was recorded durin g the experiment. As a result, live weight was higher in the steers than in the heifers during the experiment. Serum leptin concentration in both grou ps increased during the experiment and reached optimum level at 22 months o f age and did not change thereafter. The increase in serum leptin level was more marked in heifers and leptin level was higher (P < 0.05) in heifers t han steers between 18 and 26 months of age. The results suggest that serum leptin level increases during fattening in cattle and the trend is possibly affected by gender.