Relations between leptin and testosterone and glucose concentrations, fattening performance and reproductive development in growing bulls

This study were performed in 7 Brown Swiss and 7 Holstein bulls. The leptin concentrations at 12 months of age and testosteron concentrations at 9 months of age were statistically different between Brown Swiss and Holstein bulls (P < 0.05). In hip heights, a statistical difference at the level of P < 0.01 and P < 0.05 was observed at the 7, 11 and 12 months of age values and at the 8, 9 and 10 months of age values, respectively, between the two breeds of bulls. Furthermore, live weight gains and feed conversion values at 8 months of age were also significantly different (P < 0.05 and P < 0.01, respectively). Statistically negative correlations (P < 0.05) were observed between leptin concentrations and hip heights and scrotal circumferences of Brown Swiss bulls. The correlation was observed only between the leptin and testosteron concentrations in Holstein bulls (P < 0.05). In conclusion, the data obtained from Holstein bulls implies that leptin might be involved in growth and reproductive development, no association, however, was obtained between leptin and feeding performance