Leptin and puberty in goat

Twenty four female kids (Serrana goat breed; weight 7,93±0,24 kg, age:93±2,6 d), were monitored from 3 months age (December) until the onset of puberty (October). At the beginning, kids were subdivided into three groups fed on hay ad libitum and different levels of concentrate: 30, 50 and 70% of dry matter intake (DMI) of concentrate for low level (LC), medium level (MC) and high level (HC), respectively. During the experimental period, the HC group grew at a higher rate, reaching a final BW higher (P<0.001) than the other two groups, but the total DMI did not vary between the experimental groups. The backfat depth was always significantly higher in the HC (P<0.001) compared with LC and MC groups. During the experimental period, mean concentrations of leptin did not differ due to diet; however, it significantly increased at puberty onset between August and October. Moreover, during this period plasma leptin levels were significantly correlated with both body weight (P<0.001) and backfat depth (P<0.01). The results indicate that in the goats the body weight, body fat depot and quality of diet influence the onset of the puberty, but not plasma leptin levels. The increase of plasma leptin during the onset of the puberty probably acts as permissive signal for the development of the sexual maturity and it can be used as a diagnostic tool to predict the imminent approaching of the event.