Concentrazione ematica della malatonina in capre di razza Maltese e Siriana

Melatonin blood levels in Maltese and Syrian goats. The melatonin blood concentration has been studied on 10 adult goats of two southern Italian breeds (5 Maltese and 5 Syrian), which are characterized by a weak reproductive seasonality, presenting a spring breeding period in addition to the main autumn season. The animals were kept under natural photoperiod, were bred in autumn and displayed regular deliveries and lactations. The plasma melatonin concentration was assayed by RIA on blood samples taken at 2 h interval for 24 h. Night samples were taken in dim red light. The sampling sessions were repeated at 2 months interval for one year. During the daylight period the hormone levels were very low (< 4 pg/ml), while during night time in each sampling session the concentrations arised in all the animals, with high individual variability (the individual mean night levels ± SE ranged from 6.41.9 to 109.162.4 pg/ml). Each animal maintained during the year higher or lower nocturnal melatonin levels in comparison to those of the other goats, and significant (P<0.05) differences in the night mean values between the animals have been found. The Syrian goats showed lower (P<0.05) mean night levels (20.052.30) than the Maltese ones (55.349.23 pg/ml), two goats with the higher mean values being Maltese. No significant seasonal differences in the mean melatonin nocturnal levels resulted from our data: the lowest mean night values were recorded in Aug, the highest in Oct. . It would be interesting to investigate if the significant individual variability in nocturnal melatonin plasma concentrations found in the present work might be someway linked to individual variability in the parameters of the reproductive seasonality.