Akademik Veri Yönetim Sistemi
Journal of Animal and Veterinary Advances, cilt.8, sa.10, ss.2033-2037, 2009 (SCI-Expanded)
This study was undertaken to investigate the effects of melatonin on the initiation of the breeding season in female cats. 12 female cats and 2 tomcats (male cats, vasectomized) aged 2-6 years old were used. The female cats were randomly divided into control (group I, n=6) and melatonin-treated groups (group II, n=6). Sham (placebo) and melatonin implants (containing 18 mg of melatonin) were placed subcutaneously into the females during the late anoestrus in groups I and II, respectively. The sexual behaviours, vaginal smears and serum progesterone levels of the animals were recorded. The effect of daylight (varying from 9.5-12.5 h, December to April) on the cyclic activity was also assessed during the study period. The animals were sexually silent during the anoestrus period. Upon the commencement of the breeding season, the female cats in group I showed oestrus signs, but only one of the female cats in group II showed the indications of the oestrus. Moreover, the findings of cytology were insignificantly different in both groups during the study period (p≥0.05). Although the progesterone levels in the breeding season were higher in group I (p≤0.05) than in the non-breeding season, no such difference was present in group II. The progesterone levels during the breeding season were markedly elevated (p≤0.01) in group I compared to group II. In the latter group, melatonin effectively postponed the cyclic activity of the females. The results suggested that the administration of exogenous melatonin might prolong the non-breeding season, presumably via the suppression of hypothalamic centres. Moreover, exposure to daylight of 10.5 or more hours per day was also sufficient for the onset of cyclic activity in the female cats.