106 Exogenous melatonin administration improves behavioural signs, serum melatonin, testosterone, and semen quality in male dromedary (Camelus dromedarius) camels

Abstract

The present study aimed to evaluate the effects of exogenous administration of melatonin to male camels on reproductive behaviour, seminal parameters, and serum concentrations of melatonin and testosterone during the non-breeding and subsequent breeding seasons. In September 2018, male camels (n = 12) were randomly allocated to subcutaneous injections of either melatonin (MLT, 0.643 mg/kg; n = 6) dissolved in corn oil, or plain corn oil; (control n = 6). The camels were observed for behavioural signs of rut. A second dose of either MLT (1 mg/kg) or corn oil (control) was administered on 7 October 2018 subcutaneously, as camels did not show any change in behaviour until 6 October 2018, and the camels were again observed for behavioural signs of rut. Blood was collected from all camels on 1 September 2018, and then at weekly intervals until 7 January 2019. The serum was separated and stored until further assay of serum melatonin and testosterone using ELISA kits. Semen was collected from camels showing signs of rut period, and the reaction time, copulation time, and seminal parameters were evaluated. Data obtained was analysed by using the computer program SPSS (version 25; IBM Corp.), and means and standard errors were compared. Male reproductive behaviours (protrusion of soft palate, poll gland secretions, frequent urination, increased frothy salivation) were more pronounced in MLT-treated camels (83.33%) than in control camels (50%). Reaction time and copulation times were lower (112.81 ± 30.06 s and 229.8 ± 37.91 s) in MLT-treated camels than in controls (359.00 ± 41.35 s and 301.89 ± 93.90 s). Higher semen volume was observed in MLT-treated (5.34 ± 2.06 mL) than in control (3.11 ± 1.75 mL) camels (P < 0.01). Semen collected from MLT-treated camels had more gel formation (81.25%), significantly higher sperm motility (67.50 ± 2.32%), and increased sperm concentration (326.56 ± 38.67 million mL⁻¹) compared with samples obtained from the control males (P < 0.01). Serum melatonin concentrations increased in both treated and control camels during the breeding season compared with concentrations before the breeding season. In MLT-treated camels, serum melatonin concentrations increased significantly and continued to be significantly higher than that in control camels for the entire study period (P < 0.01). Serum testosterone concentrations were higher in both MLT-treated and control camels during the breeding season compared with those during the non-breeding season (P < 0.01). We concluded that exogenous subcutaneous MLT administration improves sexual behaviour, seminal parameters, and serum testosterone concentrations during both the non-breeding and breeding seasons.