110 EFFECT OF MELATONIN TREATMENT ON LIBIDO AND ENDOCRINE FUNCTION OF DROMEDARY CAMEL BULLS OUT OF THE BREEDING SEASON

Abstract

The reproductive performance of camels is poor and has remained a major obstacle to the growth of dromedary populations. The limited breeding season is one of the most important causes of the poor reproductive performance. In seasonal animals, melatonin is the chemical messenger that allows the perception of daylight length changes. Commercial melatonin products have been developed for the manipulation of seasonal breeding in animals. The present study aimed to evaluate the influence of melatonin implantation on libido, serum melatonin, and testosterone concentrations in dromedary camels during the non-breeding season (June and July). Ten camel bulls were used in the 35-day-long trial; 5 of them were implanted with 30 Melovine® implant (Ceva, Libourne, France) subcutaneously on Day 0, whereas the other 5 camel bulls remained untreated as a control. Libido was evaluated weekly in response to oestrous-induced female camels treated with oestrogen (1 mL Oestrocon; oestradiol benzoate 5 mg mL⁻¹) 2 days before assessment of libido. Libido was scored as follows: 0 = not interested: the male did not show any libido; 1 = low interested: the male went near the female and showed low frequency of sniffing and flehmen; 2 = interested: the male went near the female, it showed sniffing, flehmen, grinding of teeth/whistling, yawning; 3 = high interested: the male went near the female and was very agitated, it showed sniffing, flehmen, grinding of teeth/whistling, yawning, urination, and tail raising. It stood with open legs, and poll gland secretion and neck rubbing were observed; 4 = excited, like 3, but the male showed blatering and dulaa extrusion, was very excited, stood with open legs, high poll gland secretion and neck rubbing were observed. Blood samples were collected weekly. Serum melatonin and testosterone concentrations were evaluated using commercial ELISA kits. Comparisons among groups were evaluated using repeated-measures ANOVA, using SAS software (SAS Institute Inc., Cary, NC, USA). A difference was considered significant at the P < 0.05 level. The results revealed that at Day 0, all camel bulls in 2 groups had no libido and there was no significant difference in the melatonin or testosterone levels in the 2 groups. The libido increased gradually in the melatonin group and reached the maximum (3–5) at week 4 and week 5. The control group had low libido (0–1) along the trial. Statistically, the libido was significantly higher in the melatonin group than control group. Additionally, testosterone levels were significantly higher in melatonin group than control group, especially in the fourth week of the present trial (565.07 ± 33.04 pg mL⁻¹ and 458.49 ± 25.36 pg mL⁻¹, respectively). In conclusion, melatonin implantation in the non-breeding season significantly improved the libido and the reproductive performance of dromedary camel bulls. Therefore, it may be possible to improve the reproductive efficiency of camels by extending the breeding season through treatment with melatonin during the non-breeding season.