Abstract
This study aimed to evaluate the effects of melatonin implants on the reproductive performances and hormone levels of dromedary (Camelus dromedarius) bulls during the non-breeding and subsequent breeding seasons. Fourteen mature dromedary bulls were divided into a control group (n = 7) and a group that was implanted with melatonin (n = 7) twice, at the beginning of the study and 35 days later. The trial started on the 17th June and continued for 10 weeks during the non-breeding season. Reproductive performances of animals in the control and melatonin groups were evaluated weekly during the non-breeding season [control non-breeding (CNB) and melatonin non-breeding (MNB) groups, respectively] and evaluated again during the subsequent breeding season [control breeding (CB) and melatonin breeding (MB) groups, respectively], which started on the 6th December and continued for 10 weeks. MNB bulls had greater (P <= 0.05) scrotum circumference and testicular volume, sexual desire, reaction time and mating ability scores, and serum melatonin and testosterone concentration values (24.91 +/- 0.26 cm, 271.00 +/- 7.81 cm(3), 231 +/- 0.13, 2.03 +/- 0.22, 2.26 +/- 0.09, 23.90 +/- 0.05 pg/mL and 2764.51 +/- 137.02 pg/mL, respectively) than the CNB group (23.63 +/- 0.05 cm, 199.21 +/- 3.27 cm(3), 1.00 +/- 0.00, 0.00 +/- 0.00, 1.00 +/- 0.00, 9.46 +/- 0.08 pg/mL and 1872.41 +/- 264.89 pg/mL, respectively). The scrotum and testes, reaction time score, proportion of bulls refusing to mount, and serum melatonin values were significantly higher in MB than CB bulls (P <= 0.05). Progressive motility (PM), average pathway velocity, straight-line velocity, curvilinear velocity (VCL), linearity, straightness (STR), wobble, beat cross frequency (BCF), livability, and DNA integrity were significantly higher in MB than CB bulls (P <= 0.05). PM, VCL, SIR, amplitude of lateral head displacement, BCF, and livability were significantly higher in MNB than CB bulls (P < 0.05). In conclusion, melatonin implants improved the reproductive performance of bulls during the non-breeding and subsequent breeding seasons. (C) 2018 Elsevier Inc. All rights reserved.