141 Effect of combined treatment of melatonin and equine chorionic gonadotrophin on fresh semen quality of Beetal bucks during the non-breeding season

Abstract

In the subtropics, bucks show seasonal breeding patterns, and their semen quality decreases during the non-breeding season. Therefore, breeders tend to improve bucks’ semen quality before the breeding season for higher conception rates. In the current study, we hypothesised that simultaneous administration of equine chorionic gonadotrophin (ECG) and melatonin would improve fresh semen quality in bucks before the breeding season. Nine Beetal bucks were randomly assigned (n = 3 per treatment) to three treatments: control, melatonin, and melatonin + ECG. Melatonin implants (18 mg; BTC Lab) were placed subcutaneously at the base of the ear. Bucks in the melatonin + ECG treatment were administered ECG (400 IU; Syncro-Part, Ceva Santé Animale) intramuscularly on every fourth day until the end of the experiment. Control bucks were administered normal saline (400 IU; Otuska Pakistan) intramuscularly on every fourth day. Semen was collected twice per week using an artificial vagina (42°C) and immediately evaluated for volume, color, pH, and contaminants. Sperm concentration, motility and kinematics (curvilinear velocity, straight-line velocity, average path velocity, and amplitude of lateral head displacement), viability, DNA, and acrosomal and mitochondrial integrity were monitored using a computer-assisted semen analyzer (AndroVision, Minitube). Weekly concentrations of plasma testosterone and melatonin of all bucks were analysed using radioimmunoassay (Immunotech, Beckman Coulter Ltd.) and enzyme-linked immunosorbent assay (450 nm), respectively. Comparisons within and between treatments were made using generalised linear models (repeated-measures analysis of variance). Weekly single-point variance between the treatments was determined (analysis of variance) at P ≤ 0.05 (SPSS ver. 20.0; IBM Corp.). Semen quality (volume, pH, total motility (%), and concentration) improved after Week 4 in the melatonin + ECG treatment compared with the control and melatonin treatments (P < 0.05). Similarly, progressive motility (%), viability, DNA, acrosomal and mitochondrial integrity, and sperm kinematics (curvilinear velocity, straight-line velocity, average path velocity, and amplitude of lateral head displacement) improved (P < 0.05) after Week 4 in the melatonin + ECG treatment. Similarly, non-viability and ratio of abnormal spermatozoa decreased by Week 3 in the melatonin + ECG treatment (P < 0.05) compared with the control and melatonin treatments. Likewise, plasma testosterone concentration (ng mL⁻¹) of bucks was higher (P < 0.05) at Week 3 in the melatonin + ECG treatment (4.2 ± 0.2) than in the melatonin (0.8 ± 0.1) and control (1.2 ± 0.1) treatments. Within the melatonin + ECG treatment, plasma testosterone concentration was higher (P < 0.05) at Week 5 (4.9 ± 0.2) and Week 9 (4.5 ± 0.1) than at Week 3 (4.2 ± 0.2). Plasma melatonin concentration (pg mL⁻¹) increased (P < 0.05) from Week 5 onward in the melatonin + eCG (12.5 ± 0.1) and melatonin (10.2 ± 0.1) treatments compared with the control (2.65 ± 0.1). In conclusion, the simultaneous administration of melatonin and ECG improved fresh semen quality in Beetal bucks.