Effect of melatonin supplementation on sperm quality in dromedary camel (Camelus dromedarius) under physiological and...

Melatonin, a potent antioxidant, has shown protective effects in other species, however, the optimal dose range and dose-dependent effects of melatonin on dromedary camel sperm quality under physiological conditions and short-term cold-storage conditions remain limited. This study evaluated the dose-dependent effects of melatonin on sperm kinematics parameters, viability, membrane integrity, and DNA fragmentation in dromedary camels under physiological incubation (36 °C) and after short-term cold storage (4 °C). Semen from four healthy adult males was collected and pooled into six composite samples to minimize inter-male variability, then allocated to five melatonin doses (0, 0.5, 1, 2 and 3 mM) under vehicle-matched conditions. Sperm quality was assessed using computer-assisted sperm analysis, hypo-osmotic swelling (HOS) test, eosin-nigrosine viability, and Sperm Chromatin Dispersion test (SCD). Data were analysed with mixed-effects models, and pairwise differences were assessed using Tukey-Kramer tests (α = 0.05). Results showed that melatonin improved multiple sperm quality traits at physiological temperature and during short term cold storage. A clear dose window (1-2 mM) yielded the most balanced protection of motility, viability (improved by 22.1% compared to control), membrane integrity (improved by 19.1%), and DNA stability (reduced fragmentation by 30.2%), whereas the 3 mM dose resulted in a plateau effect, offering no further enhancement in sperm preservation. This study revealed that melatonin may represent a promising additive for camel semen handling and short-term preservation, with 1-2 mM appearing as the most effective range for extenders.