The goal of this study was to evaluate the effects of different L-carnitine concentrations on post-thaw rooster semen parameters. Ten sexually mature Ross-308 roosters (35 weeks of age) with confirmed fertility were used in the six replicates of this experiment. Semen samples (n = 30, 6 samples per rooster) were collected using an artificial vagina twice a week. Following the collection and initial assessment of ejaculates, all semen samples were pooled to eliminate individual variations. The Lake freezing extender was supplemented with varying concentrations of L-carnitine (0, 2.5, 5, 10 and 20 mM), and semen was diluted to a final concentration of 100 × 106 spermatozoa/0.25-mL straw before freezing in liquid nitrogen. Rooster semen cryopreserved in a freezing extender supplemented with 5 mM of L-carnitine exhibited the highest (P ≤ 0.05) percentages of sperm with total/progressive motility and average path velocity, as well as spermatozoa with intact mitochondria, plasma membranes, and acrosomes. This dose of the additive was also associated with the highest (P ≤ 0.05) fertility percentage in artificially inseminated hens and with the lowest (P ≤ 0.05) levels of apoptosis, DNA fragmentation, ROS accumulation, and lipid peroxidation compared with other doses of L-carnitine tested. Therefore, supplementing the Lake freezing extender with 5 mM of L-carnitine is an effective method for preserving the quality and fertilizing potential of cryopreserved rooster semen.
