The current study was conducted to evaluate the effect of dietary camphor levels as a medicinal feed additive to improve semen quality, antioxidant capacity, reproductive hormones, and reproduction performance in roosters. For this purpose, thirty-five 29-wk-old Ross 308 broiler breeder roosters randomly were assigned to five experimental groups (seven birds/group) and received five doses of camphor containing 0, 50, 250, 750, and 1000 mg camphor/kg of feed for 12 wk consecutive. Semen quality parameters and motion characteristics of sperm were evaluated every 28 days and semen antioxidant capacity and plasma reproductive hormones concentration were tested at the end of the experiment. Also, at the end of the experiment, reproductive performance was assessed using artificial insemination. Among seminal quality parameters, sperm forward motility (88.96 vs 82.56%) and percentage of abnormal sperm (14.75 vs 15.86%) were improved in roosters fed 50 mg camphor/kg of feed compared to the control group (P < 0.05). Overall percentage of live sperm and plasma membrane integrity exhibited the quadratic responses to the levels of camphor (P < 0.08). The motion characteristics of sperm including progressive motility (28.81 vs 21.77%), average path velocity (VAP, 33.35 vs 26.83 μm/s), progressive velocity (VSL, 19.78 vs 16.48 μm/s), curvilinear line velocity (VCL, 52.87 vs 44.38 μm/s), the amplitude of lateral head displacement (ALH, 2.92 vs 2.46 μm) were improved in roosters fed 50 mg camphor/kg of feed compared to the control group (P < 0.05). However, dietary camphor levels linearly increased the percentage of linearity (LIN) and straightness (STR) (P < 0.05). A significant decrease in seminal plasma concentration of malondialdehyde (MDA) and an increase in superoxide dismutase (SOD) activity were observed in birds fed 1000 mg camphor/kg of feed (P < 0.05). Testosterone concentration was considerably increased by doses of 50 and 250 mg camphor/kg of feed compared to control (4.68, 4.79 vs 3.88 ng/mL) (P < 0.05). FSH and LH concentrations were not affected by camphor supplementation (P > 0.05). In the artificial insemination, fertility rate from both 50 mg camphor/kg of feed (88%) and 250 mg camphor/kg of feed (84%) was higher than control (75%) (P < 0.05). In conclusion, low levels of camphor, especially 50 mg camphor/kg of feed, improved seminal characteristics and, reproductive performance of roosters. Further researches are needed on the effect of higher levels of camphor and divulge of underlying mechanism on male's reproductive function.
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