Oral administration of black seed oil or its nano-emulsion enhances testicular hemodynamics, testosterone concentration, nitric oxide level, semen quality, and total antioxidant capacity in Ossimi rams during heat stress.

Heat stress (HS) severely impairs reproductive performance and testicular function in livestock. This study aimed to evaluate the comparative efficacy of conventional black seed oil (BSO) and its nano-emulsion (BSO-NE) in mitigating summer thermal stress in Ossimi rams. Fifteen mature rams were divided into three groups (n = 5 each) and treated orally daily for 8 weeks during summer: a water-treated control, a BSO group (0.5 mL/kg body weight (BW)), and a BSO-NE group (0.05 mL/kg BW). Testicular ultrasonography, semen characteristics, and blood markers were monitored weekly, following a two-week winter baseline assessment in February. Results showed that BSO-NE significantly decreased (P < 0.05) testicular Doppler indices: specifically, the resistive index (RI) from weeks 2-4, pulsatility index (PI) at weeks 2 and 7, and systolic/diastolic ratio (S/D) at week 1, while producing the highest systemic concentrations (P < 0.05) of nitric oxide (NO) and testosterone from weeks 1-8. Consequently, BSO-NE significantly increased (P < 0.05) sperm motility, viability, normal morphology, and acrosome integrity from weeks 2-8, alongside increasing sperm cell concentrations from weeks 6-8. Furthermore, BSO-NE exhibited the most pronounced upregulation (P < 0.05) in total antioxidant capacity (TAC) and superoxide dismutase (SOD) from weeks 3-8, catalase (CAT) and glutathione peroxidase (GPx) from weeks 4-8 relative to the other cohorts. To summarize, oral supplementation of BSO-NE effectively counteracts seasonal HS in Ossimi rams, thereby maintaining reproductive performance through improved testicular blood flow and enhanced sperm quality.