Evaluation of a phytogenic blend supplementation on reproductive performance, antioxidant status, and immune function in broiler breeder roosters

Rooster fertility declines with aging, marked by reduced testicular weight, testosterone, semen quality, and antioxidant capacity, leading to lower hatching egg production and economic loss. This study evaluated the physiological effects and optimal inclusion rate of LibidoMax, a phytogenic supplement, on reproductive hormones, semen quality, antioxidant status, immune function, and metabolic biomarkers in aged broiler breeder roosters, using broken-line regression modeling. Twenty roosters (42 weeks old) were randomly assigned to four treatments (0, 100, 200, or 300 mL LibidoMax per 100 kg feed) for 70 days, including 14 days of acclimation. LibidoMax significantly enhanced serum levels of gonadotropin-releasing hormone (GnRH), luteinizing hormone (LH), follicle-stimulating hormone (FSH), and testosterone (P < 0.001). Broken-line regressions identified optimal hormonal plateaus between 182-190 mL/100 kg feed. Semen volume, sperm motility, viability, and concentration improved linearly, with breakpoints around 200 mL/100 kg feed, while sperm abnormality was minimized at ∼179 mL/100 kg feed. Hematological parameters improved with supplementation. Hemoglobin (HGB) and hematocrit (HCT) reached breakpoints at 176.5 and 179.6 mL/100 kg feed, respectively. Red and white blood cell counts (RBC and WBC) plateaued at 178.7-184.1 mL/100 kg feed, indicating enhanced oxygen transport and immune activation. Antioxidant enzymes, including total antioxidant capacity (T-AOC), glutathione peroxidase (GPx), and superoxide dismutase (SOD), peaked at ∼200 mL/100 kg feed, while malondialdehyde (MDA), a lipid peroxidation marker, was minimized at 100-110 mL/100 kg feed, reflecting early saturation of oxidative stress reduction. Lipid profiles were favorably modulated: triglycerides (TG), low-density lipoprotein (LDL), very low-density lipoprotein (VLDL), and total cholesterol decreased (breakpoints: 169-178 mL/100 kg feed), whereas high-density lipoprotein (HDL) peaked at 182 mL/100 kg feed. Liver enzymes, alanine transaminase (ALT), aspartate transaminase (AST), and alkaline phosphatase (ALP), were reduced at 170-180 mL/100 kg feed, indicating improved hepatic function. Principal Component Analysis (PCA) confirmed multivariate separation among treatment groups, with LibidoMax positively associated with reproductive, antioxidant, and immune enhancements and negatively with hepatic stress and lipid markers. In conclusion, 180-200 mL/100 kg feed represents the optimal inclusion range of LibidoMax to improve reproductive efficiency, immunity, and systemic health in aged breeder roosters.