Dictyota dichotoma extract as a potential nutraceutical for male fertility: insights into semen quality, testicular histology, immunomodulation, and anti-inflammatory markers in rabbit bucks

This study investigated for the first time the potential symbiotic effects of using Dictyota dichotoma extract (DDE) to enhance reproductive health in bucks. The study examined semen quality, immune function, blood biochemistry, inflammatory markers, antioxidant status, testicular histology, and seminal plasma contents in rabbit bucks. A total of forty bucks (n = 10 in each group) were randomly allocated into four groups and fed a basal diet with 0, 100, 200, and 400 mg of DDE/kg diets for 3 months. The results indicated that DDE (200 mg/kg) treatment linearly enhanced sperm concentration, membrane function, motility, and viability (P < 0.01), while significantly reducing sperm abnormalities in a quadratic trend (P < 0.05). Serum concentrations of total glycerides and lactate dehydrogenase decreased linearly, while creatinine, gamma-glutamyl transferase, and urea levels exhibited a significant quadratic reduction (p < 0.01) in rabbits fed DDE-supplemented diets. Dietary DDE (200 or 400 mg/kg) inclusion linearly increased plasma SOD, GPX (quadratic effect, p < 0.01) and catalase activities, while quadratically decreased MDA levels (p < 0.01). Immunological parameters, including IgG and nitric oxide levels, exhibited a significant linear increase (p < 0.01) with the best dose 200 mg of DDE supplementation. Similarly, IgM levels and lysozyme activity were quadratically improved in groups fed DDE-fortified diets (p < 0.01). DDE supplementation (400 mg /kg) quadratically reduced capaspae-3 and IFN-γ (p < 0.01) and linearly decreased Bcl-2 (p < 0.01). In contrast, cytochrome C levels were quadratically enhanced across the DDE treatment groups (p < 0.01). DDE inclusion linearly improved seminal antioxidant activities SOD, and CAT and quadratically improved GPX (p < 0.01). Additionally, seminal plasma MDA levels were linearly reduced by DDE treatment (p < 0.01). In sperm cells, the activities of mitochondrial enzymes such as MDH (quadratic effect, p < 0.01) and SDH (linear effect, p < 0.001) were significantly improved in all DDE-supplemented groups compared to the control group. Histology, the DDE treatment enhanced the testicular integrity as evidenced by an increase in the numbers and diameters of seminiferous tubules (ST), as well as the heights of the germinal epithelium of ST (p < 0.05). Overall, dietary inclusion of DDE may have beneficial effects on the reproductive health of bucks by regulating sperm function, blood health, improving antioxidant and immune responses, and reducing inflammatory signaling.