Evaluation of Semen Biochemical Quality Indicators and Their Relationship to Fertility Outcomes in Sahiwal Breeding Bulls in Sokoto State, North West Nigeria

Semen biochemical quality indicators provide a functional complement to conventional semen morphology and motility assessments in predicting bull fertility outcomes. This study evaluated semen biochemical quality indicators and their relationship to field fertility in Sahiwal breeding bulls at the Usmanu Danfodiyo University Bull Station in Sokoto State, North West Nigeria. Twenty-four Sahiwal bulls used for natural service were enrolled over two successive breeding seasons. Ejaculates were collected by electroejaculation and assessed for conventional semen parameters alongside biochemical markers including fructose, citric acid, seminal plasma zinc, total antioxidant capacity, and malondialdehyde. Field fertility was estimated by pregnancy diagnosis of served cows at sixty days post-service. Bulls with pregnancy rates exceeding 65% had significantly higher seminal plasma total antioxidant capacity and zinc concentrations compared to those with pregnancy rates below 50%. Malondialdehyde was inversely correlated with pregnancy rate. Fructose concentrations did not differ between high- and low-fertility bulls, but citric acid was significantly elevated in high-fertility animals, suggesting greater accessory gland secretory function. A composite fertility score incorporating conventional motility, total antioxidant capacity, and zinc predicted pregnancy rate with 78% accuracy in cross-validation. This study supports the use of semen biochemical markers as adjuncts to conventional andrological evaluation in bull selection programmes in North West Nigeria. Keywords: semen biochemistry, bull fertility, antioxidant capacity, Sahiwal bulls, Sokoto.