Unravelling the Physiology of Cryptorchidism in Nigerian Indigenous Bulls: Endocrine, Histological, and Proteomic Characterisation

Cryptorchidism, the failure of one or both testes to descend into the scrotum, causes significant reproductive impairment and represents a heritable disorder with economic implications for bull stud programmes and beef cattle genetic improvement schemes. In Nigerian indigenous bulls including the White Fulani, Sokoto Gudali, and Keteku, the prevalence and physiological characterisation of cryptorchidism have not been systematically investigated using contemporary endocrine and molecular approaches. This study characterised cryptorchidism in Nigerian indigenous bulls through an integrative endocrine, histological, and proteomic investigation involving bulls from North West, North East, and North Central Nigeria. Seventy-two cryptorchid bulls confirmed by clinical and ultrasonographic examination were enrolled alongside 50 matched scrotal controls. Serum anti-Mullerian hormone, inhibin B, testosterone, luteinising hormone, and follicle-stimulating hormone were measured to characterise the endocrine profile. Testicular biopsies from cryptorchid testes and contralateral descended testes where available were processed for conventional histopathology and immunohistochemical characterisation of Sertoli cell markers including Sox9 and androgen receptor. Proteomic analysis of testicular interstitial fluid from cryptorchid and descended testes was performed by label-free quantitative mass spectrometry. Cryptorchid bulls showed significantly reduced inhibin B and elevated FSH compared with controls, consistent with Sertoli cell dysfunction. Anti-Mullerian hormone concentrations were paradoxically elevated in bilateral cryptorchid animals. Histopathology of cryptorchid testes showed spermatogenic arrest predominantly at the spermatocyte stage. Proteomic analysis identified 78 significantly dysregulated proteins in cryptorchid testicular fluid, with heat shock proteins and antioxidant enzymes significantly underrepresented. These findings advance understanding of the physiological basis of cryptorchidism in Nigerian indigenous bulls with implications for breeding soundness evaluation and surgical intervention criteria. Keywords: cryptorchidism, bulls, endocrinology, proteomics, Nigerian cattle.