U.S. Department of Agriculture: Agricultural Research Service, Lincoln, Nebraska


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Published in J. Anim. Sci. (1991) 69:252-257


Prepubertal crossbred beef bulls served as controls or were actively immunized against the N-terminal, 30-amino acid synthetic fragment of porcine inhibin alpha, pIα,(1-30). Antibody titers were detected in sera (>40% B/Bo in sera diluted 1,000-fold) but not in rete testis fluid of 390-d-old bulls. Serum FSH and inhibin remained static during a 5-h intensive bleed; inhibin was not acutely affected by a 15-fold LH rise and a threefold FSH rise induced by exogenous GnRH. Serum FSH, but not LH or testosterone, was consistently elevated (P < .05) in immunized bulls compared with control bulls. Neither pituitary weight, pituitary gonadotropin content nor pituitary FSH/LH ratios were affected (P > .10) by pIα,(1-30) active immunization. Testicular sperm density was greater (60 x 106 vs 45 x 106 sperm/g testis; P < .10) in immunized bulls, but testes weight, epididymides weight and total daily sperm production remained unchanged. These results suggest that inhibin is important for regulation of FSH secretion and testicular function. Immunization with suitable inhibin vaccines may improve bull fertility.