Inhibin is a dimeric protein hormone composed of two dissimilar, disulphide-linked subunits (termed α and β) involved in the negative feedback regulation of gonadotrophin secretion, preferentially FSH. Interfering with this negative feedback by active immunization against inhibin has resulted in a consistent increase in ovulation rate and litter size in sheep. However, similar results have not been achieved in cattle. This paper describes the effect of active immunization of heifers against either of 3 synthetic peptide sequences from the bovine inhibin α-subunit on inhibin antibody titres, ovulation rate, calving rate and twin-calving rate.

Three peptide sequences from the bovine inhibin a-subunit were identified as likely immunological epitopes by computer analysis. These peptides (P1: bl-α-[YG] (18-30); P2: bl-α-(63-72)[GY]; P3: bl-α-[CG](107-122) were synthesized by solid phase methods and tyrosyl or cystenyl residues, linked through a glycine spacer where appropriate, were added during synthesis in order to facilitate iodination and conjugation respectively.