title: Neonatal immunisation against a novel gonadotrophin-releasing hormone construct delays the onset of gonadal growth and puberty in bull calves.
abstract: The aim of the present study was to investigate the effect of the neonatal immunisation of bull calves against a novel gonadotrophin-releasing hormone (GnRH) construct, comprised of GnRH coupled to the glycoprotein D subunit of the bovine herpes virus-1 (GnRH-BHV1 gD), on endocrine status, reproductive organ development and carcass quality. Eighteen bull calves received either GnRH construct (n=9) or saline (control; n=9) at 2, 6 and 13.5 weeks of age. Blood samples were taken to determine antibody titres against GnRH, FSH and testosterone (T) concentrations and LH pulse characteristics, with testicular circumference monitored monthly. Immunisation reduced LH pulse amplitude (P<0.05) and T concentrations (P<0.05), particularly at the peak in anti-GnRH titres after the second booster at 16 weeks of age (P<0.001), but not when titres fell. Despite antibody titres decreasing after 16 weeks, immunisation reduced testicular size between 16 to 57 weeks of age (P<0.05), provoking an 8-week delay in puberty onset, defined as testicular circumference ≥14 cm. In conclusion, neonatal immunisation induced a significant immune response against GnRH, provoking a temporary endocrine disturbance that had a long-term effect on testicular development, delaying the onset of puberty. These results support the hypothesis that a developmental window exists during testicular development, such that disturbance of the endocrine drive to the gonads during this period results in a longer-term impairment of gonadal function.
authors.affiliation: Division of Animal Sciences, School of Biosciences, The University of Nottingham, Loughborough, LE12 5RD, UK. juan.hernandez-medrano@nottingham.ac.uk
authors.forename: J H
authors.initials: JH
authors.lastname: Hernandez-Medrano
authors.forename: R W
authors.initials: RW
authors.lastname: Williams
authors.forename: A R
authors.initials: AR
authors.lastname: Peters
authors.forename: D
authors.initials: D
authors.lastname: Hannant
authors.forename: B K
authors.initials: BK
authors.lastname: Campbell
authors.forename: R
authors.initials: R
authors.lastname: Webb
mesh_terms: D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D000906:Antibodies / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D001823:Body Composition; D001835:Body Weight; D002369:Castration / Q000662:veterinary*; D002417:Cattle; D005640:Follicle Stimulating Hormone / Q000097:blood; D007987:Gonadotropin-Releasing Hormone / Q000276:immunology*; D007114:Immunization / Q000662:veterinary*; D007115:Immunization Schedule; D007986:Luteinizing Hormone / Q000097:blood; D008297:Male; D012741:Sexual Maturation; D013076:Sperm Count; D013081:Sperm Motility; D013737:Testis / Q000254:growth & development / Q000276:immunology* / Q000378:metabolism; D013739:Testosterone / Q000097:blood; D014764:Viral Proteins / Q000276:immunology*
chemical_list: D000906:Antibodies; D015415:Biomarkers; D014764:Viral Proteins; C046998:bovine herpesvirus type-1 glycoproteins; D007987:Gonadotropin-Releasing Hormone; D013739:Testosterone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone