title: Effect of immunization of rams against bovine inhibin alpha 1-26 on semen characteristics, scrotal size, FSH, LH and testosterone concentrations.
abstract: The effects of inhibin immunization on inhibin antibody titres, semen characteristics, scrotal size, fertility, FSH, LH and testosterone concentrations were determined by immunizing adult rams against bovine inhibin alpha 1-26-Gly-Tyr conjugated to human serum albumin (n = 16) in non-ulcerative Freund's adjuvant and DEAE:dextran (1:1) or adjuvant alone (n = 16) on days 0 (29 June), 30, 60, 191, 303 and 394. Blood samples were collected and bovine inhibin alpha 1-26-Gly-Tyr antibody titres and serum testosterone concentrations were determined. Each month, between days 174 and 417, semen was collected every 30 min to a maximum of 15 ejaculates over 7 h and scrotal circumference was measured. Ram fertility was recorded during natural service. FSH, LH and testosterone concentrations and GnRH-induced FSH and LH release were measured in a subgroup of immunized (n = 5) and control (n = 5) rams at frequent intervals. Antibody titres were variable among immunized rams (0-46% 125I-labelled bovine inhibin alpha 1-26-Gly-Tyr at 1:1600 serum dilution) but mean titres were consistently higher than in control rams (P < or = 0.001). Immunization did not alter the semen volume, output or quality of spermatozoa or ram fertility, but increased the mean scrotal circumference (37.6 +/- 0.8 cm versus 34.4 +/- 0.7 cm, P < 0.001). Mean FSH concentrations were higher in immunized rams during two intensive blood sampling periods (in June and August) (5.8 +/- 0.7 ng ml-1 versus 3.0 +/- 0.3 ng ml-1, P < 0.001 in June; and 4.8 +/- 0.9 ng ml-1 versus 2.0 +/- 0.3 ng ml-1, P < 0.02 in August), and were correlated with antibody titres (r2 = 0.3, P < 0.05 in June; and r2 = 0.8, P < 0.001 in August). Discrete FSH pulses were not detected. Immunization did not alter mean or basal testosterone or LH concentrations, or LH pulse frequency; LH pulse amplitude was increased (1.6 +/- 0.2 ng ml-1 versus 0.8 +/- 0.2 ng ml-1, P < 0.02) and was correlated with antibody titres (r2 = 0.6, P < 0.01). Immunization enhanced GnRH-induced FSH (P < 0.05) but not LH release. In conclusion, immunization of adult rams against bovine inhibin alpha 1-26 Gly-Tyr increased scrotal circumference, mean FSH concentrations and LH pulse amplitude, without altering semen characteristics, fertility, mean LH concentrations, LH pulse frequency or mean testosterone concentrations.
authors.affiliation: Faculty of Agriculture, University College Dublin, Belfield, Ireland.
authors.forename: R M
authors.initials: RM
authors.lastname: McKeown
authors.forename: D
authors.initials: D
authors.lastname: O'Callaghan
authors.forename: J F
authors.initials: JF
authors.lastname: Roche
authors.forename: M P
authors.initials: MP
authors.lastname: Boland
mesh_terms: D000818:Animals; D000906:Antibodies / Q000097:blood; D005640:Follicle Stimulating Hormone / Q000097:blood; D006065:Gonadotropins, Pituitary / Q000097:blood*; D007114:Immunization; D007265:Inhibins / Q000276:immunology / Q000502:physiology*; D007986:Luteinizing Hormone / Q000097:blood; D008297:Male; D010446:Peptide Fragments / Q000276:immunology; D012611:Scrotum / Q000033:anatomy & histology*; D012661:Semen / Q000502:physiology*; D012756:Sheep; D013076:Sperm Count; D013094:Spermatozoa; D013739:Testosterone / Q000097:blood*
chemical_list: D000906:Antibodies; D006065:Gonadotropins, Pituitary; D010446:Peptide Fragments; C106049:inhibin alpha 1-26; D013739:Testosterone; D007265:Inhibins; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone