Effect of lamb age, breed and sex on plasma LH after administration of GnRH.
Male lambs of the Finn, Fingalway and High Fertility breeds aged 4 or 8 weeks of age were injected i.m. with 5, 10, 50, or 100 micrograms GnRH. Plasma LH after GnRH injection increased with age and GnRH dose but there was no effect of breed. There was no interaction among the three factors studied. In a second experiment the response of male and female lambs, aged 8 weeks, to 100 micrograms GnRH was investigated for 5 genetic groups (Finn, Galway Control, Galway Elite, Fingalway and High Fertility). Breed differences in plasma LH of male lambs were not found, which agreed with the result of the first experiment. Breed differences were observed for females, with the lowest values being observed for Finn and High Fertility lambs which represent the two most prolific breeds. This finding suggested breed differences in the development of the hypothalamic-pituitary-ovarian circuit. The difference between Galway Control and Galway Elite lambs was not significant (P greater than 0.10).
D000367:Age Factors; D000818:Animals; D001947:Breeding; D004305:Dose-Response Relationship, Drug; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D007986:Luteinizing Hormone / Q000097:blood*; D008297:Male; D012737:Sex Factors; D012756:Sheep / Q000097:blood* / Q000235:genetics / Q000502:physiology
D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone