FSH-stimulated follicle development in ewes in high and low body condition and chronically treated with gonadotrophin-releasing hormone agonist

Ovarian follicle development in response to FSH infusion was investigated in Scottish Blackface ewes with high and low body condition scores in which endogenous gonadotrophin secretion and follicle development to ≥2.5 mm diameter was suppressed using subcutaneous implants containing a GnRH agonist. In two experiments conducted during the normal breeding season, groups of 20 (Expt 1) and 15 (Expt 2) ewes were fed to achieve body condition scores ≥2.75 (high; H) or ≤1.75 (low; L). In both experiments GnRH agonist implants were inserted four weeks before FSH was infused for 72 h at 7 μg h -1 to group H animals or at 5 μg h -1 to group L animals; the infusion rates were designed to ensure similar circulating FSH concentrations in animals of both groups