MATURATIONAL CHANGES IN THE CHARACTERISTICS OF OESTROGEN-INDUCED SURGES OF LUTEINIZING HORMONE IN IMMATURE DOMESTIC GILTS

Abstract

Institute für Tierzucht und Tierverhalten, FAL, Mariensee, 3057 Neustadt 1, Federal Republic of Germany and * PES-Animal Physiology, University of Nottingham, School of Agriculture, Sutton Bonington, Loughborough, LE12 5RD (Received 19 April 1978) Possible causes of the variability in oestrogen-induced surges of luteinizing hormone (LH) in prepubertal miniature (Elsaesser, Parvizi & Ellendorff, 1978) and domestic (Foxcroft, 1978) gilts have been investigated. Four groups of six German Landrace gilts with indwelling jugular cannulae were kept under conditions of natural daylight. Groups A and C (60 and 161 days old respectively) received 60 μg oestradiol benzoate (OB)/kg body weight (Progynon Oleosum, Schering); groups and D (60 and 161 days) received 600 μg/kg body weight. Concentrations of OB (Elsaesser et al. 1978) and LH (Foxcroft, Pomerantz & Nalbandov, 1975) were determined in plasma samples taken at least every 12 and 4h, respectively, for 79·5 h after the i.m. injection of oil and for