[Experimental endocrinological studies in gilts near the time of ovulation using Gn-RH vet. "Berlin Chemistry"]

Knowledge of endocrine processes in pro-oestrus and oestrus in conjunction with physiological alterations is of greatest importance to biotechnological control of follicular maturation and ovulation. Methods of hormonal analysis and ovarian diagnosis were used to check on the effectiveness of Gn-RH vet. "Berlin-Chemie" for induction of the luteinising hormone (LH) peak and ovulation. Release in gilts of LH was found to depend on dosage, after 100, 300, and 900 micrograms Gn-RH had been administered at 3 p.m. on the 4th day after synchronisation of ovulation. LH release and induction of ovulation due to these variants were insufficient in some of the animals. Ovulation was then decisively improved in animals with LH peak by subsequent injection of 300 or 900 micrograms Gn-RH at 8 a.m. on the 5th day. Repetitive injections of 300 micrograms Gn-RH at 8 and 8.45 a.m. on the 5th day did not trigger off increased LH release from the pituitary gland. The Gn-RH effect was substantially improved by use of an absorption-retarding preparation (polystyrene sulphonic acid).