[Use of norgestagens for estrus synchronization if farm animals].

The action of norsteroid type preparations and their capability of synchronising oestrus in heifer and sheep were studied at laboratory and clinical levels. The effectiveness of norethysterone acetate in heifer was tested by subcutaneous injections of 5 mg and 10 mg and did not exceed the order of 50 per cent. Combination of norsteroids with serum of pregnant mares increased slightly the number of animals with synchronised oestrus and improved the rate of fertilisation. Studies conducted into sheep revealed that no complete inhibition of the sexual function was ensured by injection of norgestrol acetate with prolongator in intervals of four days. Implantation of norgestrol acetate was not effective either. Further studies are required, before the above preparations can be applied to farm animals on a large scale.