[Hormonal methods of increasing fertility in swine]

Experiments were carried out to raise the conception rate in sows during the summer season under industrial conditions of breeding. Eight test groups of 365 animals were formed as well as four control ones with 137 pigs. The sucking period lasted 28 to 33 days. When in estrus the sows were mated with boars twice at a 24-hour interval. In five groups that were dried up from July to September was recorded the effect of several kinds of gonadotropic hormones administered alone or in combination with vitamin E and steroid hormones -- Gravohormone Tolligon, an oil emulsion of PMS (500 IU), with 250 Chorulon and 2 mg estradiol benzoicum; an oil solution of PMS (500 IU) with 2 mg estradiol, 25 mg testosterone and 30 mg vitamin E. During the same period three other groups of test sows were formed to use steroid hormones such as Gravignost, an oil solution of 2 mg estradiol benzoicum, and 40 mg testosterone propionate as well as the same preparation in combination with 30 mg vitamin E. The deterioration of the temperature and humidity regime in the summer at the industrial pig-breeding complexes was shown to inhibit the manifestation of estrus and lower the conception rate in sows. Either alone or in combination with vitamin E and estradiol the gonadotropic hormones largely raised the per cent of animals manifesting estrus for ten days in summer after weaning their piglets (89 to 100 per cent) as well as the number of lively born offsprings per sow (9.8 to 11.3). The optimal doses used were as follows: Gravohormone, 13--14 IU/kg liveweight; Folligon or PMS, 6--7 IU per kg; and choriogonadotropin at the rate of 500 IU per sow. One the other hand, the steroid hormonal preparations bring about estrus of a lower quality leading to a low conception rate and fertility at first insemination, disturb the sexual cyclicity. They should not be administered alone as cycle starters in pig-breeding.