Estrus and ovulation in gilts fed a synthetic progestogen.

A synthetic progestogen, allyl trenbolone (AT), was fed to sexually mature gilts to determine the effective doses for the control of estrus and ovulation. Gilts were assigned to a control group and 5 treatment groups receiving 10.0, 12.5, 15.0, 17.5 or 20.0 mg of AT mixed in .45 kg of feed/head/day for 18 consecutive days. Ovarian morphology was determined by laparotomy following estrus or at 10 days post-treatment. AT suppressed estrus in all gilts during treatment. Estrus was effectively synchronized in treated gilts. The average interval from withdrawal of progestogen treatment to estrus was 4.5 days for 48 of 50 treated gilts that were in estrus within 10 days after treatment. The average ovulation rate in treated gilts was similar to control gilts. No detrimental side effects, due to treatment, were observed with the possible exception of a slight increase in the incidence of cystic follicles.