Administration of testosterone during the follicular phase increased the number of corpora lutea in gilts.

The effects of 0 (vehicle), 1, 10, or 100 mg of testosterone, administered on d 17 and 18 of the estrous cycle (d 0 = 1st d of estrus), on the number of preovulatory follicles on d 19 or the number of corpora lutea (CL) and blastocysts on d 11 of the subsequent cycle were examined in 82 gilts. The mean number of preovulatory follicles increased (P < .01) in a dose-dependent manner. Likewise, gilts that received 1, 10, or 100 mg of testosterone had more (P < .05) CL than gilts treated with vehicle. The mean number of blastocysts increased (P = .06) in gilts receiving 1 mg of testosterone but decreased (P < .05) in gilts treated with 10 mg of testosterone compared with gilts receiving vehicle. Similarly, recovery rates of blastocysts decreased (P < .05) in gilts treated with 10 or 100 mg of testosterone relative to gilts administered 0 or 1 mg of testosterone. Plasma concentrations of testosterone and estradiol increased (P < .05) 2 h following administration of 1 mg of testosterone on d 17 of the estrous cycle. These results indicate that although the 10- and 100-mg dosages of testosterone were detrimental to blastocyst survival, the 1-mg dosage increased synthesis of estradiol and the number of CL and d-11 blastocysts.