Relationship between number of induced ovulations in the prepubertal gilt to the level of progesterone and to the number of spontaneous postpubertal ovulations.

Abstract

A series of experiments were conducted to investigate the relationship between the number of corpora lutea (CL) and concentration of progesterone (P4) on different days after induced and spontaneous ovulation of gilts of different ages. Possible relationship between the number of ovulations after injection of gonadotropin into the prepubertal gilt and the number at a second induced ovulation and finally the number of postpubertal, spontaneous ovulations, was also studied. Number of CL was related (r = .75 to .95, P less than .01) to levels of P4 on d 3 to 10 after induced ovulation of prepubertal gilts of 105 to 180 d of age. Relationship between the number of CL and level of P4 in cyclic gilts ranged from r = .28 to .67 with the highest relationship at d 4 to 9. Number of CL induced at 135 d of age was correlated (r = .67 to .91, P less than .01) with number of CL induced at 195 d. There were correlations (r = .75 to .99, P less than .01) between levels of P4 and number of CL on d 7 to 9 after induction of ovulation of gilts of 135 and 195 d of age with either pregnant mare's serum gonadotropin (PMSG) followed in 96 h by human chorionic gonadotropin (hCG) or estradiol benzoate (EB) followed in 72 h by hCG. There was a correlation (r = .84, P less than .001) between number of CL at the first spontaneous postpubertal estrus and number of CL at third estrus.(ABSTRACT TRUNCATED AT 250 WORDS)