Chorionic gonadotropin administration in domestic cats causes an abnormal endocrine environment that disrupts oviductal embryo transport.

Fecal steroid analysis was used to investigate relationships between endocrine parameters and embryo characteristics in domestic cats subjected to chorionic gonadotropin stimulation and artificial insemination (AI). In Study 1, normal endocrine patterns were assessed in 12 cycling domestic queens. Fecal estradiol (E) patterns established an anovulatory cycle length of 18.3 +/- 0.4 d with estrus lasting 6.3 +/- 0.3 d. Eight females (67%) exhibited at least one spontaneous ovulation based on sustained increases in fecal progestagens (P). In Study 2, queens were mated during natural estrus (NE, n = 5) or subjected to exogenous i.m. gonadotropin stimulation, 100 IU eCG followed by 75 IU hCG 80 h later, (GS, n = 5). Compared with NE queens, fecal E concentrations were higher (P < 0.05) and remained elevated longer after ovulation induction with hCG. In Study 3, gonadotropin-stimulated queens (n = 7) were artificially inseminated and ovariohysterectomized 160 h after hCG. Ancillary follicles and/or corpora lutea were observed in 5 of 6 (83%) ovulating queens. Both fecal E and number of unovulated follicles observed at ovariohysterectomy were negatively correlated with the percentage of embryos recovered from the uterus (r = -0.91 and r = -0.87, respectively; P < 0.05). In summary, exogenous gonadotropin administration causes an abnormal endocrine environment in domestic cats, likely due to ancillary follicle development. The sustained elevations in estradiol appear to impair oviductal transport of embryos, possibly leading to the reduced fertility typically observed in cats subjected to gonadotropin stimulation and AI.