Clinical and endocrine responses to embryonic and fetal death induced by manual rupture of the amniotic vesicle during early pregnancy in cows.

Pregnancy was terminated in 4 cows by manual rupture of the amniotic vesicle on day 41 (n = 1) and day 46 (n = 3) after insemination. Each cow was necropsied 36 days after vesicle rupture, by which time only one cow had come into estrus. Luteal activity, monitored daily by plasma progesterone assay, was still evident in 2 cows 35 days after fetal death; in the remaining 2 cows, regression of the corpus luteum (CL) was achieved at 28 and 32 days, respectively. Uterine release of prostaglandin F2 alpha (PGF2 alpha), measured as the 15-keto metabolite (PGFM) PGF2 alpha, was monitored by a plasma sampling schedule; specimens were obtained every 4 hours. There were no appreciable releases of PGF2 alpha associated with fetal death. The first appreciable PGF2 alpha release in episodic form was seen only in conjunction with CL regression. In all cows, a palpable membrane slip was evident for 18 days after rupture of the amniotic vesicle, although at that time, uterine resilience was diminished in the 2 cows in which the CL subsequently regressed. After 18 days, the uterus was noticeably edematous and fluid-filled in all cows; in 1 of the cows with a regressed CL, the uterus had returned to prepregnancy size and tone by day 33.(ABSTRACT TRUNCATED AT 250 WORDS)