Induction of hydrometra in goats by means of active immunization against prostaglandin F2 alpha.

Hydrometra is a pathological condition of the uterus which is characterized by accumulation of aseptic fluid in the presence of a persistent corpus luteum. It forms a major cause of subfertility in goats. Active immunization against prostaglandin F2 alpha (PGF2 alpha), the luteolytic hormone in this species, was used to explore the possibility for artificial induction of this pseudopregnant condition. During the breeding season, 11 goats (group I) were immunized with 5 mg PGF2 alpha-ovalbumin conjugate in Freund's complete adjuvant, 4 goats were control-immunized (group CI) and 5 goats remained untreated (group C). Jugular blood samples were taken twice a week (monday and thursday) for measurements of plasma progesterone and binding of 3HPGF2 alpha. In conjunction with blood sampling, transcutaneous ultrasonographic examination of the uterus took place to detect the presence of fluid in the uterus. Before and immediately after immunization, the mean (+/-SD) duration of luteal phases (progesterone concentrations > or = 1 ng ml-1) was 16.7 +/- 1.6 (n = 39), 17.8 +/- 1.3 (n = 23) and 16.9 +/- 1.1 (n = 18) days in animals of group I, CI and C respectively. Ten goats of group I developed an antibody titre. Persistence of luteal function (mean duration +/-SD: 150.3 +/- 23.5 days) occurred in 6 of these animals and in 1 goat of group CI. Accumulation of fluid in the uterus in group I was first observed between day 31 and 38 of the prolonged luteal phase. Discharge of uterine fluid occurred as soon as the plasma progesterone concentration reached a level lower than 0.5 ng ml-1. It is concluded that immunization against PGF2 alpha is an effective method to induce pseudopregnancy in goats, providing a model for studies on luteal maintenance and uterine function in the absence of a conceptus.