Abstract. The progesterone (P4) profiles and macroscopic vulvar changes of female Malayan tapirs were investigated in order to understand their fundamental reproductive physiology and to search for visual indicators of estrus. Blood was collected once or twice a week from seven female Malayan tapirs kept at four zoos. Serum or plasma P4 concentrations were determined by radioimmunoassay. The P4 concentrations changed cyclically throughout the years, and a total of 56 cycles was confirmed in the seven females. The length of the estrous cycle based on the P4 profiles was 43.6 ± 2.0 days; however, this mean includes great variation in length, from 21 to 84 days. Mucous discharge from the vulva and vulvar swelling were seen when the P4 concentrations were low before the beginning of a rise in most cases. In conclusion, captive female Malayan tapirs have variations of approximately 1 to 3 months in estrous cycle length, and visual changes in the vulva are helpful in estimating estrus in female Malayan tapirs.

ABSTRACT. The effects of the long-acting prostagrandin F 2α -analogue fenprostalene were investigated. Twenty-three female beagles (24 cases) 1-6 years of age were divided into 6 groups, and a dose of 5-150 µg/head of fenprostalene was subcutaneously administered at 25 days after ovulation to investigate its effects based on peripheral blood progesterone (P 4 ) levels. The dogs were also examined for shortening of their estrous cycle after administration and fecundity after the recurrence of estrus. The results showed that the administration of 50 µg/head of fenprostalene or more reduced the levels of peripheral blood P 4 to about 1 ng/ml 2 days after administration, indicating early regression of the corpus luteum, and that the administration of these doses shortened the time to the subsequent estrus by a mean of about 80 days, and that conception rates were normal if estrus recurred about 2 months after fenprostalene administration or later.

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ABSTRACT. A long-acting prostaglandin F 2α analogue, fenprostalene, was subcutaneously administered singly at doses of 5, 10, 25, 50, 100 or 150 µg on day 25 after ovulation during pregnancy in bitches (n=4 for each dosage), and maintenance of pregnancy, changes in plasma progesterone concentration, interval between the treatment and subsequent estrus and conception rate at that estrus were studied. Abortion was associated with a decrease in the plasma progesterone concentration below about 2 ng/ml, and the abortifacient effect was dose-dependent. Administration of 50 µg or more of fenprostalene induced abortion in all dogs 3 to 13 days after the treatment. The interval between administration and subsequent estrus was markedly shorter in the aborted bitches than in the non-aborted ones ( P<0.01). The conception rate at the estrus in the aborted dogs was 50%, whereas all of the bitches who had not aborted became pregnant. The results indicate that a single administration of fenprostalene could induce abortion during mid-pregnancy in bitches, and the subsequent estrus may come early with a low conception rate.