Urinary steroid concentrations during natural and gonadotrophin-induced oestrus and pregnancy in the giant panda (Ailuropoda melanoleuca)

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Abstract
Urinary concentrations of conjugated oestrone and pregnanediol-3-glucuronide were measured during and after spontaneous and induced oestrus and during pregnancy. Behavioural oestrus was preceded by a rise in oestrone values from < 10 ng/mg creatinine (Cr) to peaks of 45 ng/mg CR. Maximal lordotic response and mating activity coincided with the decline in oestrone levels. After presumed ovulation, urinary pregnanediol glucuronide concentrations increased from < 5 to 15-30 ng/mg Cr. Further increases in this steroid (to 60-80 ng/mg Cr) occurred 114 days after mating, presumably coincident with implantation. These high levels of pregnanediol glucuronide were maintained for 3 weeks, began to decline 1 week before parturition and fell to a nadir (< 5 ng/mg Cr) immediately after delivery. When FSH was administered i.m. for 5 days, urinary oestrone values rose markedly and were maximal (580 ng/mg Cr) on Day 7. Mating first occurred on Day 20 and 500 i.u. hCG were given i.m. Urinary pregnanediol glucuronide levels during the next 5 months were similar to those in the previous year during pregnancy with values rising 105-108 days after mating. However, no birth occurred. These results support the suggestion that pandas exhibit delayed implantation and demonstrate that the panda is responsive to exogenous gonadotrophins. [The giant panda is an endangered species, numbers of which in the wild are decreasing at an alarming rate. Therefore, great efforts should be made to learn enough about the reproductive biology of this animal to assure successful breeding in captivity.].