Monitoring ovarian function and pregnancy in the giant panda (Ailuropoda melanoleuca) by evaluating urinary bioactive FSH and steroid metabolites

Urinary excretion of oestrone conjugates, pregnanediol-3α-glucuronide (PdG) and 20α-hydroxypregn-4-en-3-one were measured from 8 weeks before oestrus to 2 weeks post partum and bioactive FSH was monitored during the periovulatory interval in a female giant panda. A biphasic urinary bioactive FSH excretory profile appeared to indicate a broad (~10 day) follicular phase followed by a sharp preovulatory bioactive FSH surge coincident with an acute increase in urinary oestrone conjugates and behavioural oestrus. Weekly concentrations of urinary oestrone conjugates and PdG increased (P<0.001) by Week 9 of gestation with 20α-hydroxypregn-4-en-3-one levels increasing 10-30-fold (P<0.001) between Weeks 11 and 14. These observations indicate that the monoestrous giant panda does not appear to require a prolonged period of endogenous FSH release or multiple FSH peaks for ovarian priming and follicle selection to proceed normally. Furthermore, the delayed rise in urinary steroid excretion during the second half of gestation in the giant panda supports the concept of delayed implantation while the estimation of steroid conjugates in urine offers a non-invasive approach for monitoring pregnancy status in this endangered species.