Abstract
After ovulation, non-pregnant female giant pandas experience pseudopregnancy. During pseudopregnancy, non-pregnant females exhibit physiological and behavioral changes similar to pregnancy. Monitoring hormonal patterns that are usually different in pregnant mammals are not effective at determining pregnancy status in many animals that undergo pseudopregnancy, including the giant panda. Therefore, a physiological test to distinguish between pregnancy and pseudopregnancy in pandas has eluded scientists for decades. We examined other potential markers of pregnancy and found that activity of the acute phase protein ceruloplasmin increases in urine of giant pandas in response to pregnancy. Results indicate that in term pregnancies, levels of active urinary ceruloplasmin were elevated the first week of pregnancy and remain elevated until 20–24 days prior to parturition, while no increase was observed during the luteal phase in known pseudopregnancies. Active ceruloplasmin also increased during ultrasound-confirmed lost pregnancies; however, the pattern was different compared to term pregnancies, particularly during the late luteal phase. In four out of the five additional reproductive cycles included in the current study where females were bred but no birth occurred, active ceruloplasmin in urine increased during the luteal phase. Similar to the known lost pregnancies, the temporal pattern of change in urinary ceruloplasmin during the luteal phase deviated from the term pregnancies suggesting that these cycles may have also been lost pregnancies. Among giant pandas in captivity, it has been presumed that there is a high rate of pregnancy loss and our results are the first to provide evidence supporting this notion.
Highlights
With over 300 pandas in captivity around the world, substantial progress has been made in the ex-situ conservation of this species in recent years, but as with any small population, careful management is required to maintain genetic diversity and to prevent inbreeding [1]
In pregnancies carried to term, the levels of active ceruloplasmin in urine were elevated by 3.2- to 19.8-fold at week one of the luteal phase compared to the levels observed at proestrus/estrus (P#0.05; Figure 2)
The secondary rise in progestagens was calculated for each luteal phase in cycles where breeding or artificial insemination (AI) occurred to determine the relationship between the pattern of ceruloplasmin and progestagens
Summary
With over 300 pandas in captivity around the world, substantial progress has been made in the ex-situ (captive) conservation of this species in recent years, but as with any small population, careful management is required to maintain genetic diversity and to prevent inbreeding [1]. Female giant pandas spontaneously ovulate [2] and undergo a phenomenon known as pseudopregnancy if not pregnant, wherein a female’s reproductive hormones are similar in concentration and length during the nonpregnant luteal phase as during pregnancy. This makes pregnancy determination impossible by diagnostic hormonal tests typically used in other mammals [2,3]. The primary rise of progestagens is followed by a more consistent secondary phase which comprises a substantial increase in progestagens above baseline lasting 40–50 days [4,5]. In a pregnant giant panda, the embryo remains quiescent in embryonic diapause until the secondary rise of progestagens when implantation is suspected to occur and the fetus begins to grow rapidly [2,3,7,8,9]
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