Home > Our Research > Projects: Sumatran Rhino Report

2. Ultrasound as a tool for early pregnancy detection and loss

Early pregnancy detection

Post-breeding ultrasound will provide essential information in order to efficiently manage captive rhinos. Pregnant animals can be separated from males to reduce stress and prevent the inadvertent breeding of pregnant animals which may contribute to pregnancy loss.

Early embryo loss

The early embryonic vesicle in the rhinoceros resembles the horse (Radcliffe et. al., 2001; Roth et. Al., 2001). The early vesicle can be imaged as early as 14 days post-breeding and its documentation is critical, especially if embryo loss ensues. Without ultrasound the only indication that pregnancy occurred would be an extension of the luteal phase. As previously evidenced in the Sumatran rhino, embryo and fetal loss can be a significant cause of infertility. Perhaps the Sumatran rhino is very susceptible to captive stresses that result in reduced fertility in captive animals — a fact supported by their solitary forest nature and apparent infrequent encounters with other rhinos (particularly males) except during the short period of receptivity and copulation.

3. Ultrasound as a tool to assess reproductive pathology and guide therapy

Captive Sumatran rhinos appear to develop significant reproductive pathology with increasing nonparous time in captivity. The information of reproductive health is critical to dedicating appropriate resources, time and concentration of efforts toward normal animals. Appropriate therapeutic steps can be guided by monitoring reproductive function with ultrasound in concert with other medical testing.

Suggested Guidelines for Ultrasonographic Monitoring of Sumatran Rhino

1) Schedule for ultrasound evaluation of Sumatran rhino estrous cycle,

Ultrasound can used in conjunction with serum progesterone assay to precisely time male and female introductions for breeding. The serum P4 assay may be used to predict female receptivity and guide the timing of ultrasound exams for more precise determinations of timing as needed. As illustrated above, initiation of ultrasound evaluation at approximately Day 19 of 21 day cycle could be used to critically evaluate follicular size and predict impending estrus, especially in problem females where serum P4 assay alone is considered insufficient to guide decisions (this was illustrated nicely with our predicted breeding between Mas Merah and Ara on 29 August 2001).

2) Schedule for ultrasound evaluation of rhinoceros early pregnancy,

Day 15 = earliest detection of embryonic vesicle

• Important stage as early loss can occur between days 15-20 secondary to failure of implantation with return to cycle at 21 days

• May be difficult to differentiate and early embryo from an endometrial cyst (see Rima Figures 1 and 2)

Days 20 — 30 = embryo proper first visible at this stage

• Important to document this stage as this is the time period most likely to see early embryo loss

 

• Embryo loss at this stage most likely will result in prolongation of the luteal phase with elevation of progesterone levels

Days 40+ = beginning of fetal stage

• Fetal loss is much less likely at this stage unless luteal insufficiency develops as with Emi at Cincinatti

• Monthly exams during fetal stage for monitoring of normal fetal health and development

more »

page 32