Bertschinger, H.J., 1994. Reproduction in black and white rhinos: a review: pp. 155-161, fig.1
 | In: Penzhorn, B.L. et al. Proceedings of a symposium on rhinos as game ranch animals. Onderstepoort, Republic of South Africa, 9-10 September 1994: pp. i-iv, 1-242 |
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| Location: |
World |
| Subject: |
Reproduction - Management methods |
| Species: |
All Rhino Species |
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Faecal and urine steroid hormone assays. The most exciting development with regard to the monitoring of wildlife reproduction has been the introduction of faecal and urine steroid hormone assays. This non-invasive approach allows accurate monitoring of the reproductive status of animals, as long as the correct oestrogen and progestagen metabolises are selected for monitoring a particular species. By collecting samples from individual animals at regular intervals, steroid hormone profiles (oestrogens and progestagens), can be obtained, which are then used to monitor the oestrous cycle, pregnancy (including pregnancy diagnosis), parturition and post partum cycling.
The use of urinary steroid hormones was first described in black and indian rhinos. Distinct differences are seen in urinary steroids of these two species. For instance, pregnanediol-3-glucoronide (PDG) was not found in the urine of cycling black rhino but was extremely useful for the purpose of pregnancy diagnosis, and the concentrations climbed steadily throughout gestation. In the Indian rhino, however, PDG was useful for monitoring the oestrous cycle as well as for of pregnancy diagnosis from 3 months of gestation onwards, where levels were significantly higher than during the futeal phase of the cycle. Subsequently Hindle and Hodgesr, have studied the metabolism of oestradiol-17 and progesterone in the white rhino and have identified the main metabolises in urine and faeces.
Monitoring by means of urine and faecal steroids
Oestrus cycle
The first paper dealing with this subject in black rhinos was published by Ramsey et al. They determined oestrogen and PDG concentrations in the urine of cycling and pregnant animals. In order to standardise results, concentrations were expressed relative to creatinine urine concentrations. All subsequent papers dealing with urinary steroids, use the same method of standardisation. Oestradiol and oestrone concentrations did not vary during the oestrous cycle or pregnancy and were found to be of no use for monitoring these events. The same was true for PDG during the oestrous cycle.
Hindle et al. published the next paper on urinary steroids in cycling black rhinos. They identified oestrone and 20 -DHP as the major urinary steroids in 4 cycling cows. A total of nine cycles were monitored and the results showed a follicular phase lasting 3-4 days, a luteal phase of 1 8 days, giving a total cycle length of 21-22 days, which is within the range established by means of observation at Zurich Zoo.
A third paper by Schwarzenberger et al. reported on the faecal progestagen metabolises of cycling and pregnant black rhinos. Two cows monitored for 5 and 6 consecutive cycles had average cycle lengths of 24 and 26,5 days, respectively.
Pregnancy
Ramsey et al. showed that urinary PDG levels could be used to diagnose and monitor pregnancy in black rhinos. In the 8 cows monitored, urinary concentrations were detectable 9-12 months prior to parturition. An interesting finding during one of the pregnancies monitored was the breeding dates of the cow. She was mated on days 493, 467, 460 and 389 before parturition. If one takes the mean gestation period of 464 days observed in Zurich Zoo', it indicates that this cow allowed service during pregnancy (Day 389). The mean length of gestation in this paper is given as 462 days.
Schwarzenberger et al, who monitored pregnancy in 3 black rhino cows by means of faecal progestagens, found a gestation lengths of 440-454, 459 and 470 days, respectively. Mating in the case of the first cow was not observed and, if one takes other reliable sources in the literature into account, it seems likely that this figure cannot be regarded as correct. All 3 cows gave birth to live female calves. From 10 days after rhating and until 2 months of pregnancy faecal progestagens remained at cyclic luteal-phase levels. They then rose further to reach a second plateaux at 4 to 5 months of pregnancy, where they remained until about 2 weeks prior to partus, when they declined. The secondary rise in progestagens during pregnancy was thought to be due to the onset of placental progestagen production. Figure 1 shows the typical profile of 20 -DHP during pregnancy in a black rhino cow.
An interesting additional finding in the work of Schwarzenberger et al., was the fact that all 3 cows showed luteal-phase faecal progestagen concentrations within a month of calving, indicating that the cows had ovulated soon after parturition. Mating, however, was not allowed until the normal time post partum reported for black rhino.
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Reproduction in black and white rhinos: a review
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