Abstract

Introduction

White rhinoceros are generally classified as hind-gut grazers. Wild diets typically consist of grasses with some low-lying vegetation occasionally taken. In captivity, it is common to supplement commercially available hay with a pelleted concentrate. While generally hardy animals once acclimated to captivity, the lack of reproductive success prompted the staff at Busch Gardens Tampa Bay (BGT) to start investigating the possible role of nutrition in the lack of the F1 generation of white rhinoceros to breed successfully in captivity.

Methods and Materials

In May 2001, 1.2 white rhinoceros estimated at 5 years of age, arrived at Busch Gardens Tampa Bay (BGT) from the Kruger National Park. After their capture they were held in bomas and adjusted to a diet of local grass hay for 6 months prior to their arrival in Busch Gardens. Upon arrival to Florida, they were housed together in a sand pen and fed a combination of timothy and alfalfa hays. The rhinoceros were trained within a few months for voluntary blood draws from the caudal surface of the ear and to stand on a platform for weights. A 5-day intake study was conducted in March 2003 prior to their relocation to a 15-acre mixed species display. Serum was stored and retrospectively analyzed for vitamin and mineral levels. Routine serum blood chemistries and complete blood cell counts were also examined periodically. Once moved, obtaining weights became routine. Two pregnancies have been confirmed and monitored. Milk was collected but was not analyzed for nutritional content as of this writing. A growth curve for the offspring has been established.

Results

The results of the intake study are summarized in Table 1. The three rhinoceros were treated as one individual and the totals summed per the protocol. Table 2 shows the weights of the adult rhinoceros. The first weight in October 2000 was at capture in Kruger National Park. Figure 1 shows the growth curve of the first calf born to female 61409. This calf averaged approximately 1.5 kg per day growth during the first year of life. Table 3 shows the most recent vitamin and mineral serum analysis of the four rhinoceros on the forage-only diet.

Table 1. Five-day intake study of one male and two female white rhinoceros at Busch Gardens Tampa Bay. All weights are in pounds

Table 2. Weights (kg) of three adult white rhinoceros managed on forage-only diets at Busch Gardens Tampa Bay

Figure 1 Growth curve of female calf 62638. Date of birth: 12 October 2004

Table 3. Representative vitamin and mineral profile of white rhinoceros at Busch Gardens Tampa Bay on forage diets

Discussion

Alfalfa hay was limit fed and the rhinoceros always consumed it all. It was fed at the same time and is a preferred item over the timothy hay. The intake of 1.2% should be a good estimate as the rhinoceros still had plenty of palatable hay to consume if they chose. This figure represents a combination of timothy and alfalfa hay intake. Foose reports separate intake for grass hay (1.03%) and alfalfa hay (1.19%).³ Feeding 100% alfalfa is not advisable and was not looked at in this project. The combination hays fed here led to a similar intake of alfalfa by Foose and avoided the potential complications of feeding alfalfa exclusively to herbivores. The weight gains by the adults appeared reasonable and their overall condition is excellent (M. Hoftmyer 2006 pers. comm.). The growth curve of the young female calf, 62638, shows a steady weight gain. This provides good evidence that the energy status of the dam was adequate. This female did lose some weight during this lactation period but her condition remained good and she has already conceived again. It can also be inferred that the protein level was adequate in this growing calf.

The only complications encountered so far have involved minerals. Table 3 compares the most recent serum vitamin and mineral analysis to published levels in free-ranging white rhinoceros. The zinc level was low in all animals and especially in 61409, the female with the calf. While lactating, this female developed a depigmentation of the skin on the withers. Biopsy revealed hyperplastic lesions consistent with zinc deficiency in domestic cattle.⁴ The zinc level at this time was 0.57 µg/dl with a reference level of 1.39 ± 0.2 µg/dl.¹ Several browse and forages were looked at for zinc content and Spanish moss (Tillandsia usneoides) was chosen as a supplement. It is highly palatable and has a high level of zinc. High calcium diets also may lower zinc by competitive binding in the gastrointestinal tract.⁴ The amount of alfalfa was reduced to its current level and is now used only for husbandry and medical procedures. The serum zinc level improved as did the skin condition over several weeks. The reduction in calcium intake is believed to have been more useful as the supply of Spanish moss was exhausted soon. Other vitamin and minerals were within the range reported in wild rhinoceros with the exception of the iron in the calf 62638. The iron level at 12 months of age was 1.59 ug/dl, well within the reference range. At 16 months of age it had dropped to 0.89 µg/dl. This calf has no other health problems at this point but this aspect will be closely followed on the premise that this drop in iron is due to weaning.

With the notable exception of zinc, it appears that white rhinoceros can be successfully maintained and propagate on a forage-only diet. If this trend holds true it is hoped the F1 generation produced will be fed the same way. The addition of concentrates and commercial feed stuffs may be affecting reproduction possibly as an antigenic source and will be investigated. Close attention should be paid to all nutrients when conducting such trials. The emphasis on operant conditioning cannot be underestimated in this trail.

Reprinted with permission of the Comparative Nutrition Society (CNS). 2006. Proceedings of the Sixth Biennial Conference, Keystone, Colorado. Information in the CNS abstracts is not peer reviewed and cannot be considered endorsed by the society.

Literature Cited

1.  Clauss M, Jessup D, Norkus EB, et al. Fat soluble vitamins in the blood and tissues of free-ranging and captive rhinoceros. J Wildl Dis. 2002;38(2):402–413.

2.  Dierenfeld ES, Atksinson S, Craig AM. Mineral concentrations in serum and liver tissue of captive and free-ranging rhinoceros species. Zoo Biol. 2005;24:51–72.

3.  Foose T. Trophic Strategies of ruminant versus nonruminant ungulates. PhD dissertation University of Chicago. 1982:163–164.

4.  Miller WH. Nutritional, endocrine, and keratinization abnormalities. In: Howard JL, ed. Current Veterinary Therapy 3 Food Animal Practice. Philadelphia, PA: W.B. Saunders Co.; 1993:912.