Rhino Husbandry Manual
White Rhinoceros
Nutrition
Many of the health problems identified in captive rhinos are believe by some to be linked to nutritional factors. Rhinos consume a large number of species of plants with a diverse array of physical characteristics and nutrients. They represent a range of feeding strategies and, consequently, diet, from browsers (or selective feeders) to unselective grazers. Diets in the zoological setting may have possible imbalances in dietary fats (particularly essential fatty acids) and soluble and insoluble carbohydrates, as well as minerals and vitamins for some species. This chapter outlines current dietary information for maintaining rhinos in captivity and includes a section on hand-rearing
Nutritional Requirements
Due to similarities in digestive tract morphology, the domestic horse still represents the best nutritional model for all rhinoceros species (Clauss et al., 2006a,b). Until further information is obtained, diets should be formulated using current National Research Council (NRC; 2007) recommendations for horses of various physiological stages. Minimum nutrient requirements are listed in Table 2.18
Good quality forages should provide primary nutrients for all herbivores, with concentrate feeds used to balance energy, protein, mineral or vitamin needs. Hay storage is particularly important for ensuring proper dietary management. Moldy or dusty hay may cause colic and/ or heaves. Large amounts of poor-quality hay should not be fed to rhinos, as it may be so poorly digested that impaction and/or colic will result. Very high-quality legume or small-grain hay may be so readily digested that when fed with concentrates, loose feces or colic may result. Browsing species should be fed mixed grass-legume hays and/or a mixture of legume hay and less digestible browse. Alfalfa hay contains more iron than grass hays and should not be fed as the sole forage to black rhinos. Animals should have ad libitum access to hay, water, and salt (Clauss et al., 2006b). The concentrate portion of the ration should be given in at least two feedings daily for better utilization. When practical, a small feeding of hay should be encouraged prior to each concentrate feeding.
In studies of intake, digestion and passage in zoo herbivores, Foose (1982) measured dry matter intakes of approximately 1% of body mass when black rhinos (n=3) were fed grass hays and slightly higher levels (1.2-1.6% of body mass) when fed alfalfa hay. Diets were 43% digestible (black rhinos eating grass). Thus, a guideline for as-fed diet quantity would be approximately 1.5% of body mass. Later studies confirm these earlier data (Clauss et al., 2006a). Smaller pellets can be readily manipulated by browsing species.
​
Animals can sometimes be encouraged to consume less palatable forages if hays are soaked in water or sprinkled with molasses. Applesauce has proved to be helpful in administering unpalatable medications and/or supplements.
​
Produce generally is not offered to white rhinos in their daily diets (indeed, 15/28 institutions do not offer any at all), but some institutions do feed up to 2.3 kg of produce daily. Produce items that are fed for enrichment, training, or as part of a daily diet are listed below (Table 2.19). Similarly, browse generally is not offered to white rhinos in their daily diets (16/28 institutions do not offer any). Where it is offered, a few kg of browse might be offered a few times per year up to free choice when the particular forage is growing (Table 2.19). Browse, excluding grasses and legumes, should not be offered as it is not part of their natural diet. (Cseplo; 2023) The most common hays and concentrated pellets fed among white rhinos are noted below (Table 2.19). Hay is often fed in variable amounts, from 0 kg to ad libitum, depending on the available grazing. Two of the surveyed institutions do not feed any pellets. It is important to remember that all diets should be based on forages, not concentrates.
​
Feeding Location
As with all zoo species, feed should be offered on a concrete pad or in livestock troughs or bins. Sand impaction has previously been documented in rhinos (Nouvel and Pasquier, 1946); therefore, feeding directly on the ground is not recommended. To reduce competition for food, individual feeding stations or adequate space at communal feeders is recommended.
Supplements
Dietary supplements should be unnecessary in properly formulated rations. A vitamin-E deficiency has been documented in zoo-housed black rhinos (Clauss et al., 2002); current recommendations based on natural browse composition (Dierenfeld et al., 1995) suggest that diets should contain 150 to 200 IU vitamin E/kg dry matter. Salt blocks and water should be available at all times. If grown in an area prone to soil selenium (Se) deficiency, forage should be tested routinely for determination of Se content in order to provide data needed for balancing rations (Table 3.19).
Problematic Diets
Alfalfa hay as an exclusive forage may lead to iron storage issues and mineral imbalances, and high-quality alfalfa may lead to colic and diarrhea. The consumption of fresh red maple browse has been associated with hemolytic anemia in horses and should therefore be avoided.
Browse
Particularly for the browsing rhino species, the addition of fresh and/or frozen browse may be essential to dietary health. Browse may contribute required nutrients that have not yet been quantified and may also be of benefit to dilute a captive diet that is too digestible. Table 3.20 lists North American browse species currently fed to black rhinos
Hand-Rearing
A limited number of rhino calves have been and are currently being raised using various formulas. Reports and published information must be carefully scrutinized for measures of success and methodology in milk-sample analysis. The following information uses the ungulate hand-rearing chapter in the AZA Infant Diet Notebook as a base for general feeding guidelines and formula selection (Reiter et al., 1994). This recommendation is to be used as a guideline for standardization of a hand-rearing diet.
Milk Composition and Formula Selection
Based on available data, rhinoceros milk is more dilute than milks of other ungulate species. It is low in solids, low in protein, very low in fat and high in sugar compared with milk of equids, bovids and cervids (Oftedal, 1984). Formula selected should mimic mother’s milk in composition as much as possible (Table 3.21). In Table 3.22, Formula One has been used to raise a calf to one year of age; Formula Two more closely mimics mother’s milk. In Europe, Mazuri® makes a rhino milk replacer for black rhinos (www.mazuri.eu). Land O’Lakes® Mare’s Match® (Table 3.23) has been used to supplement a greater one-horned rhino calf at San Diego Zoo Safari Park and possibly could be used for hand-raising black rhino calves (powder:H2O = 1:6 but formula may need to be mixed at a more dilute ratio (1:8) for the first few days to avoid problems with constipation). The San Diego Zoo Safari Park has used a low fat cow’s milk: nonfat cow’s milk: lactose powder: water (27:9:1:1 by weight)(Blakeslee and Zuba, 2002).
Though rhinoceros’ milk is different from cow’s milk, the latter may still be appropriate for hand-rearing rhinos if used in combination with other ingredients. Cow’s milk is low in iron; consequently, an iron source such as Fer-In-Sol® (Table 3.23) should be added to the formula at two drops per 100 g of formula. In addition, infant vitamins, such as Major® Multi-Vita Drops® (Table 3.23), should also be added to the formula at two drops per 100g of formula. Some infant vitamins, such as Mead Johnson® Poly-Vi-Sol with Iron® (Table 3.23), contain added iron. San Diego Zoo Safari Park uses Probios® (2 tbsp) and Lixotinic® (0.44 ml /kg body weight)(Table 3.23) as daily supplements added in the first bottle. The animal may also benefit from the addition of Lactaid® at one drop per 100 g of formula. Lactaid® (Table 3.23) aids in carbohydrate digestion and helps prevent possible gastrointestinal tract distress. If the neonate is less than 24 hours old, colostrum diluted 50% with water or an electrolyte solution for ungulates, such as Replenish® (Table 3.23), should be administered for the first 24 hours. Though species-specific colostrum is preferred, cow colostrum may be used. San Diego Zoo Safari Park uses Land O’Lakes® Colostrum Replacement® (Table 3.23) in the first 24 hours after nursing followed by a mix of 50% colostrum and 50% formula during the next 24 hours, and then 100% formula until weaning. Products such as Colostrx®and Seramune® Oral may also be used (Table 3.23). To avoid gastrointestinal distress, a diluted formula should be offered beginning on day two. The formula can be gradually increased to full concentration depending on the animal’s health, including weight gain and stool condition. Prior to feeding, the formula should be warmed to approximately 37°C (99°F). Rhinoceros calves prefer their milk cooler than many other ungulates.
Feeding Regimen
The calf should be stabilized and hydrated before any feeding. Quantity fed should range from 10 to 13% of body weight (BW). Animals should be fed every two hours. Because infants suckle during daylight hours, feeding should be equally spaced in a 12-hour period not to exceed 3 to 4% of body weight at any one feeding. It is recommended that feeding begin with 10% of body weight split equally into 12 feeds one hour apart during daylight hours. The quantity of formula fed should be adjusted daily based on the animal’s weight. Animals should be weighed at the same time each day. Fresh water should be available at all times.
If diarrhea occurs, the quantity of formula fed should be decreased or the formula diluted until stool condition returns to normal. If diarrhea is persistent, an electrolyte solution can be used to dilute the formula, replacing some or all of the water. In addition, the number of feedings can be increased to lessen the quantity fed at any one time. Formula can be prepared ahead of time and warmed as needed. Water should be boiled to decrease possible contamination due to pathogens and refrigerated before being added to the formula. The formula should be refrigerated and used within 72 hours. Prior to feeding, the formula should be warmed to the animal’s body temperature. Calf nipples work well with large species. Bottles should be boiled before use. Diluted bleach may be used as a disinfectant. Formula left over from each feed should be discarded.
​
Weaning
Weaning may begin as early as six months if necessary and should be completed in one year. Weaning is a slow process involving carefully monitoring of body weight and solid food consumption. Animals should have access to solid food at all times. A nutritionally complete pellet diet such as Calf Manna (Manna Pro Products, LLC., Chesterfield, MO, USA), horse feeds or high fiber ungulate pellets, in addition to high-quality grass hay, is appropriate. Formula may be decreased by gradually eliminating the number of feeds or decreasing the amount offered per feed and gradually decreasing the number of feeds
Table 3.24 Example Feeding Regimen (San Diego Zoo Safari Park)
Week 1 & 2
Week 3 & 4
Week 5 & 6
Week 7 & 8
Week 9 - 14
Week 15
Week 15 - 30
Week 30 - 40
Week 41
Week 52
Week 60
​
6am, 8, 10, 12, 2, 4, 6, 8pm
6am, 8, 10, 12, 2, 4, 6pm
6am, 8, 10:30, 1, 3:30, 6pm
6am, 9, 12, 3, 6pm
6am, 10, 2, 6pm
No more increases to daily volume.
6am, 12, 6pm
6am, 12, 6pm
6am, 12, 6pm
Start dropping amount on all bottles.
Weaned.
(18-20% BW) 8 feedings
(17-19% BW) 7 feedings
(16-18% BW) 6 feedings
(14-16% BW) 5 feedings
(12-14% BW) 4 feedings
​
(8-12% BW) 3 feedings
(5-7% BW)
(3-4% BW)