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Nutrition in Subungulates and Ungulates

By Joeke Nijboer, PhD, Rotterdam Zoo

Hay comprises the bulk of the diet for most ungulates in captivity and should be available for most of the day rather than fed at intervals as meals. In general, a leafy legume hay, eg, alfalfa, should be used for species that are primarily browsers (eg, Giraffidae, Cervidae, sitatunga, bongo, duiker, tapir), whereas a good-quality grass hay is satisfactory for most grazers or bulk feeders (eg, zebra, elephant, bison, buffalo, wildebeest, camel). Legume hays are higher in nitrogen and calcium and, if of good quality, are more digestible than grass hays. Hay should be leafy and green, free of mold, dirt, excess weeds, and other foreign matter, and should not be overmature. Several zoos are test-feeding hay and alfalfa silage. In general, palatability is good.

Hay analysis can be very useful to evaluate quality and design proper feeding programs. “Poor” hay will have a good fiber percentage, but the protein quality can be low and poor, and the mineral status, especially of calcium, can be too low. Low levels of calcium can cause poor bone calcification and also affect the calcium level in the blood, which can cause birth problems.

Precautions should be taken if feeding silage products. If the silage was not processed or stored properly or contaminated by animal or meat products, it may contain fungi or bacteria (eg, Clostridium botulinum) that can produce lethal toxins.

In addition to hay, a pelleted diet that contains protein, minerals, and vitamins in concentrations adequate to meet the needs of domestic species and those wild species for which data are available (eg, white-tailed deer) should be offered. See table: Diets of Selected Mammals for composition of a sample pellet for large herbivores. In the frequent situation in which animals are fed as a group rather than as individuals, it is preferable to use a pelleted diet that is not excessively high in digestible energy (~3 kcal DE/g dry matter is suggested) and that contains sufficient fiber to support proper rumen or colon function. This precaution reduces the possibility of untoward effects (eg, rumen acidosis, colic, obesity) caused by overconsumption of concentrates. Depending on the nutritional status of the animal, ~0.5–1.5 kg should be fed per animal. Overfeeding can result in obesity. Animals should be weighed regularly, or body condition scoring performed.

A specialized pellet with high amounts of neutral detergent fiber (NDF) and acid detergent fiber (ADF) is recommended for browsers (eg, giraffe, kudu, okapi, reindeer), and a pellet with moderate amounts of NDF and ADF is recommended for grazers (eg, elephant, bison, banteng, addax antelope). The intermediate feeding animals should get an equal mix of the browser and grazer pellets. Preferably, the diet of browsers should consist of equal parts of browser pellets, good palatable alfalfa, and browse. Diets for grazers and browsers should contain high amounts of vitamin E and biotin to prevent muscle dystrophy and hoof problems.

A pellet size of 3/16 in. is satisfactory for most artiodactyls, whereas a pellet or cube size of ½ in. (~13 mm) helps minimize waste when fed to larger perissodactyls and subungulates. Commercial cattle products should not be fed to zoo herbivores because of palatability problems and low vitamin E levels, and some products may contain nonprotein nitrogen sources such as urea that are not tolerated by hindgut-fermenting species (eg, equids). Also, the amount of easily digestible energy may be high, leading to obesity. Tapirs should get a mixture of grazer and browser pellets combined with some greens, alfalfa, and browse.

In general, most large ungulates (>250 kg) consume 1.5%–2% of their weight in dry matter daily. Smaller species (<250 kg) generally consume 2%–4%. Offering a pelleted diet at 10%–15% of the dry-matter intake is adequate for most grazers if good-quality hay is fed. The amount of minerals and vitamins should be balanced in the pellets in such a way that the total diet (including greens, browse, and hay) should be adequate. When hay quality declines, or for more delicate species, the percentage of high-fiber pellets should be increased. Ungulates and subungulates should always have salt blocks available, preferably with a balanced vitamin and mineral supplement. However, excessive licking can become a neurotic behavior and should be prevented.

Elephants should receive extra calcium, because mostly poor hay with a low level of calcium is fed. Because of the sensitivity to hemosiderosis, black rhinos should be fed a diet with a low level of iron (<100 mg/kg dry matter). Browse can contain significant amounts of iron; however, rose leaves contain low amounts. It is speculated that other ungulate species may also get hemosiderosis. It is advised that all ungulates be exposed to UVB from sunlight, because it has been suggested that oral supplementation of vitamin D in some cases is not sufficient (elephant, kudu).

Hay should be fed from a rack rather than off the ground for most species (elephants are an exception). Hay racks should be located at eye level for tall browsers such as giraffes and gerenuks. Pellets can be offered from a covered trough or (rubber) feed pans. Regularly feeding the pelleted diet in an animal’s holding area can facilitate close observation and easy capture. If possible, animals should be fed separately to ensure that each individual receives a similar amount of food. If feeding separately is not possible, at least two widely separated feeding stations may be necessary to reduce conflict and to ensure that subordinate animals obtain their share of food.

In addition to hay and pelleted diet, assorted fruits and vegetables often are fed to exotic ungulates. For most species, these items usually are not necessary except as an occasional treat; the amount should be limited to <10% of the total diet. The exception might be for those species that regularly feed on fruits and succulents in the wild. It may be advisable to include some greens and vegetables (~0.5 kg/100 kg body wt) in the diet of species such as okapi, duikers, dik diks, bongo, and tapirs. Fresh, frozen, or dried browse is consumed avidly by most captive ungulates and subungulates and should be offered to browsers if possible ad lib, because it improves rumen function.