Macropod Nutrition

Joseph A. Smith, DVM

KEYWORDS

� Macropod � Kangaroo � Wallaby � Joey � Nutrition

Macropods are marsupials belonging to the family Macropodidae and are commonlyreferred to as kangaroos and wallabies. Macropods are frequently kept in zoologicparks and are becoming increasingly more popular as pets and in hobby exhibits.The most common species maintained in captivity in North America are the redkangaroo (Macropus rufus), the Eastern gray kangaroo (M. giganteus), the Westerngray kangaroo (M. fuliginosus), the red-necked/Bennett’s wallaby (M. rufogriseus),the Tammar wallaby (M. eugenii), and the common wallaroo (M. robustus). Otherspecies, such as the Parma wallaby (M. parma), yellow-footed rock wallaby (Petrogalexanthopus), and tree-kangaroos (Dendrolagus spp), are also kept in zoos but arenearly absent in private collections.

Macropods are all herbivorous, but they have evolved to adapt to a wide variety ofhabitats and associated vegetation. Macropods can be loosely grouped into threemain classifications based on dietary preference: (1) primary browsers, (2) primarygrazers, and (3) an intermediate browser/grazer grade.1 In reality, dietary preferenceis more of a spectrum ranging from exclusive browsers to exclusive grazers. Ingeneral, the larger species tend to be primarily grazers, whereas the smaller speciesare primarily browsers. A summary of the dietary classification of various macropodsis provided in Table 1.2

All macropods are foregut fermenters, with most digestion occurring in the stomachby microbial flora. This method of digestion is less dependent on the quality of dietarynitrogen and has the added advantage of being able to degrade plant cell walls toproduce energy and provide access to the plant cellular contents. In general, thismethod allows macropods to use poorer quality forages when compared with otherherbivores with different digestive strategies. Macropod nutrition is fairly well studied,and an excellent comprehensive review has been published.3,4

ANATOMYAND PHYSIOLOGYDentition

Macropods belong to the order Diprotodontia, members of which are characterized bythe presence of two large procumbent (horizontally arranged) mandibular incisors. Themaxillary incisors are much smaller and are found in three pairs. Macropods use theirincisors for prehension of food. Mandibular canines are absent, and maxillary canines

Fort Wayne Children’s Zoo, 3411 Sherman Boulevard, Fort Wayne, IN 46808, USAE-mail address: vet@kidszoo.org

Vet Clin Exot Anim 12 (2009) 197–208doi:10.1016/j.cvex.2009.01.010 vetexotic.theclinics.com1094-9194/09/$ – see front matter ª 2009 Elsevier Inc. All rights reserved.

Table 1Dietary characteristics of macropod species mentioned in the text

Common Name Scientific NameAverageAdultWeight (kg) Diet Classification Wild Diet

Tree-kangaroo Dendrolagus spp 3.7–15.0 Browser Leaves, fruit,flowers, grass

Dorcopsis Dorcopsis sppand Dorcopsulusspp

1.5–11.5 Browser Leaves,flowers,fruit

Hare-wallaby Lagorchestes spp 0.8–4.6 Intermediate Forbs, greengrass, seedheads, fruit

Tammar wallaby Macropuseugenii

4–10 Intermediate Short grass,forbs

Parma wallaby Macropus parma 3.2–5.9 Intermediate Short grass,forbs

Bennett’swallaby

Macropusrufogriseus

11–27 Intermediate Short grass,forbs, bushes

Commonwallaroo

Macropusrobustus

15–21 Grazer Grass, forbs

Red kangaroo Macropus rufus 26–85 Grazer Grass, forbs

Western graykangaroo

Macropusfuliginosus

22–54 Grazer Grass, sedges,shrubs, forbs

Eastern graykangaroo

Macropusgiganteus

26–66 Grazer Grass

Nailtail wallaby Onychogalea spp 4–9 Grazer Forbs, greengrass, fallenleaves

Rock-wallaby Petrogale spp 0.9–7.5 Browser Forbs, younggrass, leaves,woody shrubs,ferns

Quokka Setonixbrachyurus

2.5–5.0 Browser Forbs, shrubs,sedges, grass

Pademelon Thylogale spp 1.8–12.0 Browser Ferns, fallenleaves, shortgrass, fruit

Swamp wallaby Wallabia bicolor 10–20 Browser Sedges, forbs,shrubs, grass,ferns, fungi,seeds

Data from Sanson GD. Morphological adaptations of teeth to diets and feeding in the Macropo-doidea. In: Grigg G, Jarman P, Hume I, editors. Kangaroos, wallabies, and rat-kangaroos. Sydney:Surrey Beatty; 1989. p. 151–68; Dawson TJ. Diets of macropodoid marsupials: general patternsand environmental influences. In: Grigg G, Jarman P, Hume I, editors. Kangaroos, wallabies, andrat-kangaroos. Sydney: Surrey Beatty; 1989. p. 129–42.

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are rare, which results in a relatively long diastema. In adults, a single premolar andfour molars are found in each arcade, all of which are used for mastication. Molarprogression, a specialized adaptation of some macropods whereby older molarsmigrate rostrally, and molar eruption can be used along with species-specific data

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charts to estimate the age of macropods.5 The three different grades of macropodsbased on dietary preference (ie, grazers, browsers, and intermediates) exhibit dentaladaptations that are specific to their preferred food source.

In macropods that are primarily browsers, the first maxillary incisors are larger thanthe others and occlude the mandibular incisors over a relatively small area to allow forprecise prehension of specific plant species or plant parts. The premolars are perma-nent and larger than those of grazers, and they act as an anchor to prevent the molarprogression seen in grazers. The dental arcade is relatively flat, allowing all molars(which remain permanent) to reach occlusion at the same time resulting in a crushingaction.

Species in the intermediate browser/grazer grade still have large first maxillary inci-sors, but the third maxillary incisors are slightly wider to allow for more surface areaduring occlusion to allow cropping of larger quantities of vegetation. The premolaris smaller and therefore less effective at preventing molar progression, which occursin most species in this grade. Molars possess crushing and shearing abilities, whichmakes them adaptable but less efficient at either task.

The Nabarlek (Petrogale concinna) is a member of the intermediate grade withadaptations more like the grazers. This is because the Marsilea spp ferns, whichcomprise a large part of its diet, are high in silicates and cause excessive dentalwear. Adaptations include a markedly reduced premolar, a highly curved dentalarcade, and well-developed molar progression. The Nabarlek is the only marsupialwith an unlimited number of molars, with new molars produced as older ones areshed when worn.1 The banded hare-wallaby (Lagostrophus fasciatus) is also an aber-rant member of the intermediate grade. It has a small premolar with resultant molarprogression, but its dental arcade is flat. Instead of older molars being shed, theyare retained, which results in a progressively shortening diastema.1

Macropods that are primarily grazers have adaptations, including harder enamel,that are targeted at preventing dental wear caused by the higher levels of silicatesin the grasses they eat.6 The first maxillary incisors are relatively small, whereasthe third maxillary incisors are wide, which increases the occlusive contact with themandibular incisors and allows for cropping of larger quantities of forage. Thepremolar is vestigial and allows for molar progression. The dental arcade is highlycurved, resulting in an average of only two molars in occlusion at any given time. Asmolars are worn, molar progression allows newer, more caudal molars to enter intoocclusion while worn ones move rostrally and are eventually shed. Morphology of indi-vidual molars of grazers allows for reduced surface contact between teeth, whichresults in efficient shearing forces during mastication, as opposed to the crushingforces of browsers, which result in more wear.

Salivary Glands

Macropods possess three main groups of salivary glands. The parotid glands are thelargest, followed by the mandibular glands, with the sublingual glands being thesmallest.7 The composition of saliva fromeach group of glands is different. Parotid salivais high in sodium, calcium, phosphate, and bicarbonate. Phosphate and bicarbonateare important in buffering the short-chain fatty acids produced in the forestomach byfermentation.8,9 Phosphates from saliva also serve as a source of phosphorus forbacteria in the forestomach. In contrast, mandibular gland saliva is low in phosphateand bicarbonate, making it less useful as a buffer. Instead, it is composed of a hypotonicsolution of sodium chloride and potassium chloride, which results in less electrolyte losswhen this saliva is spread onto the forearms in a unique adaptation that allows forevaporative cooling during times of hyperthermia or stress.10

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Esophagus

The esophagus is lined by stratified epithelium with no glands. Except in tree-kanga-roos, the macropod esophagus has a well-keratinized epithelial layer. The morphologyof the macropod esophagus has been classified into four main types.11 Type I hasa smooth lining and is found in the browsing and intermediate grade groups: rock-wallabies (Petrogale spp), tree-kangaroos, pademelons (Thylogale spp), nailtailwallabies (Onychogalea spp), hare-wallabies (Lagorchestes spp), dorcopsis (Dorcop-sis spp and Dorcopsulus spp), and the Quokka (Setonix brachyurus). The Type IIesophagus has a smooth lining with large irregular longitudinal folds. This type is foundin the large grazing species within the genus Macropus. The Type III esophagus islined with finger-like papillae and is found in smaller wallabies within the genus Macro-pus and in swamp wallabies (Wallabia bicolor). The Type IV esophagus has longitu-dinal folds cranial to the diaphragm and papillae caudal to the diaphragm and isfound in Bennett’s wallabies. Esophageal nematode species with specialized confor-mations adapted to keep them anchored near the esophageal lining have beendescribed.12 Esophageal bacterial flora also have adaptations such as extracellularcoats and capsules for attaching to the surface epithelium, on which they only colonizethe superficial layers.13

Stomach

The stomach of macropods can be divided into two main regions: the forestomachand the hindstomach. The forestomach is an expansion of the cardiac region of thestomach and is the primary site of fermentation. The forestomach can be dividedinto sacciform and tubiform regions, which are separated by a ventral fold (Fig. 1).In general, the smaller species have relatively larger sacciform regions comparedwith larger macropods. Exceptions include the hare-wallabies, which have a more tu-biform forestomach. Histologically, the forestomach contains regions of squamousepithelium and cardiac glandular mucosa. The amount and location of each tissuetype varies widely with species. The cardiac mucosa has mucin-secreting glandsand little enzymatic activity. Three taenia are present in the forestomach, resulting innumerous haustrations, the pattern of which varies with species.

The hindstomach is the site of digestive enzyme production. The gastric glandularregion appears rugose and reddish in color. Histologically it is a typical gastric epithe-lium. Pyloric glands similar to the mucin-secreting glands in the cardiac glandularmucosa are also present. A gastric sulcus that connects the esophagus and the hind-stomach exists in some species, but the morphology can vary. In pouch young,proteolytic activity exists throughout the stomach, so the presence of a sulcus is prob-ably of little benefit in this age group.14 The sulcus may be an adaptation that benefitsjoeys-at-foot (ie, those that are out of the pouch and beginning to eat solid foods butstill nursing periodically). The sulcus also may aid digestion in adult macropods bymoving more liquid products of fermentation caudally toward the hindstomach.15

Two types of contractions have been described in macropod stomachs.15 The firsttype is localized contractions that function to aid mixing of digesta. The second type isa sequential wave of contractions that propulses digesta caudally. Unlike the rumen,which acts like a large fermentation vat in which ingesta is mixed throughout, the for-estomach of macropods mixes ingesta within localized pockets with an overall tubularflow of ingesta caudally.

The fauna and flora of the macropod forestomach is diverse. In wild macropods, thebiomass of helminths has been described as larger than that of microbes.3 Helminthfauna consists of anoplocephalid cestodes, strongyloids, trichostrongyloids,

Fig.1. A typical macropod digestive tract using the Eastern gray kangaroo (Macropus gigan-teus) as a model. (Drawing by V.L. Piebenga.)

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metastrongyloids, oxyurids, and filaroid nematodes.16 Of the strongyloids alone, 40genera and 171 species have been described, with many more still undescribed.The pathogenicity of specific helminth species has not been well researched. Thebacterial flora of the macropod forestomach is morphologically similar to that ofsheep, with similar bacterial densities. The flora is predominantly gram negative, butgram-positive rods become more dominant in regions with lower pH.17 The bacterialflora should be considered when selecting route of administration and class of antimi-crobials and other drugs. General rules used for ruminants can serve as guidelines forprudent drug use until more pharmacokinetic research is done in macropods. Forest-omach ciliates are mostly holotrichs with a few spirotrichs. The morphology of the for-estomach protozoa is distinct from those of domestic species. A new family ofentodiniomorph protozoa (Macropodiniidae) has been proposed to describe these

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unique protozoa.18 Anaerobic fungi in the forestomach are similar to those found inruminants and function to assist with plant fiber breakdown.19

Small Intestine

The small intestine is typical of that of other mammals with the exception that it is rela-tively shorter than that of other herbivores.3 Brunner’s glands, which have an alkalinesecretion, empty either into the pyloric mucosa of the stomach or the intestinal epithe-lium, depending on the species.20 A common bile and pancreatic duct empties into theduodenum. Lactase activity is high in the intestines of pouch young but low in adults.In eutherian mammals, lactase activity is caused by a neutral b-galactosidase which isfound extracellularly on the microvillous membrane. In macropods, however, theactivity is caused by an acid b-galactosidase found intracellularly in lysosomes of en-terocytes. This requires lactose to be taken up into the enterocytes via pinocytosis,a relatively slow process.21 Because macropod milk is relatively low in lactose, thisslower process is usually adequate.

Cecum and Colon

Macropods possess a simple cecum with a mobile body and apex.22 The colon can bedivided into proximal and distal regions, with the proximal colon having a wider luminaldiameter (Fig. 1). Taenia are present on the proximal colon but are not well developed,which results in poorly defined haustrations. A gastrocolic ligament attaches the prox-imal colon to the tubiform forestomach. The colon ends with the rectum, whichempties into a cloaca, a common opening shared with the urogenital system. Thececum and proximal colon serve as a secondary site of microbial fermentation.Protozoa, however, are not present in the hindgut. The distal colon is the region inwhich water absorption primarily occurs, resulting in well-formed fecal pellets.23 Thelength of the cecum and colon is relatively longer in grazers than in browsers,24 whichis thought to be caused by a higher fiber content of grasses. Increased colon lengthalso may be seen in species from arid regions as an adaptation for conserving water.

ENERGYMETABOLISM

On average, marsupials have a lower metabolism rate than their eutherian counter-parts. The basal metabolic rate of most marsupials falls between 65% and 74%(mean, 70%) of the calculated basal metabolic rate for a eutherian mammal of equalweight, with macropods ranging from 57% to 88%.25 This lower basal metabolicrate results in lower average body temperatures and an overall decreased caloricrequirement when compared with eutherians. The maintenance energy requirementfor marsupials is usually 150% to 250% of the basal metabolic rate, with larger marsu-pials having a maintenance energy requirement in the lower end of the range.25

The primary source of energy for macropods is short-chain fatty acids produced bymicrobes through fermentation. Most short-chain fatty acids are produced and ab-sorbed in the forestomach, with production and absorption highest in the sacciformregion.17 The cecum and proximal colon also serve as a secondary site of microbialfermentation. Short-chain fatty acids can lower the forestomach pH from approxi-mately 8.0 in a fasting animal to approximately 5.0 in a recently fed animal. The typesand proportions of short-chain fatty acids are similar to those produced in the rumenof domestic species. Like in ruminants, large proportions of acetic acid are convertedto butyric acid, the principle short-chain fatty acids used by the forestomach epithe-lium for energy. Byproducts of this reaction are ketone bodies, especially acetoace-tate, which can be further oxidized by other tissues. Unlike ruminants, however, in

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which this ketogenic activity occurs throughout the squamous epithelial lining of therumen, ketogenic activity in macropods is restricted to the cardiac glandularmucosa.26

Microbial fermentation also results in production of ammonia, which serves as theprimary nitrogen source for microbial protein synthesis. The ability of microbes tobreak down proteins, other microbes, and nonprotein nitrogen sources into ammoniaallows macropods to use different nitrogen sources of varying quality. During periodsof nitrogen shortage when ingesting a low-protein diet, macropods are able to recycleendogenously produced urea into the gut to be used as a nitrogen source instead ofexcreting it in the urine.27 Gases produced by forestomach fermentation are primarilycarbon dioxide and hydrogen. Methane is also produced, especially during activeeating, but at lower levels compared with ruminants.3

Soluble sugars are rapidly digested and absorbed in the sacciform forestomach.This process results in little disaccharidase activity in the small intestines, becausefew digestible carbohydrates ever reach this location before they are broken downby microbes and absorbed. Similar to sheep, there is minimal glucose uptake intothe liver. Instead, the liver continuously produces and releases glucose into the bloodthrough gluconeogenesis, which occurs postprandially and during fasting. Macropodsexhibit considerable tolerance to hypoglycemia induced by intravenous injections ofinsulin28,29; however, they are much less tolerant of hyperglycemia.29

The tubular flow of ingesta through the macropod forestomach results in a shorterretention time. One disadvantage to this system is that digestibility of the ingesta islower compared with ruminants of similar size. An advantage of this system is that die-tary fiber continues to move through the forestomach regardless of fiber length andsize. In ruminants, the rumen retains fiber particles until they are degraded to a certainsize, which prolongs digestion and results in greater rumen fill and decreased dietaryintake. High-fiber diets can limit food intake in ruminants. On the other hand, dietaryintake in macropods depends less on fiber content. Smaller macropods (with largersacciform forestomachs) are more affected by dietary fiber than the larger grazingmacropods.

BEHAVIOR

Most macropods are either nocturnal or crepuscular and rest during the hottest part ofthe day. In captivity, however, they also may be active during the day, especiallyduring periods of mild weather. The smaller species tend to be more solitary, whereasthe larger, grazing species are more gregarious and form groups called mobs. Theformation of groups while feeding is an adaptation to better protect the macropodsfrom predators. These feeding groups may even be formed from different species.30

In captivity, many macropod species are kept in small groups, including mixedspecies mobs. Keeping a gregarious species in isolation may result in anxiety andstress.

Macropods prehend food with their incisors. The forelimbs also may be used formanipulation of food items. Macropods differ from ruminants in the way they processfood items during mastication. Although ruminants loosely chew their food beforeswallowing, macropods chew their food thoroughly upon ingestion. Ruminants laterregurgitate the coarse ingesta in coordination with rumen contractions for remastica-tion and reswallowing (rumination). Macropods do occasionally regurgitate, remasti-cate, and reswallow food, a processed called merycism. This process is not truerumination because it is not integrated with forestomach contractions. Merycism isnot performed as frequently as rumination is in ruminants because the process is

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not necessary for further breakdown of ingesta. The act of merycism has beendescribed differently for different species, but it can involve a rather violent heavingaction that may be confused with hiccups or choke. The frequency of merycismmay depend on diet, with high-starch diets increasing the frequency.15 Starches areeasily fermentable and rapidly reduce the pH of the forestomach. It is believed thatmerycism is an adaptation that helps to stimulate saliva production, which in turnbuffers the ingesta in the forestomach and raises the pH. A second behavior thatconsists of rhythmic jaw movements several hours after feeding is also thought tobe a method of stimulating saliva production in response to a low forestomachpH.17 This behavior does not involve regurgitation or mastication.

Some macropods have developed adaptations that allow them to survive extremeconditions. Tammar wallabies on the Abrolhos Islands have evolved physiologic adap-tations that allow them to drink seawater during summers when fresh water is scarce.In contrast, Eastern gray kangaroos are adapted to low-sodium environments. Thecommon wallaroo has physiologic adaptations that allow it to survive arid regionswhere forages are low in protein and high in fiber. The red kangaroo’s solution tosurviving the same arid regions is to be more mobile and travel great distances tograze where forage quality is highest. The installation of wells and dams for livestock(primarily sheep) by European settlers in Australia has allowed some macropods tosurvive in areas where populations were previously limited by drought. Similar tocamels and burros, macropods have the ability to conserve their plasma volumewhen subjected to moderate to severe dehydration.31 The forest-dwelling species,such as Parma wallabies and pademelons, have higher protein and energy require-ments and are less able to adapt to extreme conditions.

CAPTIVE DIET

In captivity, macropods should be given a diet that best approximates the forageconsumed by wild members of a given species. Access to high-quality grass pastureis recommended, especially for grazing species. Nontoxic browse items also can beoffered to provide variety and mimic natural behaviors. For many species, providingfresh limbs with leaves and bark allows macropods to consume the leaves and stripthe bark, which also provides behavioral enrichment.

Basic captive diets mimic those fed to ungulates. Items are given in lower quantitieson a per weight basis, however, because of lower metabolism rates of macropods. Ifoverfed, some species (especially smaller ones) are predisposed to obesity. Goodquality grass hay is recommended ad libitum for all species, especially if not kepton a grass pasture. Quality is important because coarse, sharp, or abrasive food items(eg, oat awns, stalky hay, hay contaminated with thorny plants) can cause oral traumaand provide an avenue for secondary bacterial infections that lead to soft tissue infec-tions, dental lesions, and osteomyelitis (commonly but controversially referred to as‘‘lumpy jaw’’). Food items should not be too soft either (eg, bread), because soft foodsdo not adequately toughen the oral mucosa or wear the teeth to allow molar progres-sion. Macropods are susceptible to toxoplasmosis from ingesting food items contam-inated with infected cat feces. Contamination of hay from barn cats at the hay storagelocation has been implicated as the source of toxoplasmosis outbreaks in severalzoologic collections. It is recommended that food items be fed elevated from theground (eg, in a hay rack, elevated bowl, or trough feeder) to prevent contaminationwith feces and reduce the transmission of parasites. Food containers should becleaned daily and regularly disinfected. To reduce food competition and aggression,multiple feeding areas are recommended when macropods are kept in a group.

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Pelleted rations are also recommended in moderation. Several commercially avail-able pellets formulated specifically for macropods are available. Vegetables can beoffered in small amounts, and fruits can be used only as an occasional treat. Theseproduce items must be restricted to a small proportion of the diet, however, becausethey contain higher levels of simple sugars and carbohydrates and are easily ferment-able, possibly leading to gastrointestinal and dental problems. Sweet feed mixesshould not be used for the same reasons. The smaller, forest-dwelling species thatare primarily browsers are more tolerant of larger amounts of produce in their dietthan the grazing species. Items such as bread, peanut butter, jam, and other sweettreats may be helpful in getting a macropod to take medications, but they shouldnot be a regular part of the diet. Salt blocks are recommended for the speciescommonly kept in captivity as a source of electrolytes and minerals. Fresh, clean watershould be offered daily to all macropods. Although some species are drought-tolerant,captive diets usually contain less moisture than wild forages, which increases thecaptive animal’s need for water intake.

Vitamin E is an antioxidant required by macropods to prevent myopathy, or whitemuscle disease. Hind limb weakness that progressed to paralysis, muscle wasting,and death was described in captive Quokkas fed a commercial sheep pellet.32 Smallerenclosure sizes were found to increase the requirement of vitamin E because of theadditional stress of overcrowding. Myopathy was prevented with vitamin E supple-mentation regardless of enclosure size, however.33 In most species of animals, sele-nium can be used as an antioxidant substitute in the place of vitamin E to preventmyopathy, but selenium supplementation alone was found to be ineffective in prevent-ing myopathy in Quokkas and Tammar wallabies.4,34 Vitamin E supplementation isrecommended for all macropods. The amount of supplementation required will varybased on the vitamin E content of the diet ingredients. Feeding large amounts of variednatural browse may reduce the need for vitamin E supplementation.

NUTRITION OF JOEYS

Macropods have a short gestation period, with most growth and development occur-ring postpartum while the joey is in the pouch attached to the mammary gland. Initially,the joey is permanently attached to the teat, but later it develops the ability to detachand reattach at will. Unlike that of eutherians, marsupial milk composition changesdramatically over the course of lactation to accommodate changing nutritional require-ments of the developing joey. Early in lactation, the milk is low in total solids, lipids, andproteins and the carbohydrate fraction is relatively higher and composed of oligosac-charides.35 Later in lactation, the milk composition increases in lipids and proteins, andthe oligosaccharides are replaced by low levels of monosaccharides.35 Macropodspossess four teats, although only one develops for each joey. As a survival strategy,some macropods have the capability of having three joeys at one time, each ina different stage of development. One joey can be out of the pouch but still nursing(joey-at-foot) while another is developing in the pouch (pouch joey) and a third is wait-ing in utero as a result of embryonic diapause. This occurrence can result in teats in fourdifferent stages of lactation: one undergoing regression from a previous joey, one forthe joey-at-foot, one for the pouch joey, and one undeveloped teat for the joey yetto be born. The two teats that are actively lactating simultaneously produce milk ofdifferent compositions that are appropriate for each joey’s stage of development.

The need for hand-rearing can occur as a result of health issues or death of the damor if the dam throws the joey from the pouch as a result of stress. Artificial rearing ofmacropod joeys can be challenging, with joeys in early stages of pouch development

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having a low success rate. As a joey ages, however, the success rate dramaticallyincreases. Because milk composition changes over time, so too must that of the arti-ficial milk replacers. A commercial product (Wombaroo, Perfect Pets Inc., Belleville,MI) has been developed specifically for macropods. The feeding amounts, frequency,and type of formula should be fed according to the product’s species-specific recom-mendations for the age of the joey. Body measurements, and not weight, should beused along with species-specific growth charts to determine the joey’s age. Theweight of the joey can be decreased by dehydration and a history of suboptimal nutri-tion, which might result in an underestimate of age when this variable is used alone.Artificial milk replacers designed for other species and whole milk from other speciesshould not be used, because they often contain higher levels of oligosaccharides (eg,lactose, sucrose). Because of the previously described slower mechanism for diges-tion of these oligosaccharides in macropods, their use can result in severe problems,such as osmotic diarrhea, gastrointestinal bacterial overgrowth, and cataracts. Moredetailed information on hand-rearing macropods is available.36

SUMMARY

Although often compared with ruminants, macropods exhibit many unique differencesin the way they acquire, process, and digest food. These differences and an overalllower metabolic rate affect the way macropods should be fed in captivity. Differingdiets in the wild have resulted in different anatomic variations that also must beconsidered. The unique developmental process of marsupials has significant effectson the nutrition of growing joeys, which must be taken into account during artificialhand-rearing.

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2. Dawson TJ. Diets of macropodoid marsupials: general patterns and environ-mental influences. In: Grigg G, Jarman P, Hume I, editors. Kangaroos, wallabies,and rat-kangaroos. Sydney: Bearry; 1989. p. 129–42.

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