Successful nutrition of hand-reared zoo mammals requires several steps:
selecting a formula that will support adequate growth and not cause GI upset
offering food at proper intervals, in proper amounts, and in the proper way to ensure acceptance and prevent overfeeding, underfeeding, and pulmonary aspiration
keeping all feeding utensils clean and disinfected
If success is judged in terms of survival and not in comparison with maternal-raised growth and health, most precocial species maintained in captive collections have been hand-reared successfully. Hand-rearing more altricial species (eg, marsupials, rodents, rabbits) is generally less successful unless the young have been dam-raised to a more advanced stage.
Whenever possible, data on milk composition and hand-rearing case histories should be consulted before attempting to bottle-raise a species for the first time. Extensive books with general information on hand-rearing birds and hand-rearing wild and domestic mammals are available. However, milk composition data are not available for most species, and some of the published data are of dubious value. Lactose content of milk varies widely between different species.
Animals that normally consume milk low in lactose (eg, pinnipeds, rabbits) generally produce little lactase and often develop severe GI problems and diarrhea when fed a high-lactose milk (eg, bovine). Similarly, adding sucrose to milk formulas is often contraindicated because many neonates produce little sucrase. Many species have been raised using diluted evaporated milk or commercial calf, lamb, foal, or doe milk replacers (eg, most ungulates), commercial dog milk replacer (eg, canids, procyonids, bears, bats, edentates, mustelids, rabbits, rodents), commercial cat milk replacer (eg, felids), human infant formulas in general (eg, most primates), and soy-based human infant formulas in particular (eg, rabbits, some marsupials). In some cases, these basic formulas can be modified to better suit the needs of a particular species by adding ingredients such as egg yolk, butterfat, cream, and casein. Supplementation with vitamin and mineral products may be warranted. Some companies offer a range of products with different amounts of protein and fat, so the desired amount of protein or fat can be provided in the formula.
For rearing macropods, a specific strategy is necessary. Rearing joeys successfully depends on the right milk composition based on maternal size, length of pouch time, and stage of lactation. Young macropods should be kept in a hygienic pouch at 32–34°C. Milk composition should have an increasing level of fat and protein during the hand-feeding period and a decreasing level of carbohydrate in late lactation. Macropods have a low tolerance for lactose but not for glucose or galactose. Triglycerides account for more than 90% of the milk lipids. Commercial milk replacers for macropods fulfill the mentioned criteria. Joeys should be fed 10–20% of their body weight daily over 6–9 milk feeds through a special nipple adjusted for joeys. (See the table Nutrient Requirements for Hand-Rearing Selected Zoo Mammals.)
Hand-rearing young animals requires practical knowledge, which can be obtained by consulting experts and by reading specialized hand-rearing books on wild or domestic mammals and birds.
Nutrient Requirements for Hand-Rearing Selected Zoo Mammals
-----------------------% of Dry Matter----------------------- | ||||
|---|---|---|---|---|
Animal | Dry Matter, %a | Protein | Fat | Carbohydrates/Lactose |
Horses, rhinos | 8–12 | 15–20 | 2–15 | 59–75 |
Primates | 2–14 | 7–15 | 25–35 | 50–60 |
Elephants, ruminants, pigs | 12–23 | 21–27 | 30–45 | 20–37 |
Rodents, carnivores, deer | 18–34 | 28–42 | 32–55 | 5–25 |
Rabbits, bears | 30–40 | 25–45 | 40–50 | 5–10 |
Seals | 41–61 | 10–20 | 74–82 | 0–2 |
Marsupials | 23–28 | NA | NA | 1 |
Abbreviations: NA, not available. | ||||
a Percentage of the food/milk offered that should be dry matter | ||||
Some species (eg, ungulates, marsupials, mink) should receive colostrum within 12–48 hours after birth to acquire immunoglobulins necessary for survival. Ideally, the colostrum should be from a similar species to that being hand-reared. However, that is usually not available, and therefore colostrum from domestic animals is used. Including some colostrum in the diet of ungulates for up to 2–3 weeks after birth may provide additional local gut protection. Colostrum from domestic cows has proved satisfactory for many exotic ruminants and can be stored frozen. When colostrum is fed, the best way to offer it is from the dam or from a similar species from the same stable. Studies suggest that conspecific serum, collected aseptically, can be given PO or SC as a substitute for colostrum.
Frequency of feeding and the amount fed depend on natural nursing behavior, formula composition, and desired rate of gain, as well as on practical labor restrictions. The stomach capacity of most species can be estimated at 50 mL/kg. Overfilling the stomach leads to GI upset, decreased transit time, and diarrhea. Daily intake, as a rule, should not exceed 20% of body weight/day and should be divided into frequent feedings that do not exceed 35–40 mL/kg. In general, most newborns should be fed every 2–4 hours, and daily metabolizable energy intake (kcal) should be approximately 210 × body weight (kg)0.75(1). Appetite, condition of feces, and general health should be monitored closely. Pulmonary aspiration is the main problem during bottle feeding. Body weight should be recorded at frequent intervals. Smaller, more altricial species often must be fed by stomach tube.
Pearls & Pitfalls
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Also see Care of Orphaned Native Birds and Mammals and Management of the Neonate in Dogs and Cats.
References
Gage LJ. Hand-Rearing Wild and Domestic Mammals. Wiley Blackwell; 2002.
