Successful nutrition of handreared mammals requires 1) selecting a formula that will support adequate growth and not cause GI upset; 2) offering it at proper intervals, in proper amounts, and in the proper way to ensure acceptance and prevent overfeeding, underfeeding, or aspiration into the lungs; and 3) 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 handreared successfully. Handrearing 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 handrearing case histories should be consulted before attempting to bottle-raise a species for the first time. Extensive books with general information on handrearing birds and handrearing wild and domestic mammals are available. However, most 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 (eg, pinnipeds, rabbits) that normally consume milk low in lactose 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. See table: Nutrient Requirements for Handrearing Selected Zoo Mammals
Nutrient Requirements for Handrearing Selected Zoo Mammals
It is preferred that some species (eg, ungulates, marsupials, mink) receive colostrum within 12–48 hours of birth to acquire immunoglobulins necessary for survival. 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 do so is to offer it 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 depends on natural nursing behavior, formula composition, and the desired rate of gain as well as 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% body wt/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 ~210 × body wt (kg)0.75. Appetite, condition of feces, and general health should be monitored closely. Pulmonary aspiration is the main problem during bottle feeding. Body weights should be recorded at frequent intervals. Smaller, more altricial species often must be fed by stomach tube.