Infant Development

Nesting Behaviour
Maternal Neglect and Obsessive Behavior
Weaning and Introduction of calves
Handrearing Protocol
    Nutrient Composition
    Okapi handrearing formula
    Formula supplementation
    Feeding apparatus
    Feeding regimen
    Special Considerations
    Other foods
    Weaning process
    Other Zoo's Experience
      Table 1: Nutrient content of the Okapi handrearing formulas
      Table 2. Average Intake of formula (as fed) as a percent of body weight for handrearing calves (n=5)
      Table 3. Conversions for 10% body weight to total formula quantities (by weight, as fed);5 feedings/day
  Both female and neonate rest. (Brookfield)
Remote monitoring system reduces disturbance to the animals. (Brookfield)
Yokohama calf resting
Diagram of creep used in doorway at San Diego to give calf a stall of its own
Overhang attached in stall corner to encourage calf to nest under it. (Brookfield)

Typical first stool

Brookfield calf in layout position
Weighing calf helps monitor health at Brookfield
Calf investigating what dam is eating at Brookfield
Handrearing calf at Brookfield.
St. Louis calf with fractured leg due to maternal trauma

Calves are born after a gestation of 430–435 days (range of 415–455 days in 34 cases). Labor is 3–4 hours in length. If a female is ncomfortable in her surroundings, she may delay the progress of her parturition for a period of time. It is preferable to watch this event from a distance or remotely via a video monitor. A single calf is normal. A healthy calf usually stands within thirty minutes of birth, and generally nurses within two hours of parturition. Extensive maternal grooming and a high frequency of contact between the dam and calf are characteristic of the period immediately following parturition. Nursing bouts are frequent, averaging two bouts per hour during this initial phase. This initial phase of mother-infant bonding lasts from 2 to 7 days.
Maternal trauma immediately after parturition occurs most commonly in primiparous females; however, certain females have shown a tendency to traumatize their calves on successive births. Plans should be in place to observe primiparous and problem females and intervene if aggression to the calf begins or is suspected. Calves from “repeat offender” females may have to be pulled for hand rearing immediately after birth to prevent trauma. Calves up to 4 months of age have been attacked by their dams, resulting in serious injury or death. These attacks tend to be precipitated by novel or unfamiliar disturbances and noises or exaggerated maternal response to a calf ’s behavior. It is recommended that calves be monitored closely to document dam/calf interactions and ensure that good maternal care is exhibited by the dam and to document nursing bouts and early development of the calf.


Nesting behavior: The okapi is a “hider” species of ungulate. A female may leave her calf in its “nest” and not see it again for twelve hours or more (documented in Epulu). In the zoo setting, experience has shown that the female is likely to be located as distant as is possible from her calf while it is in this nesting stage. One change in behavior during this nesting stage is the frequency of nursing which decreases greatly to 2–3 times per day. This nesting behavior is an aspect of their natural behavior that must be given some thought when preparing space for a birth. It is vital for the female to be able to move out of visual contact with the calf. This can be achieved by offering multiple stalls within a barn. If this is not possible, a hide wall can be added within an enclosure. A barrier of pproximately four feet high is sufficient to visually block the calf while it is on its nest.

Several holding facilities have used:

  • hay/straw bales secured atop one another to form such a barrier
  • A creep partition gate has also been successfully used to allow the calf into a stall or small yard, without giving access to the dam
  • The dam can be separated daily from the calf during the nesting phase, allowing the dam to have access to an outside area for several hours each day
  • It has also been possible to manipulate the choice of nest location by attaching a small object on the otherwise flat wall for the calf to sit under

Any changes that need to be made in the area should be accomplished well in advance of the calf ’s arrival, allowing time for the female to become familiar with these changes.
During the nesting phase, calves commonly double their birth weight in 3–4 weeks and triple it by 8 weeks. Okapi calves generally delay their first defecation (meconium passage) until they are 4 to 10 weeks old.

The well-baby exam should take place 24–72 hours after parturition depending on the temperament and experience of the dam, assuming the calf appears healthy. Only staff familiar to the dam should handle the calf; strange scents should be masked prior to re-introducing the pair, as with used bedding. The dam should be able to see the calf from a distance prior to their re-introduction. Okapi calves do not thermoregulate well until they are about 51- 60 days of age so barn temperatures should be monitored closely.


Maternal Neglect and Obsessive Behavior: If the dam is not allowing the calf to nurse, and the calf is otherwise in good health, the calf could go ~24 hours without needing some nutritional support. It is conceivable that the calf could go longer than this with fluid and dextrose supplementation. It is important to determine why the dam is reluctant to nurse the calf. Haloperidol has been used successfully in a very small number of cases to calm the dam enough to allow nursing to occur.

Maternal over-grooming of calves has led to tail sloughing and rectal and vaginal trauma, and is a result of compulsive behavior by certain females and/or management schemes that keep dams and calves in constant close contact during the nesting phase. Much of this abnormal behavior can be eliminated by providing as much space as possible so the dam and calf can be out of site of one another, by using a creep system so the calf can separate itself from the dam, or by locking the dam away from the calf while it is nesting during the day, as the female would normally be browsing away from the calf at this time.


Weaning and Introduction of calves:
A survey was sent to every institution participating in the SSP in 2001. The focus of the survey was okapi calf management in regards to weaning and introductions to conspecifics. It has been deemed important by the SSP that calves are socialized. Socialization can occur prior to, or after, weaning from the dam.
Weaning of calves can be allowed to occur naturally or weaning can be forced by separating the dam and the calf. The choice is being made by individual institutions and is equally divided on how weaning is accomplished. When institutions force weaning, calves have been separated from dams as early as 5 months and as late as 10 months of age with the average age of separation being 8–9 months. The decision to separate calves from their dam is usually based on the declining body condition of the female as older calves continue to nurse and/or overgrooming of the calf by the dam. Each female and calf needs to be monitored individually to determine the necessity of separating.
Calves should be monitored for food intake prior to and during the weaning process. Institutions have not used grain and hay consumption as an indicator of calf readiness to wean. This is a possible indicator that needs to be considered if weanings are going to occur prior to 8-9 months of age. During the weaning process, separation from the dam has not resulted in calves refusing feed. There is likely to be a decrease in consumption, but that decrease should not be more than 60% and should not last for more than three days. Calves are usually separated from the dam during a portion of the day to start the weaning process. This partial separation lasts from one week to a month.

Calves may be separated during the day or at night. Calves may have visual contact with dams during the separation, but this should be limited contact. Contact on a chain link fence line can lead to pacing, increased ocalizations, and other stress-induced behaviors. Some institutions have had to move alves to other areas away from the dam to decrease the level of stress behaviors exhibited. Although calves may appear stressed due to separation, few institutions have thought that the level of stress was excessive (no more than stress caused by natural weanings). After a period of approximately one month, calves are no longer put back in with their dams

Introduction of the calf to other conspecifics occurs at different ages, depending on the institution and the availability of companion animals. Most institutions will introduce mother-calf pairs to other okapi.

Certain criteria are suggested prior to introductions occurring:

  • Calves should be old enough to be off their nest
  • Introductions to either adult males or adult females should
    occur only if the dam has been housed with the other adult prior to calving

Adults normally are very tolerant of young, but can be aggressive toward other adults so it is recommended that adults
be introduced prior to pregnancy and calving. There have been two incidents of aggression from an adult female directed
towards a calf. Regardless of how smoothly most introductions proceed, all introductions need to be closely monitored by
animal staff. When introductions do not occur until after the calf has been weaned, a calf can usually be introduced to any
okapi including a mother-calf pair, adult female, adult male or similar aged conspecific. All of these scenarios have been
successful at one or more institutions. Adult males can work as a companion animal for weaned calves age 6 months up
to 2 years of age
. A possible problem when introducing weaned calves is attempted nursing. These nursing attempts usually
do not occur until after the initial day of introduction. If the calf is persistent in its nursing attempts, the other animal may
become aggressive which could result in the need for separation. Institutions need to be aware that there have been some
problems with males as the companion animal
. To avoid some of the problems already encountered, males should not be
housed too closely to cycling females as this can result in aggressive and/or breeding behavior directed towards the calf.


Okapi SSP Handrearing Protocol updated March 2002

The SSP recommendations are based on the following information and experience obtained with 5 hand-reared
okapis and limited okapi milk data. The SSP okapi handrearing formula has been used successfully at Brookfield Zoo
for 5 handreared calves. However, several other Zoos have raised calves with other formulas. That information is outlined
in section IX. Other Zoo Experiences. In those situations calf health and circumstances varied quite a bit,
which created the need to change the formulas.

I. Nutrient Composition
It has been documented in a number of species that milk composition and output change over time and with sampling
method (Oftedal, 1984). Thus, published values are greatly dependent on the time taken during lactation as
well as the methodology used. This may be the reason for variation in published values. Since relatively few samples
of okapi milk have been published; it is necessary to consider general trends at this point. Below are published values
for okapi milk and final formula used.

  Okapi milk composition







II. Okapi handrearing formula (ALL MEASUREMENTS ARE BY WEIGHT AS FED)
DAYS 0 –2
If the calf is pulled before it is able to receive its mother’s colostrum, it can receive cow colostrum, if available, or a
commercially available product, such as Colostrix (See manufacturers information below).
50% cow colostrum (or a commercially available product) and 50% water
To make 4000 g (141 oz. by weight)
2000 g (70.5 oz.) cow colostrum
2000 g (70.5 oz.) water
Feed at 10 to 12% calf body weight.
48.25% canned evaporated milk
48.25% water
3.5% powdered Esbilac
To make 4000 g (141 oz. by weight):
1925 g (68 oz.) water
1925 g (68 oz.) evaporated milk
140 g (4.9 oz.) powdered Esbilac
Poly-vi-Sol (or pediatric vitamins) 40 drops
Fer-in-sol 40 drops
Lactaid (use bottle directions)
Feed at 10 to 12% calf body weight.
46.25% canned evaporated milk
46.25% water
7.5% powdered Esbilac
To make 4000 g (141 oz. by weight):
1850 g (65.2 oz.) water
1850 g (65.2 oz.) evaporated milk
300 g (10.6 oz.) powdered Esbilac
Poly-vi-Sol (or pediatric vitamins) 40 drops
Fer-in-sol 40 drops
Lactaid (use bottle directions)
Feed at 6 to 10% calf body weight.
This formula should be used for the remainder of the handrearing period.


III. Formula supplementation
There is no need to use distilled water. Boiled water (stored refrigerated) is fine. To avoid diarrhea, lactaid (liquid)
should be added as per the directions on the bottle. Also supplement with an infant multi-vitamin (Poly-vi-Sol - See
manufacturers information below) and an iron supplement (Fer-in-sol - See manufacturers information below).
Supplement at one drop (of each) per 100 g of formula.


IV. Feeding Apparatus
Lamb’s nipple and bottle


V. Feeding regimen
Timing: Since it has been observed that mother-reared okapis suckle primarily in daylight hours, the feedings should
be divided evenly among 5 or 6 feedings in primarily daylight hours. For five feedings, an appropriate schedule
would be: 0600, 0930, 1300, 1530, and 1930.
Quantity: The calf should be fed between 10-12% of its body weight in formula (as fed basis) when it is consuming
either colostrum or the more dilute formula. This is through day 8. Body weight gain should progress similarly to
other calves (Figures 1 & 2.) After that the calf should be offered between 6–10% of its body weight in formula (as
fed basis). It has been found that okapi calves (n=5) can maintain an adequate growth rate while consuming the final
formula at 6% of body weight per day. Average daily formula intake as a percent of body weight for handrearing
calves (n=5) is attached in Table 2. Typical conversions for 10% body mass are shown in Table 3. Example formula
to convert kilograms of body mass to grams of formula: (10% of Body mass in kilograms/# feedings/day) X1000
grams/kg=quantity offered per feeding.
Regardless of the amount or number of feedings offered per day, each feeding should not exceed 3% of calf body
weight. This avoids the probability of GI tract stress if fed too much, too fast.
Actual quantities to be fed should be monitored by weight gain and (sometimes) stool condition. Usually a healthy
okapi calf does not defecate for 30–60 days post partum. Too much formula or too concentrated a formula may
cause GI distress. It is important that diarrhea be avoided. As the dam does not stimulate the calf to urinate or defecate,
no stimulation is needed and it is normal for the first defecation to be several weeks after birth.
The formula and feeding schedule above will provide adequate energy and nutrients to the calf. Too little energy will
not provide for weight gain. Don’t force the calf to eat too much and judge the final quantity offered by increase in
weight gain. A 9-month growth chart of Brookfield Zoo’s 9 okapi calves (4 mother-reared and 5 hand-reared) is
attached in Figure 1. Figure 2 provides a growth chart for the first 30 days for 16 okapi calves.


VI. Special Considerations
The calf should have shelter and be held in moderate temperature conditions.
DO NOT stimulate calf to urinate and defecate. Provide a “nest” area bedded with hay. Most calves lick the floor
while they nest. Make sure the floor substrate is safe for consumption.
The handreared okapi calf should be “wet groomed” over its body with a wet, warm cloth after each feed to simulate
being groomed by its mother. The calf should be encouraged to exercise outside once or twice per day for about 20
minutes per session, weather permitting.


VII. Other foods
Fresh water should be available at all times beginning at birth. Foods that are included in the regular adult okapi diet
should be available to the calf early on to acclimate the calf to these items and eventually prepare for weaning. A salt
block should be made available but, if usage is high, access should be limited to 2–3 days per week.

VIII. Weaning process
The weaning process might need to be individualized for each calf. Weaning depends on solid food consumption, weight gain,
and general health of the calf. Weaning is best performed by keeping the formula at a constant amount (not increasing formula
with body weight increases) while the calf continues to grow and consume more of its adult diet. This will encourage the calf
to eat more of the adult diet. At approximately 20 weeks of age a mother-reared calf will begin to be weaned. Thus at about 19
weeks, it is appropriate to discontinue the formula increases and keep the quantity of formula at a constant level to encourage the
calf to begin consuming more solid food. The calf should not lose weight but may plateau for up to six days during this weaning
process. Once the calf is consuming additional solids and is gaining weight, the quantity of formula can be gradually decreased.
The calf may be completely weaned by 6 to 8 months of age. Care should be taken to ensure that the calf is consuming its
nutritionally complete pelleted diet so that it obtains the nutrients it needs.


IX. Other Zoo’s Experience
Cincinnati Zoo, Marwell Zoo (England), and Oklahoma Zoo have all handreared okapi calves. Calf health and circumstances
varied quite a bit, which created a need to change the formulas. Table 1 provides a comparison of the nutrient
analysis of the formulas

Cincinnati Zoo:
List of Ingredients Used:
1. Cow’s colostrum (high quality according to dairy standards), from a dairy herd in New York
2. Carnation Evaporated Milk, Carnation Company, Los Angeles, CA 90036
3. Esbilac, Pet-Ag, Inc. (Division of Milk Specialties), Elgin, IL 60120
4. Water, boiled and cool/refrigerated
5. Fer-n-sol, Meade Johnson Nutritional Division, Bristol-Myers Co, Evansville, IN 47721
6. Poly-vits Pediatric vitamins, Major Pharmaceutical Corp., Chicago, IL 60612
7. Lactaid, Lactaid Inc., Pleasantville, NJ. 08232
8. Pedialyte, Ross product division of Abbott Laboratory, Columbus, OH 43215
9. Milk Matrix 42/25. Pet-Ag, Inc. (Zoologic), Elgin, IL 60120
10. Nonfat dry milk
Formula Preparation:
Summary: Poucet (1.0, 1999), On day 0 (day the calf was born and removed from the dam), the cow’s colostrum was
given. On day 1 the SSP Protocol was followed. On day 6 and 7 the calf was given Pedialyte. On day 8 he was offered a
mixture of a dilute formula (25% cow colostrum to 75% pedialyte) with Equine Beneac (beneficial gastrointestinal bacteria)
to help re-establish gut flora. At that point the formula was changed to Milk Matrix 42/25 (made by Zoologic, a
product line of Pet-Ag, Inc).
Details: The calf was separated from its dam two hours after birth (day 0) due to his inability to stand. The calf was very
small (10.8 kg or 24 lbs.) and weak. After being warmed the calf was stomach-tubed with cow’s colostrum to help ensure
passive transfer of immunoglobulins. This procedure was done three times during the first 12 hours of life. He nursed
from the bottle two times on day 0. The next day, blood drawn indicated no transfer of immunoglobulins. He was fed
the SSP protocol pre-final formula mixture (see Table 1) on days 2–5. On day 6 the calf presented with bloat and refused
his bottle. He was stomach-tubed with Pedialyte. On day 6 he was immobilized for IV administration of okapi plasma
from San Diego Wild Animal Park (200 cc plasma IV and 60 cc SQ). After the procedure he was fed only Pedialyte for
12 hours. On day 7 he was fed by bottle a dilute formula (25% cow colostrum to 75% Pedialyte). Equine Benebec (beneficial
gastrointestinal bacteria) helped re-establish gut flora. At that point the formula was changed to Milk Matrix
42/25, Nonfat dry milk and Pedialyte (see Table 1). The formula was kept dilute thinking it would be easier for him to
digest. His weight gain was monitored closely and appeared adequate. The quantity of formula fed was ~10–12% body
mass. He defecated during the first week and throughout handrearing had some problems with loose stool. Around his
defecation periods he would refuse his milk bottle but usually take Pedialyte without hesitation. He also would act as
though he was uncomfortable during these periods. He was successfully weaned at 32 weeks.

Marwell Zoo
Details: Elila (0.1, 1997) was handreared from day of birth. She was separated from its dam due to aggression. She was
given colostrum via a stomach tube due to initial lack of interest in the bottle. The calf was offered formula 5x/d formula
unknown. The calf took the bottle well once established. She had a little trouble with wanting the bottle from only
one keeper. Weight gains were similar to mother-reared calves.

Oklahoma City Zoo
Ingredients Used:
1. Evaporated Milk
2. Esbilac, Pet-Ag, Inc. (Division of Milk Specialties), Elgin, IL 60120
3. Water, “sterile” and tap
4. Vitamins
5. Lactaid, Lactaid Inc., Pleasantville, NJ. 08232
Formula Preparation:
Summary: Iosi (0.1, 1998) The first the formula offered was 50% Evaporated milk and 50% “sterile” water. Esbilac was
added so the second formula was 45% Evaporated milk: 45% “sterile” water: 10% Esbilac. Once the Esbilac was added
to the formula Lactaid was added as well. Vitamins were added to the formula at four weeks of age.
Details: The calf was separated from its dam two weeks after birth (day 0) due to pneumonia. The calf appeared weak,
and blood and tissue were seen in the rectum area. At intermittent times throughout handrearing Iosi was offered Resorb
(an electrolyte solution made for calves manufactured by Pfizer) for scours (diarrhea). The calf was offered a formula of
50% Evaporated milk: 50% Water from day of age 11 to 13. The calf was offered a formula of 45% Evaporated milk:
45% Water: 10% Esbilac from day 14 to week 5. From week 5 on the SSP protocol final formula (see Table 1) was
offered. She was offered formula at 8–11% of body mass.

Table 1. Nutrient content of the Okapi handrearing formulas


Table 2. Average Intake of formula (as fed) as a percent of body weight for handrearing calves (n=5). Table 3. Conversions for 10% body weight to total formula quantities (by weight, as fed);5 feedings/day

click to enlarge/shrink

click to enlarge/shrink


X. Products and Sources for SSP Protocol

Protein Technology, Inc.
Santa Rosa, CA 95403
Carnation Evaporated Milk
Carnation Company
Los Angeles, CA 90036
Pet-Ag, Inc. (Div. of Milk Specialties)
30W432 Route 20
Elgin, IL 60120-9527
Mead Johnson Nutritionals
Bristol-Myers Company
Evansville, IN 47721
Mead Johnson Nutritionals
Bristol-Myers Company
Evansville, IN 47721
Contains lactase, an enzyme that breaks down lactose.
(Distributor) McNeil Consumer Healthcare
Division of McNeil-PPC Inc.
Fort Washington, PA 19034

Top  Return to formula

XI. References
Crandall, L.E., 1964. In: Management of Wild Animals in Captivity. University of Chicago
Press, Chicago, IL. p. 624.
Faust, R., 1968. Zusammensetzung einer Okapi-Milchprobe (Okapi johnstoni). D. Zool.
Garten N.F. 35:280.
Gregory, M.E., Kon, S.K., Rowland, S.J., and S.Y. Thompson, 1965. Analysis of the milk of
the okapi. Int. Zoo Yearbook 5:154.
Oftedal, O. 1984. Milk composition, milk yield, and energy output at peak lactation: a comparative review. Symposia of
the Zoological Society of London. Academic Press, NY. Pp: 38-85.
Oftedal, O., Nutritionist. National Zoo, Washington, D.C. Personal communication. 1989.
Senft, B., 1978. Immunologic aspects on artificial raising of newborn okapi. Acta Zoologica
et Pathologica 71:53-58.


Edited by Terry DeRosa, San Antonio Zoo, Fran Lyon, White Oak Conservation Center and Ann Petric, Okapi SSP Coordinator, Brookfield Zoo Illustration: J. Busch
Updated and adapted for the web, Patrick Immens