- Elephants are the largest extant herbivores on earth.
- The average weight of adult Asian elephants (Elephas maximus) tends to be less than that of adult African elephants (Loxodonta africana), in the wild their weight ranges overlap (Asian, 1,800-5,000 kg [4,000-11,000 lb]; African, 1,800-6,000 kg [4,000-13,000 lb])
ELEPHANTS FEEDING IN THE WILD
Numerous studies on feeding habits of African and Asian elephants indicate that they are generalist feeders, consuming a large number of plant species but with wide variations regionally and seasonally in the proportions of grasses, sedges, forbs (herbaceous flowering plant), shrubs, and trees. Fruits, bulbs, plant bases, and roots also are consumed.
Both browsing and grazing are practiced, but elephants tend to take plant types in proportion to their availability. Browsing is commonly defined as consumption of forbs and the tender shoots, twigs, and leaves of trees and shrubs, whereas grazing is the consumption of grasses and sedges. Free-ranging African elephants select relatively young plant parts if food supplies are not excessively restricted by drought, overpopulation, or habitat degradation.
One of the most obvious and unique physical features of the elephant is its elongated upper lip and nose, forming a muscular trunk capable of reaching from ground level to high branches in its search for food. Although strong enough to lift an entire tree, the trunk is delicately prehensile and can be used to pick a single grass inflorescence. Food is transferred to the mouth where there is a large grinding tooth in wear on each side of the upper and lower jaw.
Unlike the horse, the elephant has no canines or lower incisors, and the upper incisors, when present, have been modified to form tusks. The grinding teeth do not succeed each other vertically, as in most mammals, but migrate forward from the back of the jaw. As the foremost tooth wears down, it is pushed out, often breaking off in transverse plates. Transverse ridges on the teeth produce an occlusal grinding surface that is particularly important for reducing siliceous or highly lignified foods to a more digestible particle size. If a tooth erupts at an improper angle, or wears unevenly, grinding surfaces may not meet, and the physical form of the diet may need to be altered to assist in the particle size reduction normally accomplished by chewing.
Chewed food, mixed with saliva, passes down the esophagus to a simple stomach, connected, in turn, to the small intestine, which then joins with the colon. At this latter juncture there is a cecum of considerable proportions. The colon is sacculated but not compartmentalized, and the majority of the digesta is located in the proximal two-thirds. Digestion of protein begins in the stomach and continues in the small intestine, where fat and carbohydrate are also being broken down to absorbable forms. The cecum and colon are inhabited by anaerobic bacteria and protozoa similar to those found in the rumen and reticulum of the ruminant. Anaerobic bacteria and protozoa have also been found in the small intestine, although concentrations of protozoa are lowest in the duodenum and increase in the more distal jejunum and ileum. These microorganisms digest plant fiber (principally cellulose and hemicellulose) that otherwise could not be used, since elephants, like other herbivores, have no fiber-digesting enzymes of their own. Microbial fermentation of fiber, other incompletely digested compounds, and lactic acid formed in the upper tract results in production of volatile fatty acids that can be absorbed and used for energy.
THE IMPORTANCE OF FIBER
In animals that have evolved as herbivores, the physicochemical characteristics of dietary fiber play an important role in normal gastrointestinal function. The amount and form of digesta reaching the lower gut of the elephant influences the character of the fermentation occurring there, and may affect the rate at which fermentation products are produced and absorbed and the rate at which undigested residue is excreted. When dietary fiber concentrations are low and concentrations of rapidly fermented materials, like starch, are high, fermentation rates will be accelerated, gut motility will change, the bowel can become distended with gas, and abdominal pain may result.
WHAT TO FEED ELEPHANTS
Hays of various types generally constitute the foundation of feeding programs for elephants. Grass hays are commonly used, although they vary greatly in nutrient content, and many elephants may benefit from a combination of grass and legumes. Hays that are dusty, moldy, or infested with blister beetles, poisonous plants, or other dangerous substances should never be used.
The composition of grass hays can vary widely, dependent largely upon soil fertility and stage of maturity when cut. For example, bermudagrass hay that has not been fertilized with nitrogen and is cut when mature, may have only 4% CP, whereas properly fertilized bermudagrass cut at the early heading stage, or before, may have up to 14% CP. Perennial legumes, such as alfalfa (Medicago sativa) and common red clover (Trifolium pratense) have relatively high CP concentrations because of the nitrogen-fixing bacteria that live in their root nodules.
- The nutrient requirements of the elephant have not been defined, however, the similarities in digestive strategies of the elephant and the horse suggest that the nutrient needs of the former might reasonably be compared to the nutrient requirements of the latter.
When nutrient analysis is done for typical hays, deficiencies of several nutrients are apparent. Protein concentrations are low in many grass hays compared to the needs of growing young, pregnant and lactating females, and breeding males. Some of the poorer grass hays are too low in protein for maintenance of adults, but these conclusions should be based on analysis. Calcium concentrations tend to be high in legumes and low in grass hays, whereas Phosphorous and Sodium tend to be low in both grass and legumes. Dependent upon the region where grown, low concentrations of Iodine, Cobalt, Selenium, Zinc, and Copper may be seen. Vitamin A (from beta-carotene) and vitamin E can be inadequate if the hay has few leaves or is badly weathered, and concentrations of both nutrients decline with storage time.
Although daily digestible energy (DE) requirements are commonly met by allowing elephants to consume hay until their appetites are satisfied, fiber concentrations in mature grass hays may be so high and DE concentrations so low that gut fill will physically restrict intakes below the needs of young, growing elephants or of lactating females. Thus, supplements to hay must be formulated to ensure that intakes of specific nutrients and of digestible energy (DE) will be sufficient. Proposed minimum nutrient concentrations (DM basis) in elephant diets, based largely on extrapolation of nutrient requirements of horses, are presented in the following table:
Proposed minimum nutrient concentrations (DM basis) in elephant diets based largely on extrapolation from nutrient requirements of horses.
Breeding, early pregnancy
Growth of juveniles
|Crude protein, %||8-10a||12||12-14b||12-14c|
|Vitamin A, IU/kg||3,000||3,000||3,000||3,000|
|Vitamin D, IU/kg||800||800||800||800|
|Vitamin E, IU/kg||100||100||100||100|
a.Adult maintenance, 8% CP; breeding bull, pregnant cow (1st two-thirds of pregnancy), 10% CP.
b.First yr of lactation, 14% CP; 2nd yr of lactation, 12% CP.
c.Weanling, 14% CP; 3-yr-old, 13% CP; 4-yr-old to 12-yr-old, 12% CP.
Pelleted feeds can be useful in correcting the inadequacies of hay. To avoid digestive upsets, the introduction of either pellet into the diet should be gradual (increasing slowly over 2 wk), and the amount fed should be appropriate to need but should not exceed 50% of total dietary DM (dry matter basis).
photo credit: AZA Elephant TAG and SSP
Thus, it is apparent that appropriately formulated pellets can be used in a variety of ways to correct the deficiencies of forage. However, if those deficiencies are extreme, it may be more cost-effective to buy and use only hays that meet Quality Standard 4 or higher of the Hay Market Task Force of the American Forage and Grassland Council (see NAG Fact Sheet 001, 1997, Hay Quality Evaluation). See my post about new research being done by Disney’s Animal Kingdom on the herbivore diet.
Assuming that pellets are compounded and used as described, other nutrient supplements should not be needed. However, it has been suggested that biotin supplements improve foot health, and that zinc supplements may be needed to ensure normal immune function. Also suggested is that large doses of a water-soluble derivative of vitamin E protect more effectively, than the usual vitamin E compound added to feeds (D,L-alpha-tocopheryl acetate), against myopathies and other expressions of oxidative damage to cells.
Anecdotal reports of improvements in foot health associated with biotin supplementation of horses or elephants are almost invariably confounded by improvements in foot husbandry. Considering the evidence of biotin synthesis in the digestive tract of horses, the similarity of the elephant digestive tract, and the difficulty in demonstrating biotin deficiency in any species fed natural diets without use of an antibiotic or sulfa drug to limit microbial synthesis in the intestine, it is surprising that responses to biotin supplements have been noted. It is doubtful that this issue will be resolved until an adequate double-blind study is conducted, in which the person administering oral biotin or a placebo does not know which is which, and likewise, the person scoring foot health does not know which animals received biotin and which received the placebo. It is implausible that the application of biotin-containing products (ointments) to the foot or toenails will result in improvement.
With respect to vitamin E requirements, serum concentrations of alpha-tocopherol in captive elephants responded markedly (rising from 0.1 to 0.4 mg/ml) to a large oral dose (4.8 IU/kg body weight) of water-soluble vitamin E (D-alpha-tocopheryl polyethylene glycol succinate [TPGS]) compared to little response from equal or higher doses of D-alpha-tocopherol or D-alpha-tocopheryl acetate. When TPGS was provided at 6.6 IU/kg body weight, serum alpha-tocopherol concentrations rose to about 1 mg/ml.25,26 Death of a 17-mo-old Asian elephant was previously reported when plasma concentrations of alpha-tocopherol in this animal and others in the herd were undetectable (<0.1 mg/ml).
Vitamin E Levels in Elephants
Appropriate levels of Vitamin E are essential to muscle function in elephants. Low Vitamin E can lead to muscle weakness and an inability of animals to recover from anesthesia, have appropriate birth contractions and other medical related issues. It is generally considered that elephants should have Vitamin E levels in the blood of around .5 -1.0 micrograms/ml.
|Species||N||Vitamin E (µg/ml)|
|African (North American)||223||0.47 +/- 0.75|
|African (European)||57||0.33+/- 0.46|
|Asian (North American)||945||0.50 +/- 0.36|
|Asian (European)||20||0.24 +/- 0.16|
|African||38||0.50 +/- 0.25|
|Asian||12||0.27 +/- 0.0|
|Asian||26||0.77 +/- 0.05|
Table found in: Fowler, M.E., and Mikota, S.K. (2006). Biology, Medicine, and Surgery of Elephants. Ames, IA: Blackwell Publishing.
A captive Asian elephant fed timothy hay, oat grain, carrots, lettuce, and pellets was reported to exhibit hyperkeratosis and a poor inflammatory response in infected vesicles above the toenails. A presumptive diagnosis of immunodeficiency, secondary to zinc deficiency, was made when an improvement was noted following administration of a zinc carbonate supplement. The concentration of zinc in dietary DM (dry matter) was reported to be 22 mg/kg before supplementation and 54 mg/kg afterward. Unfortunately, it isn’t clear whether these were analyzed or calculated values, and if calculated, whether consideration was given to missing values for zinc in some dietary ingredients. In addition, dietary zinc concentrations given in the text of this report differed from those in the tables.
It is noteworthy that 88 young African elephants (<2-9 yr initially), housed in dirt lots with small areas of mud (man-made in dry weather), fed bermudagrass hay, alyceclover (Alysicarpus vaginalis) hay, and ADF16, and subjected to regular veterinary examination for 6 yr, grew normally and showed no signs of biotin, vitamin E, or zinc deficiency.
FOR FUN: Predicting Elephant Birth Date at Disney’s Animal Kingdom
It has been suggested that use of bran may prevent colic in elephants. Horses and elephants are not “meal-eaters”, but have evolved to consume large amounts of food throughout the day. Bran, when offered along with pellets as part of a meal, provides a bolus of high fiber material to the gut. By contrast, consumption of properly selected hay throughout the day better simulates the natural feeding strategy of elephants and provides fiber continuously over a longer period.
HOW MUCH TO FEED
- Estimates of daily dry matter intake by adults of about 1.0-1.5% of body weight. Using similar methods with wild adult Asian elephants, daily dry matter intakes have been estimated to be 1.5-1.9% of body weight. Daily dry matter intakes of timothy hay by two captive 6-yr-old female African elephants, measured for one 7-day period in summer and a second 7-day period in winter, were 1.4-1.6% of body weight. In another study, daily dry matter intakes of captive Asian and African elephants fed grass hays were 1.3 and 1.7% of body weight, respectively.
WHEN AND HOW TO FEED
- Varied feeding schedules dispersed both spatially and temporally throughout the day and night are required
- Mechanisms to deliver food to elephants during the day and night should be implemented (e.g., changing animal care staff schedules, automated feeders, hanging feeder nets, etc.). Feeders should be located in multiple locations to discourage undue competition or aggression over feed items
WATER AND MOATS
- While outdoors and weather permitting, elephants must have regular access to a water source, such as a pool, waterfall, misters/sprinklers, or wallow that provides enrichment and allows the animals to cool and/or bathe themselves. Standing water in indoor floor areas can cause foot problems and become a breeding ground for bacteria. Floors must therefore be impervious to water, quick to dry, and sloped to a drain. Floor surfaces must be relatively smooth, but not enough so that they become slippery when wet. Conversely, very rough surfaces may cause excessive wear or irritate footpads. When water containers are used, drinking water must be cleaned and refreshed at least twice a day. Containers must also be cleaned daily.
- Elephants should be given ample access to fresh, potable water daily. Water free-choice is not a requirement; however, offering water at least twice a day and more frequently depending on temperature, humidity, and the amount of exercise the elephant receives is recommended.
Adult elephants consume an average of 140 to 200 L of water per day.
- Many zoos continue to offer produce to large herbivorous animals. When used in small amounts, fruits and vegetables are not harmful and may help when shifting or medicating elephants. However, other palatable products, such as leaf-eating primate biscuits can be used in small amounts (a few cubes), as an enticement to shift/move, at appreciably less cost. At one major U.S. zoo that still feeds apples, carrots, and leafy greens, 49% of the cost of the elephant diet was due to produce, whereas those high-cost, high-moisture foods contributed 5% of diet dry matter.
KEEPING TRACK AND RECORD KEEPING
- Nutritional content is a critical tool for assessing overall nutritional wellbeing. Daily intake records may also be valuable to maintain. Overall energy content of the diet must be assessed in relation to the body condition scores for each elephant and diet composition adapted as needed.
HOW TO ENCOURAGE NATURAL FEEDING BEHAVIORS
- Opportunities must be provided for elephants to acquire food using multiple foraging behaviors. Food must be provided in areas where it is less likely to be soiled. Excess or waste food must be removed daily.
- Opportunities for searching, browsing, grazing, reaching, opening, etc. can be provided by scatter-feeding, hiding foods in crevices and substrates around the exhibit, or by using elevated feeders such as hanging hay nets that encourage an elephant to reach for and manipulate its trunk to gain access to the food. Mechanisms that promote physically active feeding behaviors can be incorporated into a comprehensive enrichment plan for the elephants.
- Because exhibit areas are small, and food requirements can generally be met by short bouts of eating, there are long periods of inactivity during which aberrant behavior may develop in a few elephants. This may include consumption of sand or other exhibit substrates, resulting in intestinal impaction. Some zoos have used decomposed granite on ground surfaces which, when consumed, tends to form a stable concretion that is more likely than sand to obstruct the intestinal tract, because it does not break apart readily. It may be most appropriate to thoroughly review and correct husbandry, restrict access to consumable substrates, if feasible, and observe elephants regularly for signs of abnormal behavior. Depression, failure to eat, changes in the odor, appearance (e.g., presence of substrate), and volume of feces, changes in the pattern of defecation (commonly about every 2 hr, but individuals have a characteristic pattern), stretching in a “saw-horse” stance, elevation of the head, and rolling, are colic danger signs. Forced exercise may be helpful in restoring normal gut motility and relieving pain.
- BROWSE: Providing browse for elephants increases foraging time, can add important nutritional benefits, and can promote dental health. As with other food items offered to elephants, it is important to have browse nutritionally analyzed.
Summary of Recommendations
1. Analyze hays for dry matter, crude protein, neutral detergent fiber, acid detergent fiber, lignin, calcium, and phosphorus in a laboratory with demonstrated expertise.
2. Use grass hay or a mixture of grass and legume hays, of known composition, as the base for the diet.
3. Using analyzed and published nutrient concentrations, determine the need for supplemental sources of energy, protein, minerals, and vitamins.
4. When hay mixtures are not adequate to meet digestible energy, protein, mineral, and vitamin needs, consider adding a formulated pellet.
5. When hay mixtures are principally deficient in minerals and vitamins, consider adding a formulated pellet similar to the Herbivore Supplement.
6. Note that grass hay to be fed ad libitum should have 30% or more ADF (acid detergent fiber) to avoid problems with colic.
7. Make all dietary changes gradually (over 1-2 wk) to avoid digestive upsets.
8. Observe elephants regularly and conscientiously.
References (click to view source document):