Colyer Institute- Captivity Disorders in Elephants Impacted Molars and Broken Tusks

Gefangenschaftskrankheiten beim Elefanten

Captivity Disorders in Elephants
Impacted Molars and Broken Tusks

D.A. Fagan, J.E.Oosterhuis, and A. Roocroft.

THE COEFFICIENT OF ABRASIVITY IN THE WILD AND IN CAPTIVITY

The eruption of the young elephant's first molar tooth into its mouth occurs before the tooth is sufficiently calcified to function normally (See Fig 8). The design of this animal's oral cavity incorporates by intent an ability to consume a diet of milk from its mother for the first six to twelve months of its life. As the youngster learns to use its trunk to begin feeding itself, soft grass is gradually added to the milk diet for another six months to a year or more. The elephant's eventual mixed cellulose based diet will be quite abrasive. However, if and/when the rate of abrasive wear of the primary "in-use" molars exceeds their rate of mineralization, exposure of the pulp tissue of the molar is sure to follow. Therefore, it is imperative that the abrasivity factor of the young elephant's diet is not permitted to exceed the mineralization rate of its immature, developing, continuously, calcifying dentition; or irreversible pulpal necrosis will develop, as occurred in a group of African juveniles imported into the United States some years ago. Eventually in cases of infection of the dental pulp, a peri-apical osteomyelitis of the alveolar process will result, and in time the tooth will be prematurely exfoliated or must be extracted. In captivity, if the young elephant must be hand reared, care should be taken to provide a non-abrasive diet until the animal's molar teeth are fully mineralized at about two years of age. If these procedures are not observed, Gefangenschaftskrankheiten symptoms could easily develop.

Fig. 8A.

Fig. 8B.

Fig. 8. Two views of early molar growth and development within the body of the mandible of a neonatal Asian elephant. Fig. 8A - is a sagittal section of molar 1 as it begins to erupt into the oral cavity, and clearly demonstrates the incomplete mineralization of the molar within its encapsulating Dental Follicle. Fig. 8B - is an oblique view of the right lateral aspect of a neonatal mandible with a portion of the lateral alveolar bony crest removed to facilitate visual access, and clearly demonstrates the systematical formation of the incompletely mineralized enamel plates of molar 1 at the time of birth.

However, after a few yeas when the animal's systemic calcification process is in full progress, adequate abrasivity in the diet becomes an absolute requirement. This dietary abrasivity is necessary in order to begin the life-long process of eroding away the chewing surface of the tooth at a uniform rate to facilitate and accommodate the anticipated normal rate of dental wear, growth and replacement. Fortunately, cellulose is generally quite abrasive, unless its sole source is a pelletized feed, delivered in the manner of a 'pre-digested TV dinner". Elephants are individuals, and they can be very selective consumers; however, they are also voracious eaters. The actual variety of foodstuffs consumed by each individual should be considered in the determination of that individual's dietary coefficient of abrasivity. Browse, if and when available, should be offered in addition to the grass-based diet. This is well corroborated by Eltringham in his discussion of feeding habits of Loxodonta. In their natural habitats, elephants spend a good deal of time and effort stripping bark off of trees and branches, and then chewing on and "playing" with these branches of various sizes (see Fig. 9). In fact, Ian Redmond has documented elephants digging and chewing rocks in Africa's Elgon Caves, which on occasion results in over abrasion of their dentition. The wear and tear of this coarse cellulose-based natural diet material provides an important additional source of necessary abrasivity for the molar dentition. Elephants in captivity on occasion require more hassle-factor per mouthful of nutrients than is usually provided. This can be added in a variety of ways. The addition of the large root ball of a freshly harvested tree stump, complete with all of the little feeder roots with many small deposits of abrasive soil still attached. Do not "clean" this root ball, as the attached dirt, not only delivers needed "hassle-factor", but provides a great deal of occupational time and therapy during the process of "eating".

Fig. 9. An African elephant seen in the wild chewing branches. It is clear that elephant's seem to utilize larger branches, and on occasion rocks to influence and facilitate the wear and/or exfoliation of their molar dentition. There is evidence that it may be advantageous to enable this type of activity in captive environments.

In 1884, it was observed and reported by Sterndale that "In the wild state, sand and grit, entangled in the roots of plants, help in the work of attrition". Short noted that "the tame animal, getting cleaner food, and not having such wear and tear of the teeth, develops a deformity by the piling over of the plates of which the grinder is composed." In captivity, many zoological diets are presently formulated to be nutritionally adequate; however, with some individuals there is growing evidence to suggest that there may be insufficient abrasivity in these diets. Some have suggested that this abrasivity can be supplied by the addition of an inexpensive coarse dental pumice to the diet. However, sand impaction colic is never out of the picture if too much particulate abrasive is added to any diet. The addition of a more naturally abrasive food source than that presently selected may be somewhat more appropriate, if it is determined that additional abrasive wear is indicated in order to maintain the normal wear of the animals dentition. This practice may avoid the complications of invasive dental extraction therapy. Clearly in this situation, an ounce of prevention is worth a great deal more than a pound of cure. It is important to remember that elephant molar formation is a complex, lifelong process, and when the animal's molars stop working, the elephant stops eating - generally. Estes reported that many old elephant bulls relocate to swampy zones "where they can find soft vegetation they can chew with their worn-out teeth". Although relocation options are more limited in captive environments, perhaps improved monitoring of the impact of dietary abrasivity upon the rate of dental wear with appropriate alteration of the diet will introduce something similar in order to promote longer, healthier lives in the captive population.

Introduction
Development Process of Molars
The Coefficient of Abrasivity in the Wild and in Captivity
"Gefangenschaftskrankheiten" And Molar Mal-Position
Fundamental Tusk Structure
Summary and References

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