The macroscopic intestinal anatomy of a lowland tapir (Tapirus terrestris)

Nutrient Digestibility in Zoo-Kept Tapirs (Tapirus spp) as Compared to Other Herbivores

Tapirs are hindgut fermenters with a natural diet dominated by browse, with a certain proportion of wild fruit. By contrast, diets fed to tapirs in zoos are often dominated by domestic fruit and other sources of easily digestible carbohydrates, which have been linked to obesity and various health problems. We aimed at better understanding the digestive physiology of tapirs, measuring the digestive efficiency of 13 lowland (Tapirus terrestris) and five Malayan (Tapirus indicus) tapirs from five zoos on various zoo diets by recording intake and total faecal excretion. Additionally, we aimed at evaluating zoo diets, by assessing relationships between dietary characteristics and data on intake and faeces consistency, and compared the data gained in the zoo study to those of faecal samples of free-ranging tapirs. Tapirs showed digestive principles reported in other herbivores, such as higher levels of metabolic faecal nitrogen and a lower intake on diets of higher digestibility, or a decrease in digestibility with increasing dietary fibre concentrations. Compared to horses or grazing rhinoceroses, organic matter digestibility in tapirs was more negatively affected by dietary fibre; additionally, tapirs had comparatively low fibre digestibility. This is possibly linked to their comparatively poor chewing efficacy. The readiness to ingest a hay-only diet was directly proportional to the amount of hay in the usual zoo diet, supporting reports that it may be difficult to achieve high hay intakes in tapirs instantaneously. Faeces consistency was closer to the natural condition with higher proportions of roughage in the diet. Compared to a set of faecal samples from the wild, zoo faeces were generally lower in fibre. This study supports previous suggestions that zoo tapirs could benefit, in terms of mimicking their digestive physiology and feeding behaviour in natural habitats, from diets based on a readily ingested roughage source, especially from browse.

Equid nutritional physiology and behavior: an evolutionary perspective

Like other members of the even-toed ungulates (the perissodactyls), equids once had a higher species diversity in the fossil record than they have today. This is generally explained in comparison to the enormous diversity of bovid ruminants. Theories on putative competitive disadvantages of equids include the use of a single toe as opposed to two toes per leg, the lack of a specific brain cooling (and hence water-saving) mechanism, longer gestation periods that delay reproductive output, and in particular digestive physiology. To date, there is no empirical support for the theory that equids fare better on low-quality forage than ruminants. In contrast to the traditional juxtaposition of hindgut and foregut fermenters, we suggest that it is more insightful to sketch the evolution of equid and ruminant digestive physiology as a case of convergence: both evolved a particularly high chewing efficacy in their respective groups, which facilitates comparatively high feed and hence energy intakes. But because the ruminant system, less based on tooth anatomy but more on a forestomach sorting mechanism, is more effective, equids depend more on high feed intakes than ruminants and may well be more susceptible to feed shortages. Arguably, the most under-emphasized characteristic of equids may be that in contrast to many other herbivores including ruminants and coprophageous hindgut fermenters, equids do not use the microbial biomass growing in their gastrointestinal tract. Equids display behavioral and morphophysiological adaptations to high feed intakes, and their cranial anatomy that facilitates the cropping of forage while performing grinding chewing at the same time might be unique. Rather than looking for explanations how equids are better adapted to their present niches than other organisms, considering them remnants of a different morphophysiological solution may be more appropriate.

Microstructure of the Surface of the Tongue and Histochemical Study of the Lingual Glands of the Lowland Tapir (Tapirus terrestris Linnaeus, 1758) (Perissodactyla: Tapiridae)

Simple Summary

This is a detailed study of the surface morphology of the tongue and the lingual glands of the lowland tapir (Tapirus terrestris), which expands the understanding of the adaptation of this species to habitats. The histological and ultrastructural analysis of the lingual papillae and lingual glands revealed the presence of two types of mechanical papillae, namely the filiform and conical papillae, while papillae with taste buds (including the fungiform papillae, vallate papillae, and foliate papillae) formed the second, less numerous group. The filiform papillae differed from those of Equidae or Rhinocerotidae. The presence of nine vallate papillae, localized in groups of two surrounded by a ring, or individually, was unique for the examined female tapir. In addition, the vallate papillae contained irregular pseudopapillae on their surface. The foliate papillae contained several sulci between each folia. The presence of sparse taste buds in the side wall of the vallate papillae and foliate papillae is unique for the tapir. Compared to other Perissodactyla, the number of taste buds in the tapir is limited, although the features of its tongue surface make it possible to distinguish this species from representatives of Equidae or Rhinocerotidae.

Abstract

Although the anatomy of the gastrointestinal tract has been characterized in the lowland tapir (Tapirus terrestris), the exact anatomy of its tongue has not been studied. Samples of the lingual papillae and lingual glands were collected from the tongue of an adult female lowland tapir. The microscopic analysis of the structure of the lingual papillae and the histochemical analysis of the secretion of the lingual glands were analyzed. The tongue of the tapir is divided into the apex, body with a distinct lingual prominence, and the root. Its ventral surface is smooth. The most numerous of the mechanical papillae were the filiform papillae, while numerous conical papillae with a sharp apex or more rounded papillae were present in the root of the tongue. There were also nine vallate papillae and pair of foliate papillae. The foliate papillae contained several folds parted by 12–14 grooves. The mucous secretion produced by the lingual glands was more obvious than the serous secretion. The features of the dorsal surface of the tongue as well as the shape and number of the lingual papillae on the surface of the tongue of the examined female tapir differ compared to Equidae or Rhinocerotidae, the other two representatives of Perissodactyla. However, further study is necessary for the synapomorpy of the tapir’s tongue.

Chewing, dental morphology and wear in tapirs (Tapirus spp.) and a comparison of free-ranging and captive specimens

Feeding practice in herbivorous mammals can impact their dental wear, due to excessive or irregular abrasion. Previous studies indicated that browsing species display more wear when kept in zoos compared to natural habitats. Comparable analyses in tapirs do not exist, as their dental anatomy and chewing kinematics are assumed to prevent the use of macroscopic wear proxies such as mesowear. We aimed at describing tapir chewing, dental anatomy and wear, to develop a system allowing comparison of free-ranging and captive specimens even in the absence of known age. Video analyses suggest that in contrast to other perissodactyls, tapirs have an orthal (and no lateral) chewing movement. Analysing cheek teeth from 74 museum specimens, we quantified dental anatomy, determined the sequence of dental wear along the tooth row, and established several morphometric measures of wear. In doing so, we showcase that tapir maxillary teeth distinctively change their morphology during wear, developing a height differential between less worn buccal and more worn lingual cusps, and that quantitative wear corresponds to the eruption sequence. We demonstrate that mesowear scoring shows a stable signal during initial wear stages but results in a rather high mesowear score compared to other browsing herbivores. Zoo specimens had lesser or equal mesowear scores as specimens from the wild; additionally, for the same level of third molar wear, premolars and other molars of zoo specimens showed similar or less wear compared specimens from the wild. While this might be due to the traditional use of non-roughage diet items in zoo tapirs, these results indicate that in contrast to the situation in other browsers, excessive tooth wear appears to be no relevant concern in ex situ tapir management.

Comparative selective retention of particle size classes in the gastrointestinal tract of ponies and goats

There is a discrepancy in the literature on potential digesta separation mechanisms in horses, with both a selective retention of fine and of large particles postulated in different publications. To assess the net effect of such mechanisms, we fed ponies on a hay-only diet a pulse dose of whole (unchopped) marked hay together with a solute marker, collected faeces on a regular basis, measured marker concentrations in whole faeces and in their large (2.0-16 mm), medium (0.5-1.0 mm) and small (0.063-0.25 mm) particle fraction, and calculated the corresponding mean retention times (MRTs). For comparison, the same experiment was performed in goats. In goats, as expected, MRT_solute (35 hr) was significantly shorter than MRT_particle (51 hr); only a very small fraction of particle marker was excreted as large particles (2%); and the MRT of these large particles was significantly shorter than that of small particles (with a relevant difference of 8.6 hr), indicating that those few large particles that escape the rumen do so mostly soon after ingestion. In ponies, MRT_solute (24 hr) did not differ from MRT_particle (24 hr); a higher fraction of particle marker was excreted as large particles (5%); and the MRT of these large particles was longer than that of small particles (but with a non-relevant difference of less than 1 hr). These results indicate that no relevant net separation of digesta phases occurs in horses and that selective particle retention mechanisms in the large intestine are unlikely to represent important characteristics of the horse's digestive physiology.

Feeding Asian pangolins: An assessment of current diets fed in institutions worldwide

Pangolins are ant specialists which are under intense threat from the illegal wildlife trade. Nutrition has notoriously been their downfall in captivity and is still an issue in regards to rescue and rehabilitation. We analyzed the nutrient content of diets used by institutions that are successfully keeping Asian pangolins and to assess the variety of the ingredients and nutrients, compared these with the nutritional requirements of potential nutritional model species. We performed intake studies at five institutions and also had data from three other institutions. We also analyzed five different wild food items to use as a proxy of wild diet. We observed two categories of captive diets: those mostly or completely composed of insects and those high in commercial feeds or animal meat. Nutrient values were broad and there was no clear rule. The non-protein energy to protein energy ratio of the diets were much higher than the wild food items, more so for those which receive less insects. The average contribution of carbohydrate, fat and protein energy were also further away from the wild samples the less insects they contained. The previously suggested nutritional model for pangolins is the domestic dog which is supported by our relatively large nutrient ranges of apparently successful diets, however due to their highly carnivorous nature; the upper most nutrient intake data are not consistent with this and favor the feline nutrient recommendations. We are unable to render a conclusion of what model is more appropriate based on our data collected.