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Sponheimer et al 2019 Dietary Evolution
Abstract
Giant pandas are specialized herbivores that digest little of the bamboo they consume. A new study argues that pandas, like carnivores, get most of their energy from protein, explaining their carnivore-like guts and poor digestion. This may have facilitated their ancestors' transition to herbivory.
... While digestive adaptations of bamboo lemurs have not been studied in detail so far, especially not on a bamboo-only diet (Campbell et al., 2002), there is ample information on pandas. Pandas lack many of the typical adaptations of mammalian herbivores, such as hypsodont teeth, cellulolytic microbiota, voluminous guts, long retention times resulting in high fibre digestibility and feedstuff utilisation, but appear as outliers among the herbivores due to their strategy of extremely poor digestion coupled with extremely high food intakes (reviewed in De Cuyper et al., 2020;Nie et al., 2019;Sponheimer et al., 2019). A hypothetical explanation for the fact that organisms lacking the typical herbivore adaptations can maintain a niche focussed on a plant, and this against putative competition from "true" herbivores, is that bamboo is a plant food that is less fermentable than most other plant foods (Sponheimer et al., 2019). ...
... Pandas lack many of the typical adaptations of mammalian herbivores, such as hypsodont teeth, cellulolytic microbiota, voluminous guts, long retention times resulting in high fibre digestibility and feedstuff utilisation, but appear as outliers among the herbivores due to their strategy of extremely poor digestion coupled with extremely high food intakes (reviewed in De Cuyper et al., 2020;Nie et al., 2019;Sponheimer et al., 2019). A hypothetical explanation for the fact that organisms lacking the typical herbivore adaptations can maintain a niche focussed on a plant, and this against putative competition from "true" herbivores, is that bamboo is a plant food that is less fermentable than most other plant foods (Sponheimer et al., 2019). This argument is based on a study comparing in vitro fermentation rates of bamboo versus several other forages in herbivores . ...
... Pandas seem to succeed with high intakes, short retention times, morphologic adaptations (thumb, teeth) (Dierenfeld et al., 1982) and might focus on protein digestion rather than fibre fermentation (Nie et al., 2019) or handle bamboo through a combination of all these adaptations (Sponheimer et al., 2019). However, how do herbivore species such as the Gayal, sika deer or lemur cope with bamboo? ...
Bamboo is an enigmatic forage, representing a niche food for pandas and bamboo lemurs. Bamboo might not represent a suitable forage for herbivores relying on fermentative digestion, potentially due to its low fermentability. To test this hypothesis, guinea pigs (n = 36) were used as model species and fed ad libitum with one of three forages (bamboo, lucerne, or timothy grass) in a fresh or dried state, with six individuals per group, for 3 weeks. The nutrient composition and in vitro fermentation profile of bamboo displayed low fermentation potential, i.e. high lignin and silica levels together with a gas production (Hohenheim gas test) at 12 h of only 36% of that of lucerne and grass. Although silica levels were more abundant in the leftovers of (almost) all groups, guinea pigs did not select against lignin on bamboo. Dry matter (DM) intake was highest and DM digestibility lowest on the bamboo forage. Total short-chain fatty acid levels in caecal content were highest for lucerne and lowest for grass and bamboo. Bamboo-fed guinea pigs had a lower body weight gain than the grass and lucerne group. The forage hydration state did not substantially affect digestion, but dry forage led to a numerically higher total wet gut fill. Although guinea pigs increased DM intake on the bamboo diet, the negative effects on fermentation of lignin and silica in bamboo seemed overriding. For herbivores that did not evolutionary adapt, bamboo as an exclusive food resource can be considered as inadequate.
Research highlights
Guinea pigs fed with poorly fermentable bamboo had a low body weight gain and low dry matter digestibility compared to grass- and lucerne-fed guinea pigs, which could not be overcome by increasing dry matter intake.
... This conclusion suggests they did not evolve the capability to modulate liver catabolic activity necessary to conserve protein when consuming low protein diets. However, others have questioned this view of the over-riding importance of protein in ursid diet selection [2][3][4] , particularly in giant pandas 5 . ...
... Relative to the suggestion that giant pandas are not well adapted to consuming the more omnivorous macronutrient proportions characteristic of the diets of other ursids 1 , captive giant pandas are often fed various combinations of bamboo and high-carbohydrate supplements that include rice, baby cereal, bread, beans, wheat, millet, apples, carrots, ground corn, sorghum, sugar cane, and sugar in addition to milk, eggs, vegetables, and various meats 5,32,33 . The dry matter of giant panda diets in five Chinese zoos in which successful reproduction occurred (i.e., Beijing Zoo, Chengdu Zoo, China Conservation and Research Center, Fuzhou Zoo, and Xian Zoo) averaged 11.6 ± 2.4% protein, 39.0 ± 13.6% neutral detergent fiber (NDF) or cell wall, 5.0 ± 2.0% fat, and 5.4 ± 0.6% ash 32 . ...
The eight species of bears world-wide consume a wide variety of diets. Some are specialists with extensive anatomical and physiological adaptations necessary to exploit specific foods or environments [e.g., polar bears ( Ursus maritimus ), giant pandas ( Ailuropoda melanoleuca ), and sloth bears ( Melursus ursinus )], while the rest are generalists. Even though ursids evolved from a high-protein carnivore, we hypothesized that all have become low-protein macronutrient omnivores. While this dietary strategy has already been described for polar bears and brown bears ( Ursus arctos ), a recent study on giant pandas suggested their macronutrient selection was that of the ancestral high-protein carnivore. Consumption of diets with inappropriate macronutrient profiles has been associated with increased energy expenditure, ill health, failed reproduction, and premature death. Consequently, we conducted feeding and preference trials with giant pandas and sloth bears, a termite and ant-feeding specialist. Both giant pandas and sloth bears branched off from the ursid lineage a million or more years before polar bears and brown bears. We found that giant pandas are low-protein, high-carbohydrate omnivores, whereas sloth bears are low-protein, high-fat omnivores. The preference for low protein diets apparently occurred early in the evolution of ursids and may have been critical to their world-wide spread.
... The panda species, two herbivorous Carnivora feeding mainly on bamboo, appear as visual outliers in the data collection, which is not unexpected. In spite of their strictly herbivorous diets, pandas show a variety of features typically not associated with herbivory, including simple digestive tracts and a microbiome not geared towards fibre fermentation (reviewed in Sponheimer et al., 2019). Greater pandas feeding on bamboo only show a dry matter digestibility of less than 20%, and compensate with a high dry matter intake (up to 6% BM), with a total gut clearance in less than 12 h (Dierenfeld et al., 1982). ...
... How pandas can maintain their dietary niche remains speculative. It has been suggested that this is linked to the very high abrasiveness of bamboo on composite teeth of typical herbivores and especially to the low digestibility of bamboo in fermentation systems (Xi et al., 2007), which make typical herbivores less competitive on bamboo than on other plant diets (Sponheimer et al., 2019). This scenario matches the observation that over evolutionary time, the diet niche of pandas has narrowed from a more varied to their current bamboo-only diet (Han et al., 2019). ...
The general observation that secondary consumers ingest highly digestible food and have simple short guts and small abdominal cavities intuitively results in the assumption that mammalian carnivores carry less digesta in their gut compared to herbivores. Due to logistic constraints, this assumption has not been tested quantitatively so far. In this contribution, we estimated the dry matter gut contents (DMC) for 25 of the order Carnivora (including two strictly herbivorous ones, the giant and the red panda) using the physical 'Occupancy Principle', based on a literature data collection on dry matter intake (DMI), apparent dry matter digestibility (aD DM) and retention time (RT), and compared the results to an existing collection for herbivores. Scaling exponents with body mass (BM) for both carnivores and herbivores were in the same range with DMI ~ BM0.75; aD DM ~ BM0; RT ~ BM0.11 and DMC ~ BM0.88. The trophic level (carnivore vs herbivore) significantly affected all digestive physiology parameters except for RT. Numerically, the carnivore DMI level reached 77%, the RT 32% and DMC only 29% of the corresponding herbivore values, whereas the herbivore aD DM only reached 82% of that of carnivores. Thus, we quantitatively show that carnivores carry less inert mass or gut content compared to herbivores, which putatively benefits them in predator-prey interactions and might have contributed to the evolution towards unguligradism in herbivores. As expected, the two panda species appeared as outliers in the dataset with low aD DM and RT for a herbivore but extremely high DMI values, resulting in DMC in the lower part of the herbivore range. Whereas the difference in DMI and DMC scaling in herbivores might allow larger herbivores to compensate for lower diet quality by ingesting more, this difference may allow larger carnivores not to go for less digestible prey parts, but mainly to increase meal intervals, i.e. not having to hunt on a daily basis.
... Some Pseudomonas strains, such as Pseudomonas putida, can produce lipases and proteases that take part in dairy and meat spoilage [54,55]. The ancestors of giant pandas were meat-eating carnivorans [56,57]. Considering Pseudomonas strains (Bin4_Pseudomonas, within the Pseudomonas putida clade) were common strains among carnivorans (bamboo-eating pandas, CA, and OC groups), we deduced that this feature in the gut microbiota might be one of the 'imprints' from the coevolution between the Carnivora and their gut microbiota. ...
Many studies highlight that host phylogeny and diet are the two main factors influencing the animal gut microbiota. However, the internal mechanisms driving the evolution of animal gut microbiota may be more complex and complicated than we previously realized. Here, based on a large-scale meta-analysis of animal gut microbiota (16s RNA gene data from approximately 1,800 samples; 108 metagenomes) across a wide taxonomic range of hosts, from invertebrate to vertebrate, we found high similarity in the gut microbial community (high proportion of Gammaproteobacteria (Pseudomonas)) of invertebrate insects and vertebrate bamboo-eating pandas (giant panda and red panda), which might be associated their plant-eating behavior and the presence of oxygen in the intestinal tract. A Pseudomonas strain-level analysis using 108 metagenomes further revealed that the response to either host niches or selection by the host might further lead to host-specific strains (or sub-strains) among the different hosts congruent with their evolutionary history. In this study, we uncovered new insights into the current understanding of the evolution of animals and their gut microbiota.
... By consuming both salmon and berries, brown bears optimize the protein:energy ratio such that it increases the rate of body mass gained by 72% compared to salmon-only diets 10 . Giant pandas are strict herbivores that increase dietary protein content by selectively consuming plant parts, but it is unclear whether dietary protein levels are similar to or exceed the lower levels consumed by other ursids 12,13 . Polar bears are strictly carnivorous on the sea ice, but they appear to preferentially consume the blubber of lipid-rich marine mammal prey which would reduce their protein intake below that of typical strict carnivores while maximizing energy intake 14 . ...
Studies of predator feeding ecology commonly focus on energy intake. However, captive predators have been documented to selectively feed to optimize macronutrient intake. As many apex predators experience environmental changes that affect prey availability, limitations on selective feeding can affect energetics and health. We estimated the protein:fat ratio of diets consumed by wild polar bears using a novel isotope-based approach, measured protein:fat ratios selected by zoo polar bears offered dietary choice and examined potential energetic and health consequences of overconsuming protein. Dietary protein levels selected by wild and zoo polar bears were low and similar to selection observed in omnivorous brown bears, which reduced energy intake requirements by 70% compared with lean meat diets. Higher-protein diets fed to zoo polar bears during normal care were concurrent with high rates of mortality from kidney disease and liver cancer. Our results suggest that polar bears have low protein requirements and that limitations on selective consumption of marine mammal blubber consequent to climate change could meaningfully increase their energetic costs. Although bear protein requirements appear lower than those of other carnivores, the energetic and health consequences of protein overconsumption identified in this study have the potential to affect a wide range of taxa.
Major threats to the Andean bear (Tremarctos ornatus) include habitat fragmentation and anthropogenic-caused mortality related to hunting and human–bear conflicts (HBC). The Andean bear is listed as vulnerable (VU) globally (Vélez-Liendo
and García-Rangel 2017), and also under Peruvian law, but conservation efforts are increasing. In Peru, these efforts are
synthesized under the National Conservation Plan for the Andean bear (Serfor 2016). The plan emphasizes the need to
raise awareness about its biology, ecology, and interactions with humans, in order to develop strategies for participatory
management. Specifically, it aims to address negative perceptions by local people triggered by the negative impact of
Andean bears on traditional economic activities, like cattle and maize production, sometimes prompting retaliatory hunting
(Amanzo et al. 2007; Figueroa et al. 2013; Figueroa 2013, 2015).
The giant panda ( Ailuropoda melanoleuca ) and red panda ( Ailurus fulgens ), two obligate bamboo feeders, have distinct phylogenetic positions in the order Carnivora. Bamboo is extraordinarily rich in plant secondary metabolites, such as allied phenolic and polyphenolic compounds and even toxic cyanide compounds. Here, the enrichment of putative cyanide-digesting gut microbes, in combination with adaptations related to morphology (e.g., pseudothumbs) and genomic signatures, show that the giant panda and red panda have evolved some common traits to adapt to their bamboo diet. Thus, here is another story of diet-driven gut microbiota in nature.
The carnivoran giant panda has a specialized bamboo diet, to which its alimentary tract is poorly adapted. Measurements of daily energy expenditure across five captive and three wild pandas averaged 5.2 megajoules (MJ)/day, only 37.7% of the predicted value (13.8 MJ/day). For the wild pandas, the mean was 6.2 MJ/day, or 45% of the mammalian expectation. Pandas achieve this exceptionally low expenditure in part by reduced sizes of several vital organs and low physical activity. In addition, circulating levels of thyroid hormones thyroxine (T4) and triiodothyronine (T3) averaged 46.9 and 64%, respectively, of the levels expected for a eutherian mammal of comparable size. A giant panda-unique mutation in the DUOX2 gene, critical for thyroid hormone synthesis, might explain these low thyroid hormone levels. A combination of morphological, behavioral, physiological, and genetic adaptations, leading to low energy expenditure, likely enables giant pandas to survive on a bamboo diet.
Copyright © 2015, American Association for the Advancement of Science.
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The giant panda evolved from omnivorous bears. It lives on a bamboo-dominated diet at present, but it still retains a typical carnivorous digestive system and is genetically deficient in cellulose-digesting enzymes. To find out whether this endangered mammalian species, like other herbivores, has successfully developed a gut microbiota adapted to its fiber-rich diet, we conducted a 16S rRNA gene-based large-scale structural profiling of the giant panda fecal microbiota. Forty-five captive individuals were sampled in spring, summer, and late autumn within 1 year. Significant intraindividual variations in the diversity and structure of gut microbiota across seasons were observed in this population, which were even greater than the variations between individuals. Compared with published data sets involving 124 gut microbiota profiles from 54 mammalian species, these giant pandas, together with 9 captive and 7 wild individuals investigated previously, showed extremely low gut microbiota diversity and an overall structure that diverged from those of nonpanda herbivores but converged with those of carnivorous and omnivorous bears. The giant panda did not harbor putative cellulose-degrading phylotypes such as Ruminococcaceae and Bacteroides bacteria that are typically enriched in other herbivores, but instead, its microbiota was dominated by Escherichia/Shigella and Streptococcus bacteria. Members of the class Clostridia were common and abundant in the giant panda gut microbiota, but most of the members present were absent in other herbivores and were not phylogenetically related with known cellulolytic lineages. Therefore, the giant panda appears not to have evolved a gut microbiota compatible with its newly adopted diet, which may adversely influence the coevolutionary fitness of this herbivore.
Importance:
The giant panda, an endangered mammalian species endemic to western China, is well known for its unique bamboo diet. Unlike other herbivores that have successfully evolved anatomically specialized digestive systems to efficiently deconstruct fibrous plant matter, the giant panda still retains a gastrointestinal tract typical of carnivores. We characterized the fecal bacterial communities from a giant panda population to determine whether this animal relies on its symbiotic gut microbiota to cope with the complex carbohydrates that dominate its diet, as is common in other herbivores. We found that the giant panda gut microbiota is low in diversity and highly variable across seasons. It also shows an overall composition typical of bears and entirely differentiated from other herbivores, with low levels of putative cellulose-digesting bacteria. The gut microbiota of this herbivore, therefore, may not have well adapted to its highly fibrous diet, suggesting a potential link with its poor digestive efficiency.
Digestive physiology has played a prominent role in explanations for terrestrial herbivore body size evolution and size-driven diversification and niche differentiation. This is based on the association of increasing body mass (BM) with diets of lower quality, and with putative mechanisms by which a higher BM could translate into a higher digestive efficiency. Such concepts, however, often do not match empirical data. Here, we review concepts and data on terrestrial herbivore BM, diet quality, digestive physiology and metabolism, and in doing so give examples for problems in using allometric analyses and extrapolations. A digestive advantage of larger BM is not corroborated by conceptual or empirical approaches. We suggest that explanatory models should shift from physiological to ecological scenarios based on the association of forage quality and biomass availability, and the association between BM and feeding selectivity. These associations mostly (but not exclusively) allow large herbivores to use low quality forage only, whereas they allow small herbivores the use of any forage they can physically manage. Examples of small herbivores able to subsist on lower quality diets are rare but exist. We speculate that this could be explained by evolutionary adaptations to the ecological opportunity of selective feeding in smaller animals, rather than by a physiologic or metabolic necessity linked to BM. For gigantic herbivores such as sauropod dinosaurs, other factors than digestive physiology appear more promising candidates to explain evolutionary drives towards extreme BM.
The goals of this study were to determine digestibility of a bamboo diet by giant pandas (Ailuropoda melanoleuca) and to evaluate potential internal markers (naturally occurring markers in their diet) for their ability to estimate fecal output and digestibility. Digestibility predictions using internal markers were based on either feed offered or feed consumed. Two giant pandas were used in 1-, 2-, and 3-day digestibility trials with total collection of feces. In the 3-day trial, animals were fed 100% bamboo with no dietary supplements. In all other trials, supplements were included in addition to bamboo. The 3 internal markers chosen for evaluation were acid insoluble ash (AIA), acid detergent lignin (ADL), and acid detergent insoluble nitrogen (ADIN). Results from digestibility trials indicated that apparent nutrient digestibility could be determined with no differences (P > 0.05) between pandas. Six apparent dry matter (DM) digestibility values ranged from 6.9 to 38.5%. Apparent DM digestibility for the male and female panda in the unsupplemented (3-day) trial were 6.9 and 12.4%, respectively. Among the 3 potential internal markers evaluated, AIA more accurately predicted fecal output (r = 0.99; P < 0.01) than ADL (r = 0.84; P < 0.02) or ADIN (r = 0.85; P < 0.02). Calculations using AIA and feed consumed more accurately predicted nutrient digestibility than did feed offered calculations for all 3 internal markers. Apparent crude protein (CP) digestibility was 33.8% and was predicted by AIA and feed consumed calculations to be 35.5% (r = 0.88; P = 0.009). Acid insoluble ash and feed consumed calculations predicted fiber digestibility to be 35.1% compared to apparent fiber digestibility (31.8%; r = 0.97, P < 0.001). Methods and data presented in this study may be used to predict nutrient digestibility in wild pandas in their native habitat.
We report feeding studies on adult domestic cats designed to disentangle the complex interactions among dietary protein, fat and carbohydrate in the control of intake. Using geometric techniques that combine mixture triangles and intake plots from the geometric framework, we: (1) demonstrate that cats balance their macronutrient intake, (2) estimate the composition of the target balance and (3) reveal the priorities given to different macronutrients under dietary conditions where the target is unachievable. Our analysis indicates that cats have a ceiling for carbohydrate intake, which limits ingestion and constrains them to deficits in protein and fat intake (relative to their target) on high-carbohydrate foods. Finally, we reanalyse data from a previous experiment that claimed that kittens failed to regulate protein intake, and show that, in fact, they did. These results not only add to the growing appreciation that carnivores, like herbivores and omnivores, regulate macronutrient intake, they also have important implications for designing feeding regimens for companion animals.
The circumstances of the evolution of hypsodonty (= high-crowned teeth) are a bone of contention. Hypsodonty is usually linked to diet abrasiveness, either from siliceous phytoliths (monocotyledons) or from grit (dusty environments). However, any empirical quantitative approach testing the relation of ingested silica and hypsodonty is lacking. In this study, faecal silica content was quantified as acid detergent insoluble ash and used as proxy for silica ingested by large African herbivores of different digestive types, feeding strategies and hypsodonty levels. Separate sample sets were used for the dry (n = 15 species) and wet (n = 13 species) season. Average faecal silica contents were 17-46 g kg(-1) dry matter (DM) for browsing and 52-163 g kg(-1) DM for grazing herbivores. No difference was detected between the wet (97.5 ± 14.4 g kg(-1) DM) and dry season (93.5 ± 13.7 g kg(-1) DM) faecal silica. In a phylogenetically controlled analysis, a strong positive correlation (dry season r = 0.80, p < 0.0005; wet season r = 0.74, p < 0.005) was found between hypsodonty index and faecal silica levels. While surprisingly our results do not indicate major seasonal changes in silica ingested, the correlation of faecal silica and hypsodonty supports a scenario of a dominant role of abrasive silica in the evolution of high-crowned teeth.
Two giant pandas were used to assess the utilization of bamboo as a feedstuff. Three 1-week-long digestion trials were conducted during which feed intake and fecal output were recorded. Passage of digesta was measured from both fluid and particulate markers administered at feeding. Results indicate that the giant panda, although highly specialized for the consumption of bamboo, is a very inefficient digester of bamboo. The pandas consumed up to 6% of body weight in dry matter per day, with bamboo dry matter digestibility averaging less than 20%. Apparent digestion coefficients for the structural carbohydrates of bamboo (27% for hemicellulose and 8% for cellulose) indicate that, unlike most herbivores, pandas do not rely heavily on the microbial degradation of plant material to fulfill their nutritional requirements. Additionally, the passage of digesta through the gastrointestinal tract of the panda was extremely rapid, with complete clearance of markers in less than 12 hours. The giant panda seems to have specialized to a feed source high in plant fiber without extensive modification of the digestive tract by selectivity in feeding, effective mastication, ingestion of large quantities, digestion of cellular contents rather than cell walls and rapid fecal excretion of the undigested residue.
Giant pandas are unusual in belonging to a primarily carnivorous clade and yet being extremely specialized herbivores that feed almost exclusively on highly fibrous bamboo [1]. Paradoxically, they appear inconsistently adapted to their plant diet, bearing a mix of herbivore and carnivore traits. Herbivore traits include a skull, jaw musculature, and dentition that are adapted for fibrous diets and a specialized "pseudo-thumb" used for handling bamboo [2, 3]. They have lost functional versions of the T1R1 gene codes for umami taste receptors, which are often associated with meat eating [3]. They also have an herbivore-like subcellular distribution of the metabolic enzyme alanine: glyoxylate aminotransferase [4]. But meanwhile, giant pandas have a digestive tract [5], digestive enzymes [6], and a gut microbiota composition that resemble those of carnivores and not of herbivores [6, 7]. We draw on recent developments in multi-dimensional niche theory [8] to examine this apparent paradox. We show that the pandas' diet clustered in a macronutrient space among carnivores and was distinct from that of herbivores. The similarity with carnivore diets applied not only to the ingested diet but also to the absorbed diet, with the absorbed macronutrient ratios similar to those of the ingested foods. Comparison of the macronutrient composition of pandas' milk with those of other species shows that the carnivore-like dietary macronutrient composition extends across the life cycle. These results cast new light on the seemingly incongruous constellation of dietary adaptations in pandas, suggesting that the transition from carnivorous and omnivorous ancestry to specialized herbivory might be less abrupt than it might otherwise appear.
The dietary generalist-specialist distinction plays a pivotal role in theoretical and applied ecology, conservation, invasion biology, and evolution and yet the concept remains poorly characterised. Diets, which are commonly used to define niche breadth, are almost exclusively considered in terms of foods, with little regard for the mixtures of nutrients and other compounds they contain. We use nutritional geometry (NG) to integrate nutrition with food-level approaches to the dietary niche and illustrate the application of our framework in the important context of invasion biology. We use an example that involves a model with four hypothetical nonexclusive scenarios. We additionally show how this approach can provide fresh theoretical insight into the ways nutrition and food choices impact trait evolution and trophic interactions.
Many animals consume mixed diets that maximize their fitness by optimizing macronutrient intake. We tested whether brown bears (Ursus arctos), generalist omnivores that hibernate, regulated their diet to a common nutrient target, achieved a nutrient target related to fitness, and selected a nutrient target that differed between seasons and from other species with differing life histories. When given unlimited access to 2 or 3 highly digestible foods containing primarily protein, carbohydrate, or lipid, brown bears selected mixed diets in which protein provided 17% +/- 4% SD of the metabolizable energy and 22% +/- 6% of the dry matter. This dietary protein content maximized the rate of gain per unit of energy consumed, is similar to the level preferred by other omnivores, and is less than that preferred by obligate carnivores. Between seasons, bears selected similar dietary protein levels, although the proportion of lipid was higher during the fall than during the spring. Bears strongly preferred lipids over carbohydrates, as did other carnivores, but they used lipids and carbohydrates with equal efficiency to produce a dietary protein content that maximized mass gain per unit of energy intake. Thus, dietary sources of lipids and carbohydrates play an interchangeable and important role in determining the productivity of bears that goes beyond their role in providing energy.
Structural carbohydrates in plants are hard to digest by the animals that eat them, and they ham-per digestion of the content of the plant cells. The efficiency of digestion by herbivores is, there-fore, closely related to both the retention time of the food in the digestive tract and the propor-tion of cell walls in the food. This study examined food digestion by free-living barnacle geese Branta leucopsis in relation to food quality and retention time. At the range of short winter days (8 h light) to continuous light in the Arctic breeding area, the geese increased the food retention time 2-4-fold. Low throughput rates in summer resulted in enhanced digestion of the food. The organic matter digestibility of graminoids, corrected for dif-ferences in protein content, was 37% in winter, and 56% in summer. Enhanced digestion allowed the geese to extend their food spectrum by exploiting mosses (bryophytes), which are, at least temporarily, the only plants available in the summer range. The disadvantage of prolonged food retention time is the concurrent decrease of the amount of food that can be processed per time unit. The digestion pattern in the successive periods of the year can be regarded as an adaptation to differences in energy needs, and to differences in the selective force acting on the geese to mini-mize feeding time.
Three male Gayal, two years of age and with a mean live weight of 203?26 kg, and three adult Yunnan Yellow Cattle, with a mean live weight of 338?18 kg were fed a ration of pelleted lucerne hay and used to collect rumen fluid for in vitro measurements of digestibilities and gas production from fermentation of a range of forages. The forages were: bamboo stems, bamboo twigs, bamboo leaves, rice straw, barley straw, annual ryegrass hay, smooth vetch hay and pelleted lucerne hay. There were significant (p
Two digestion trials by total feces collection method were conducted, using a male adult giant panda in captivity fed feedstuffs including bamboo. Collected pieces of feces were assorted according to undigested feedstuff mainly forming each piece of feces, and analyzed separately. The data were converted into undigested nutrients of each feedstuff with a calculating procedure devised to assess respective digestibility. Cell wall constituents of bamboo were apparently digested to a certain extent, although the digestibility was low (24.1% and 15.0% in Experiment 1 and 2, respectively, in the case of NDF (neutral detergent fiber)). Cellular contents of the bamboo were also less digestible compared with those of the other feedstuffs, while nutrients in less fibrous feedstuffs (concentrates) were digested fairly well (more than 90%). The amount of non structural carbohydrate of bamboo excreted in the feces, exceeded the amount ingested. This fact was considered to be due to imperfect digestion of cell wall constituents, resulting matters soluble in the detergent but not absorbed. Regarding the importance of ingesting sufficient bamboo not only for supplying nutrients but also for supporting sound digestive conditions in the panda was discussed.
The aim of this study was to understand the mandible of the giant panda in morphometric terms to explore differences between the giant panda and other carnivores distributed in China, in terms of functional adaptation. Twelve mandibular variables were studied using bivariate (allometry) and multivariate (principal components analysis, PCA, and discriminant functional analysis, DFA) tools. When deviations were produced from allometric baselines consisting of all the species studied, the giant panda displayed a much more developed mandibular structure than the bear, leopard, and tiger. This may be related to its specific dietary preference for bamboo, which has very strong fibers. Results also indicate that the mandibular structure among carnivores mainly reflects the differences in their dietary preferences and functional adaptation. Three groups were found referring to dispersal profiles expressed by the first two axes of PCA and DFA: (1) the two panda species – the herbivorous carnivores; (2) the black bear – the omnivorous carnivore; and (3) the tiger and leopard – the hypercarnivores. Nevertheless, a significant separation between the two panda species was also found with the profiles displayed by the first and third axes of DFA. In addition to no close evolutionary relationship and phylogenetic development, a noticeable separation between the two panda species found in DFA analysis may be associated with their variation in consuming different parts of the bamboo plant: the giant panda feeds on stems and the red panda feeds on leaves. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 92, 449–456.
Information on diets fed to captive giant pandas in five Chinese facilities (Beijing Zoo, Chengdu Zoo, China Conservation and Research Center, Fuzhou Zoo, and the Xian Zoo for the Giant Panda) in which pandas have successfully reproduced was compiled from publications and/or personal communications. Each facility feeds a steamed grain mixture comprising 13–56% of the diet on an as-fed basis, animal products (milk, eggs, and/or meat; 8–25% of the diet), and bamboo (17–82% of the diet). Seasonally available fruits and/or vegetables are sometimes included (0–29% of the diet). Typically, bamboo is offered throughout the day in small increments, while the remaining diet (concentrate portion) is fed in two meals. Despite the variety of ingredients in the concentrate recipes among institutions, there was remarkable similarity in nutrient composition: 55–65% water, 13–19% crude protein (CP), 2.5–4.0% crude fat (CF), and 2–5% ash (Ca, 0.2–0.9%; P, 0.4–0.8%) (all nutrients except water expressed on a dry matter (DM) basis). Calculated digestible energy content averaged about 3.3 kcal/kg DM. With the addition of animal products, bamboo, and produce, total diet composition averaged 51% water and, on a DM basis, 12% CP, 5.0% CF, 20–57% NDF (fiber), 0.5% Ca, 0.4% P, and 50–150 mg/kg vitamin E. These specifications are similar to nutrient requirements established for domestic canids and would appear adequate to meet the (as yet unestablished) requirements of the giant panda in captivity. Formulations for mineral and vitamin supplements to balance concentrate portions of these basic diets are included. © 1995 Wiley-Liss, Inc.
Ant- and termite-eating are among the few food habits common to monotremes, marsupials, and eutherians. Data are reported on the rate of metabolism and temperature regulation of 14 species of mammals having these food habits, including two monotremes, one marsupial and 11 eutherians. Small mammals with these habits have comparatively high body temperatures and high basal rates of metabolism, but ant- and termite-eaters that weigh more than 1 kg generally have low body temperatures and low basal rates of metabolism. The higher basal rates in small species ensure effective temperature regulation. Low body temperatures in large species principally result from low rates of metabolism. Rates of metabolism are low in these mammals because they use a food that has a limited availability and a low energy density, the density being further decreased in large species by the ingestion of non-nutritive material during feeding. Burrowing habits in some large species also contribute to low rates of metabolism. The combination of body size, food habits, and presence or absence of burrowing behaviour can account for all but about 6% of the range in basal rate in ant- and termite-eaters. Ants and termites, because of their locally clumped distributions, permit a larger mass in terrestrial predators than do other invertebrate prey. The reason why so many “primitive” mammals feed on ants and termites is that, once evolved, mammals with these habits are nearly impossible to displace ecologically, because much of ecological replacement is associated with high rates of reproduction, which are themselves correlated with high rates of metabolism in eutherians. Consequently, the ecological replacement of ant- and termite-eaters is inhibited, because this food habit does not permit high rates of metabolism, except at small masses.