Harvesting, rumination, digestion, and passage of fruit and leaf diets by a small ruminant, the blue duiker

Because small ruminants (<15 kg) have a high ratio of metabolic rate to fermentation capacity, they are expected to select and require low-fiber, nutrient-dense concentrate diets. However, recent studies suggest that small ruminants may not be as limited in their digestive capacity as previously thought. In this study, we examined harvesting, rumination, digestion, and passage of three diets (domestic figs Ficus carica, fresh alfalfa Medicago sativa, and Pacific willow leaves Salix lasiandra) ranging from 10 to 50% neutral detergent fiber content (NDF) in captive blue duikers (Cephalophus monticola, 4 kg). Harvesting and rumination rates were obtained by observing and videotaping animals on each diet, and digestibility and intake were determined by conducting total collection digestion trials. We estimated mean retention time of liquid and particulate digesta by administering Co-EDTA and forages labelled with YbNO₃ in a pulse dose and monitoring fecal output over 4 days. Duikers harvested and ruminated the fig diet faster than the alfalfa and willow diets. Likewise, they achieved higher dry matter, energy, NDF, and protein digestibility when eating figs, yet achieved a higher daily digestible energy intake on the fresh willow and alfalfa than on the figs by eating proportionately more of these forages. Duikers maintained a positive nitrogen balance on all diets, including figs, which contained only 6.3% crude protein. Mean retention time of cell wall in the duikers’ digestive tract declined with increasing NDF and cellulose content of the diet. Digestibility coefficients and mean retention times of these small ruminants were virtually equivalent to those measured for ruminants two orders of magnitude larger, suggesting that they are well adapted for a mixed diet. Received: 10 August 1999 / Accepted: 16 November 1999     

Voluntary intake and digestibility in horses: effect of forage quality with emphasis on individual variability

Food intake is a key biological process in animals, as it determines the energy and nutrients available for the physiological and behavioural processes. In herbivores, the abundance, structure and quality of plant resources are known to influence intake strongly. In ruminants, as the forage quality declines, digestibility and total intake decline. Equids are believed to be adapted to consume high-fibre low-quality forages. As hindgut fermenters, it has been suggested that their response to a reduction in food quality is to increase intake to maintain rates of energy and nutrient absorption. All reviews of horse nutrition show that digestibility declines with forage quality; for intake, however, most studies have found no significant relationship with forage quality, and it has even been suggested that horses may eat less with declining forage quality similarly to ruminants. A weakness of these reviews is to combine data from different studies in meta-analyses without allowing the differences between animals and diets to be controlled for. In this study, we analysed a set of 45 trials where intake and digestibility were measured in 21 saddle horses. The dataset was analysed both at the group (to allow comparisons with the literature) and at the individual levels (to control for individual variability). As expected, dry matter digestibility declined with forage quality in both analyses. Intake declined slightly with increasing fibre contents at the group level, and there were no effects of crude protein or dry matter digestibility on intake. Overall, the analysis for individual horses showed a different pattern: intake increased as digestibility and crude protein declined, and increased with increasing fibre. Our analysis at the group level confirms previous reviews and shows that forage quality explains little of the variance in food intake in horses. For the first time, using mixed models, we show that the variable 'individual' clarifies the picture, as the horses showed different responses to a decrease in forage quality: some compensated for the low nutritional value of the forages by increasing intake, few others responded by decreasing intake with declining forage quality, but not enough to cause any deficit in their energy and protein supplies. On the whole, all the animals managed to meet their maintenance requirements. The individual variability may be a by-product of artificial selection for performance in competition in saddle horses.     

Chemical composition of the water fern,salvinia molesta,and its potential as feed source for ruminants

The chemical composition of the now widespread tropical aquatic fern Salvinia molestawas analysed with regard to its suitability as a source of forage for ruminants. Three different stages of plant growth collected in Kerala, India, were air dried, brought to Germany, and used for Weende analysis, detergent fibre analysis, and the determination of gross energy, amino acids, tannins, and minerals. The concentration of 12.4% crude protein in sand-corrected dry matter (DM) and of some other nutrients in Salviniais comparable to that in conventional forage. However, the high content of crude ash (17.3% in DM) and of lignin (13.7%) and the presence of tannins (0.93%) may reduce acceptance as well as digestibility and therefore restrict the use of Salviniaas a potential feed source for ruminants.     

Digestibility, nitrogen excretion, and mean retention time by North American porcupines (Erethizon dorsatum) consuming natural forages

North American porcupines (Erethizon dorsatum) subsist predominantly on low-protein, high-fiber, high-tannin diets. Therefore, we measured the porcupine's ability to digest dry matter, fiber, and protein by conducting digestion trials on eight natural forages and one pelleted ration varying in concentration of fiber, nitrogen, and tannins. On these diets, dry matter intake ranged from 5 to 234 g/kg(0.75)/d and dry matter digestibility ranged from 62% to 96%. Porcupines digested highly lignified fiber better than many large hindgut fermenters and ruminants. The porcupine's ability to digest fiber may be explained, in part, by their lengthy mean retention time of particles (38.43+/-0.56 h). True nitrogen digestibility was 92% for nontannin forages and pellets. Endogenous urinary nitrogen was 205 mg N/kg(0.75)/d, and metabolic fecal nitrogen was 2.8 g N/kg dry matter intake. Porcupines achieved nitrogen balance at relatively low levels of nitrogen intake (346 mg N/kg(0.75)/d). Tannins reduced the porcupines' ability to digest protein. However, the reduction in protein digestion was not predictable from the amount of bovine serum albumin precipitated. Like many herbivores, porcupines may ameliorate the effects of certain tannins in natural forages on protein digestibility through physiological and behavioral adaptations.     

Nutritional Values of 14 Fig Species and Bat Feeding Preferences in Panama1

Figs are a critical resource for many tropical frugivores, yet they often are referred to as low quality fruits. To determine their nutritional value, both as a group and for individual species, we analyzed 14 fig species from Barro Colorado Island (BCI), Panama, for fiber, tannins, lipids, protein, carbohydrates, amino acids, and minerals. Seeds and pulp were analyzed separately. Fig fruit pulp consisted of about one‐third digestible components, mostly carbohydrates with some lipids and proteins. Tannin, lignin, and water‐soluble carbohydrates showed considerable variation among species, as did fruit size. Figs contained high amounts of amino acids, such as leucine, lysine, valine, and arginine, and minerals, such as potassium, calcium, magnesium, sodium, and phosphorus. One species, Ficus insipida, contained the highest concentrations of almost all amino acids, many minerals, and protein. Small figs had as much nutritional value per gram as large figs. Free‐standing figs had higher percentages of protein, complex carbohydrates, and ash than strangler figs, which had higher percentages of water‐soluble carbohydrates, tannins, and hemicellulose. The guild of fruit‐eating bats on BCI included ten common species with diets dominated by figs. Fecal analyses and captures at ripe fig trees showed a consistent pattern of resource partitioning. Small bats preferentially ate small‐fruited and strangler figs while large bats consumed mostly large‐fruited and free‐standing figs. Small bats most often ate F. bullenei, which has high levels of lipid and carbohydrates, and F. yoponensis, which has high levels of protein. Medium and large bats most often ate F. insipida, a nutritionally superior species; their second most eaten species was F. obtusifolia, in which the large size may make it efficient to eat. Each bat ate a variety of fig species, supporting the idea that although no single species of fig may be sufficient to sustain frugivores, a mix of fig species can provide a complete set of nutrients.     

A Noninvasive Method for Estimating Nitrogen Balance in Free-Ranging Primates

The vital role of body protein as an energy reserve has received little focus in studies of wild primates. Owing to the relatively low protein content of fruit, some frugivorous primates could face a protein deficit if body protein is catabolized for energy during periods of low fruit availability. Such an imbalance can be detected if fatty acids, amino acids, and nitrogen (N) catabolites are reincorporated or recycled back to tissues. Here we describe a method to quantify protein recycling by measuring standardized urea concentration and N isotope signatures from urine samples collected from wild Bornean orangutans (Pongo pygmaeus wurmbii). Our overall goal was to explore if concentrations of urea and ??¹⁵N values could be used as indicators of the amount of protein consumed and the degree of protein recycling, respectively, in wild, free-ranging primates. We examine the relationships between urea concentration, ??¹⁵N values, protein intake, and fruit availability. Urea concentration increased with fruit availability, reflecting a slight increase in protein consumption when fruit was abundant. However, we found no relationship between ??¹⁵N values and fruit availability, suggesting that orangutans avert a negative protein balance during periods of low fruit availability. These noninvasive methods complement recent advances in primate energy balance research and will contribute to our understanding of adaptations of primates during periods of fruit shortage.     

The influence of fibre in the diet on growth rates and the digestibility of nutrients in the greater cane rat (Thryonomys swinderianus).

The greater cane rat Thryonomys swinderianus is a coprophagous rodent in which fermentation occurs in the large caecum. The extent to which a 45% increase in the fibre component of the diet influenced growth rates of cane rats and the digestibility of nutrients and energy was investigated in two feeding trials. Higher fibre levels in the diet reduced the digestibility of dry matter, protein and fat, while animals digested fibre components (neutral-detergent fibre, acid detergent fibre, hemicellulose and cellulose) with a comparable efficiency to those maintained on a low fibre diet. In one of the trials animals fed the high fibre diet exhibited significantly lower growth rates than animals fed the low fibre diet. Digestibility coefficients of the cane rats for neutral-detergent fibre and protein seem to be intermediate to high when compared to reported values for the porcupine, guinea-pig, degu and rabbit. It is suggested that the ability of cane rats to utilise large quantities of fibre enable them to survive periods when only dry grass is available.     

Small ruminants: Digestive capacity differences among four species weighing less than 20 kg

Small ruminants are generally classified as either browsers or frugivores. We compared intake and digestion in one browsing species, the pudu (Pudu pudu), body weight 9 kg, and three frugivorous species, the red brocket (Mazama americana), 20 kg, the bay duiker (Cephalophus dorsalis), 12 kg, and Maxwell's duiker (C. maxwellii), 9 kg. Rations comprised: a commercial grain and alfalfa pellet, a small amount of vegetables, and mixed hay. Across species, neutral-detergent fiber (insoluble fiber) consumed averaged 34.2 ± 2.6% of dry matter (DM) while the crude protein consumed averaged 16.1 ± 0.5% DM. Apparent DM digestion was similar in pudu (75.2 ± 4.7%), brocket (73.2 ± 1.1%), and Maxwell's duikers (73.0 ± 2.8%), and significantly lower (P = 0.0167) in bay duikers (67.1 ± 4.3%). There were significant differences among species in digestibilities of neutral-detergent fiber, hemicellulose, and cellulose, but they did not follow body size differences, since larger species were expected to show higher digestion coefficients for fiber compared to smaller species. The type of fiber fed may have influenced these results. Frugivores may be adapted to a diet of soluble fibers, as might be found in wild fruits, instead of the insoluble fibers in the diet fed. Passage trials were conducted on the two smallest species. The mean transit time for pudu was 29.9 ± 0.8 hr, and for the Maxwell's duiker was 42.2 ± 6.4 hr. © 1996 Wiley-Liss, Inc.     

More efficient mastication allows increasing intake without compromising digestibility or necessitating a larger gut: Comparative feeding trials in banteng (Bos javanicus) and pygmy hippopotamus (Hexaprotodon liberiensis)

The digestion of plant material in mammalian herbivores basically depends on the chemical and structural composition of the diet, the mean particle size to which the forage is processed, and the ingesta retention time. These different factors can be influenced by the animal, and they can presumably compensate for each other. The pygmy hippopotamus, a non-ruminating foregut fermenter, has longer mean retention times than ruminants; however hippos do not achieve higher (fibre) digestibilities on comparable diets, which could be due to ineffective mastication. We performed feeding trials with six pygmy hippos (Hexaprotodon liberiensis) and six banteng cattle (Bos javanicus) on a grass diet. As predicted, both species achieved similar dry matter, organic matter, crude protein and gross energy digestibilities. However, neutral and acid detergent fibre digestibility was lower in pygmy hippos. Apparently, in these species, fibre digestibility was more influenced by particle size, which was larger in pygmy hippos compared to banteng, than by retention time. In spite of their higher relative food intake, the banteng in this study did not have greater relative gut fills than the hippos. Ruminants traditionally appear intake-limited when compared to equids, because feed particles above a certain size cannot leave the rumen. But when compared to nonruminating foregut fermenters, rumination seems to free foregut fermenters from an intrinsic food intake limitation. The higher energy intakes and metabolic rates in wild cattle compared to hippos could have life-history consequences, such as a higher relative reproductive rate.     

Monitoring nutrition in small ruminants with the aid of near infrared reflectance spectroscopy (NIRS) technology: A review

This review aims to evaluate the contribution of near infrared reflectance spectroscopy (NIRS) to monitor nutrition in small ruminants, with particular emphasis on the use of feed spectra and fecal spectra. NIRS provides satisfactory accuracy in the analysis of the chemical constituents of feeds for small ruminants, e.g., crude protein and cell wall composition, and is sometimes better than in vitro procedures for predicting in vivo digestibility and the available energy in feeds. In addition, in vitro digestibility can be accurately estimated by NIRS. The effective rumen degradability of protein could potentially be accurately predicted by NIRS, which would eliminate the need for rumen-fistulated animals. Good accuracy in the prediction of tannins has been reported for narrow, single-species applications, as well as for broad arrays of browse species. The identification of NIR segments corresponding to undigested entities has potential to help in providing spectral markers of digestibility. Fecal output can easily be evaluated, using the NIRS-aided analysis of polyethylene glycol (PEG) administered as external indigestible marker. Analysis of NIR spectra of the feces enables the accurate prediction of the chemical characteristics of the feed (dry matter digestibility and crude protein, cell wall attributes, PEG-binding tannins) in stall-fed and grazing animals, and to some extent, of the botanical composition of diets at pasture. Thus, fecal NIRS methodology holds the potential to provide nutritional diagnoses for farmers raising small ruminant.     

Tannins and digestibility in the steenbok (Raphicerus campestris)

1. The influence of tannins on the digestion of a small ruminant was investigated. 2. A 1% tannic acid diet was compared with a normal diet. 3. The digestion of protein decreased by 7.04%, fibre by 9.77% and energy utilization decreased by 7.94%. 4. Tannic acid has a marked depressing effect on the digestibility of the steenbok.     

The nutritional significance of endogenous n‐losses along the gastrointestinal tract of farm animals

In animal production, endogenous protein losses associated with the digestion process are important losses, but difficult to measure. Measuring methods include feeding N‐free diets, regression techniques based on amino acid profiles, and separating feed protein and endogenous protein by markers like homoarginine, hydrolysed casein or stable isotopes like ¹⁵N. Endogenous losses arise from saliva, digestive enzymes, bile, shedded epithelial cells and mucins and may be extra stimulated by the presence in feeds of antinutritional factors (ANF) such as lectins, trypsin inhibitors (TI), tannins and fibre. The impact of such factors may differ between non‐ruminants and ruminants. The magnitude of the effect of the different factors is quantified and some of the consequences for protein deposition and nitrogen losses to the environment are discussed.     

Effects of tannins on digestion in the common ringtail possum (Pseudocheirus peregrinus), a specialized marsupial folivore

Digestibility trials using common ringtail possums ( Pseudocheirus peregrinus ), small folivorous marsupials, were used to determine effects of tannins on a herbivore which has a specialized hind gut and which normally consumes tannin-rich eucalypt leaves. In one group, untreated leaves were fed to possums, and in a second group polyethylene glycol (PEG) was added to the eucalypt leaves to inactivate tannins. Animals maintained weight, and intakes were not different between the two dietary groups. Digestibility was determined chemically. Digesta were examined histologically. The presence of bacterial rafts in the stomachs of possums fed either diet indicated that PEG did not alter the coprophagic behaviour of possums. Cell wall digestion did not appear to be inhibited by tannins. Tanning of cell contents was predominant, rather than tanning of cell walls. PEG increased faecal excretion of tannins, suggesting that some tannins from normal leaves were digested during gut passage. Dry matter digestibility was higher when animals were fed normal tannin-rich leaves than when they were fed leaves in which tannins were inactivated. The difference could be explained in part by the high digestibility of tannins. The presence of tannin did not reduce nitrogen digestion. We suggest that dissociation of tannin-protein complexes may take place in the specialized caecum. We propose that some other folivorous marsupials may have a similar capacity to overcome tannins. This capacity may allow them to consume a tannin-rich diet.     

The digestion of dietary protein bound by condensed tannins in the gastro-intestinal tract of sheep

The digestion of dietary protein bound by condensed tannins (CTs) in ruminants was investigated by determining the extent of dissociation of insoluble ¹²⁵I-BSA + CT complexes administered to abomasally and intestinally fistulated sheep. The extent of dissociation was registered as the true digestibility of iodinated bovine serum albumin (¹²⁵I-BSA). The true digestibility of ¹²⁵I-BSA originally bound to Leucaena pallida CT (0.721) was lower (P<0.05) than that of ¹²⁵I-BSA originally bound to L. leucocephala CT (0.880) between the abomasum and terminal ileum. These results indicate that differences in the ability of CT to inhibit ¹²⁵I-BSA digestion in vivo matched the relative abilities of the same CT to bind BSA in vitro, indicating that the in vitro BSA-binding assay for ranking CT behaviour was biologically relevant in vivo. Furthermore, the true digestibility of CT-bound ¹²⁵I-BSA between the mouth and faeces permitted the prediction of the quantitative contribution that CT-bound dietary proteins make to improved nitrogen supply to the small intestines.     

Fruit size in wild olives: implications for avian seed dispersal

1. The response of frugivorous birds to an enlargement of fruit size, and the consequences for both birds and plants, are analysed for the interaction between avian seed dispersers and olives ( Olea europaea) .
2. The enlargement of fruit size promotes a shift in frugivorous birds' feeding behaviour, from swallowing fruits whole to pecking pieces of pulp. The relative frequency of olive consumption using each feeding behaviour was assessed by combining field data on frequency of appearance of olive pulp and seeds with data from laboratory trials.
3. Sardinian Warblers ( Sylvia melanocephala ) and European Robins ( Erithacus rubecula ) were mainly peckers both on cultivated and wild olives. Blackcaps ( Sylvia atricapilla ) consumed wild olives mainly by swallowing but consumed cultivated olives (larger than the wild ones) primarily by pecking. Song Thrushes ( Turdus philomelos ) were primarily swallowers of both types of fruits.
4. Laboratory trials with Song Thrushes, Blackcaps and European Robins showed that: (a) all were able to peck fruits; (b) fruit size determined a shift from swallowing to pecking, as pecking frequency increased with the enlargement of the fruit size; (c) all the species had an increased fruit handling failure rate when trying to swallow increasingly large fruits; and (d) from the birds' perspective, small shifts in fruit size may have important consequences on fruit profitability.
5. Pecking on olives turns the mutualistic fruit–frugivore interaction into a fruit-pulp predator interaction, thus arising a conflict between the plant and frugivorous birds.
6. This study shows that heavy dependence on fruit is not always simply related to seed dispersal. The same frugivorous bird species can act as a seed disperser or a pulp predator for the same plant species. The threshold between these roles is highly influenced by the ratio gape size/fruit size.     

Using stable isotopes to investigate the dietary trophic level of fledgling songbirds

ABSTRACT Use of early successional habitat by mature forest birds during the postfledging period is well documented, but reasons for this habitat shift remain elusive. Although forest‐breeding songbirds are primarily insectivorous during the nestling and early fledgling periods due to high protein requirements, older fledglings may adopt a heavily frugivorous diet. Our objectives were to use stable isotopes to examine the dietary trophic level of juveniles of three species of mature forest songbirds to determine if juvenile songbirds heavily consume fruit resources during the postfledging period and to evaluate a possible link between diet and energetic condition. We collected the outer right rectrix and several body feathers from 34 Wood Thrushes (Hylocichla mustelina), 34 Ovenbirds (Seiurus aurocapilla), and 35 Scarlet Tanagers (Piranga olivacea) captured in regenerating clearcuts in southeastern Ohio in 2005 and 2006. We also collected fruit and arthropod samples from each clearcut. Isotopic values of body feathers were significantly higher (more enriched) than those of rectrices in all cases except values of δ¹³C for Ovenbirds where we found no difference between body and rectrix feathers. These results suggest that juvenile songbirds did not undergo a strong shift to frugivory during the postfledging period, and arthropods were the primary source of protein during the period when rectrix and body feathers were growing. In addition, the energetic condition of birds was not related to the isotopic signature of feathers. Although our results are inconsistent with the hypothesis that juveniles move into regenerating clearcuts enabling them to shift to a primarily frugivorous diet during the postfledging period, they may consume fruit for nonprotein requirements, such as lipids and carbohydrates.     

Possible Fruit Protein Effects on Primate Communities in Madagascar and the Neotropics

Background

The ecological factors contributing to the evolution of tropical vertebrate communities are still poorly understood. Primate communities of the tropical Americas have fewer folivorous but more frugivorous genera than tropical regions of the Old World and especially many more frugivorous genera than Madagascar. Reasons for this phenomenon are largely unexplored. We developed the hypothesis that Neotropical fruits have higher protein concentrations than fruits from Madagascar and that the higher representation of frugivorous genera in the Neotropics is linked to high protein concentrations in fruits. Low fruit protein concentrations in Madagascar would restrict the evolution of frugivores in Malagasy communities.

Methodology/Principal Findings

We reviewed the literature for nitrogen concentrations in fruits from the Neotropics and from Madagascar, and analyzed fruits from an additional six sites in the Neotropics and six sites in Madagascar. Fruits from the Neotropical sites contain significantly more nitrogen than fruits from the Madagascar sites. Nitrogen concentrations in New World fruits are above the concentrations to satisfy nitrogen requirements of primates, while they are at the lower end or below the concentrations to cover primate protein needs in Madagascar.

Conclusions/Significance

Fruits at most sites in the Neotropics contain enough protein to satisfy the protein needs of primates. Thus, selection pressure to develop new adaptations for foods that are difficult to digest (such as leaves) may have been lower in the Neotropics than in Madagascar. The low nitrogen concentrations in fruits from Madagascar may contribute to the almost complete absence of frugivorous primate species on this island.     

Energy supply of the okapi in captivity: fermentation characteristics of feedstuffs

A variety of feeds are used in the nutrition of browsing ruminants. During digestion trials on okapis, feedstuffs of different facilities were sampled and the Hohenheim gas test was used as in vitro fermentation method to quantify their fermentative behavior. Forty‐six feeds were analyzed (7, fruit and vegetable; 11, energy concentrates and pelleted compounds; 13, forage; 9, browse leaf; 6, small and large twig samples). Gas production of these samples was recorded after 2, 4, 6, 8, 10, 12, and 24 hr of fermentation. Browse leaf samples were additionally analyzed with a tannin‐binding agent (polyethylene‐glycol) to assess limiting effects of condensed tannins. Metabolizable energy (ME) was estimated from 24 hr gas production according to standard regressions. Vegetables and particularly fruits were found to yield very high gas productions during the first 2 hr of fermentation, whereas unmolassed beet pulp was found to have a more even distribution of gas production/energy release over total fermentation time. Feeds like rolled oats or bread were evaluated to yield very high energy contents of >14 MJ ME/kg dry matter (DM). Alfalfa (Medicago sativa) hay had a comparable fermentation pattern to fresh browse samples, characterized by a high fermentation rate. In conclusion, energy‐rich constituents for captive ruminant diets should not include larger amounts of vegetables and especially fruits, due to their very fast fermentation during the initial phase of fermentation and the connected risk of rumen acidosis. Energy‐concentrates like beet pulp (unmolassed) showed moderate fermentation characteristics and energy content and are well suited as a component of zoo ruminant diets. Energy‐concentrates with very high energy densities (>13 MJ ME/kg DM) like bread or rolled oats are not suitable for a diet that is intended to promote long feeding times. Various aspects are involved in the decision for appropriate forage for browsing ruminants; based on fermentation pattern, alfalfa hay seems to be a reasonable substitute for browse leaves. Zoo Biol 0:1–16, 2006. © 2006 Wiley‐Liss, Inc.     

Behavioral Ecology of Sympatric Chimpanzees and Gorillas in Bwindi Impenetrable National Park,Uganda: Diet

Via a field study of chimpanzees (Pan troglodytes schweinfurthii) and gorillas (Gorilla gorilla beringei) in Bwindi Impenetrable National Park, Uganda, we found that their diets are seasonally similar, but diverge during lean seasons. Bwindi chimpanzees fed heavily on fruits of Ficus sp., which were largely ignored by the gorillas. Bwindi gorilla diet was overall more folivorous than chimpanzee diet, but was markedly more frugivorous than that of gorillas in the nearby Virunga Volcanoes. During 4 mo of the year Bwindi gorilla diet included more food species than that of the chimpanzees. Three factors in particular—seasonal consumption of fibrous foods by gorillas, interspecific differences in preferred fruit species, and meat consumption by chimpanzees—contributed to dietary divergence between the two species. When feeding on fruits, gorillas ate Myrianthus holstii more frequently than chimpanzees did, while chimpanzees included more figs in their annual diet. Chimpanzee diet included meat of duikers and monkeys; gorilla frequently consumed decaying wood.     

Energy supply of the okapi in captivity: intake and digestion trials

In the nutrition of browsing ruminants in captivity, adequate nutrient digestibility and energy content of diet is debated. Problems related to energy‐provision and low forage intake have been reported for the okapi and other browsers like the giraffe, particularly during winter. High‐fiber concentrates like unmolassed beet pulp have some potential to improve the nutritional management of these species. Using a total of six okapis in captivity, seven feeding trials were carried out at two facilities (A+B) on a structured but opportunistic base. Three trials (A₁, A₂, B₁) were conducted when animals were fed their regular diet including grain based energy concentrates, fruits and vegetables, and alfalfa (Medicago sativa) hay. Two trials (A₅, B₂) examined the effect of unmolassed beet pulp, and two (A₃,₄) examined the effect of unmolassed beet pulp+fresh browse. Daily intake and feces production were quantified over 8–12 days. Samples were analyzed for dry matter, crude ash, neutral detergent fiber (NDF)/acid detergent fiber (ADF)/acid detergent lignin (ADL), crude protein, and gross energy. Metabolizable energy content of diets was estimated via a factor (0.83) from digestible energy. The proportion of beet pulp in diets was 13% (A₃), 24% (A₄), 20% (A₅), and 21% (B₂). Browse proportion was 11% (A₃) and 32% (A₄). Daily feed intake ranged between 1.5–1.7% of body weight (BW), digestibility of organic matter between 61–74%. Digestibility of fiber (NDF) was higher in beet pulp diets (A₃=39%, A₄=60%, A₅=54%, B₂=61%) than in the others (A₁=48%, A₂=33%, B₁=48%). Supply of metabolizable energy (ME) ranged between 0.50–0.70 MJ ME/(kg BW^0.75*day), meeting energy requirements of okapis of 0.50–0.53 MJ ME/(kg BW^0.75*day) in general. Diets with beet pulp+browse were not found to be highest, but in the upper level of the range of forage proportions of this study. Palatable browse species were preferred over all other feedstuff offered. The use of unmolassed beet pulp as energy‐concentrate for browsing ruminants like the okapi can be recommended because diets high in this high‐fibre feedstuff resulted in adequate energy intakes. Zoo Biol 0:1–14, 2006. © 2006 Wiley‐Liss, Inc.