Landscape-scale feeding patterns of African elephant inferred from carbon isotope analysis of feces

The African elephant (Loxodonta africana) is a large-bodied, generalist herbivore that eats both browse and grass. The proportions of browse and grass consumed are largely expected to reflect the relative availability of these resources. We investigated variations in browse (C(3) biomass) and grass (C(4)) intake of the African elephant across seasons and habitats by stable carbon isotope analysis of elephant feces collected from Kruger National Park, South Africa. The results reflect a shift in diet from higher C(4) grass intake during wet season months to more C(3) browse-dominated diets in the dry season. Seasonal trends were correlated with changes in rainfall and with nitrogen (%N) content of available grasses, supporting predictions that grass is favored when its availability and nutritional value increase. However, switches to dry season browsing were significantly smaller in woodland and grassland habitats where tree communities are dominated by mopane (Colophospermum mopane), suggesting that grasses were favored here even in the dry season. Regional differences in diet did not reflect differences in grass biomass, tree density, or canopy cover. There was a consistent relationship between %C(4) intake and tree species diversity, implying that extensive browsing is avoided in habitats characterized by low tree species diversity and strong dominance patterns, i.e., mopane-dominated habitats. Although mopane is known to be a preferred species, maintaining dietary diversity appears to be a constraint to elephants, which they can overcome by supplementing their diets with less abundant resources (dry season grass). Such variations in feeding behavior likely influence the degree of impact on plant communities and can therefore provide key information for managing elephants over large, spatially diverse, areas.     

Feed intake and dietary composition of iron (Fe), copper (Cu), vitamin E,and tannic acid of five captive black rhinoceros (Diceros bicornis) in a UK collection

The black rhinoceros (Diceros bicornis) is a critically endangered species facing multiple anthropogenic pressures in its natural home range across Africa. Black rhinoceros are difficult to maintain ex situ and subject to diseases that are linked with captive dietary factors. Hemochromatosis is of particular concern, as it is a common finding at necropsy of captive adults, and has been linked to excessive dietary iron intake. This intake study investigates the select nutrient composition of the diets offered to and consumed by five captive black rhinoceros in a UK zoo to evaluate, ensure adequacy, and/or make adjustments if necessary. Alfalfa hay, pellets and six browse species offered were analyzed for iron (Fe), copper (Cu), vitamin E, and tannic acid content. Intakes were quantified and evaluated against levels found in wild diets and the currently available feeding guidelines for black rhinoceros. Diets eaten by five individual rhinoceros (1.4%–2.3% of bodyweight dry matter [DM] intake), comprising 68%–82% hay, 6%–13% pellets, and 13%–27% browse, contained 76–98 mg/kg Fe (on a DM basis), fell within the ranges of plants eaten by free‐ranging rhinoceros (45–140 mg/kg DM), as well as values recommended for captive‐fed browsing rhinoceros (50–100 mg/kg DM). Consumed diets were found to be marginal to adequate in Cu (9–11 mg/kg DM) compared with the recommended 10 mg/kg DM; dietary vitamin E ranged from 54 to 79 IU/kg DM, and tannic acid measured 13–14 g/kg DM. Commercial pellets were the primary contributor of dietary Fe, Cu, and vitamin E, containing up to 10 times more of each of those nutrients than the forages. Native browses were important sources of lower Fe ingredients, as well as appropriate levels of dietary Cu and vitamin E (dependent on species). Interestingly, pellets (23 g/kg) and alfalfa hay (14 g/kg) contained higher concentrations of tannic acid compared with any of the browses fed (4–13 g/kg). All nutritional parameters evaluated were close to recommended dietary levels, diets resembled values consumed in the wild, and the animals remained clinically healthy throughout the study. Overall, diets were considered nutritionally adequate for captive feeding of black rhinoceros; evaluating the nutrient composition of all ingredients, including browse plants in diets, provides important information for achieving optimal nutrient balance.     

Diet composition,food intake,body condition,and fecal consistency in captive tapirs (Tapirus spp.) in UK collections

Intake measurements were carried out in 22 tapirs from seven UK zoological collections. Dry matter intake (DMI) ranged from 48 to 86 g/kg^0.75/d. Across collections, the highest proportion of the ingested diet consisted of pelleted feeds (including grains and bread) at 46±17% DMI, followed by commercial produce at 26±12% DMI, roughage (excluding browse) at 17±11% DMI, and browse at 11±11% DMI. The proportion of roughage, crude protein, crude fiber, and neutral detergent fiber levels in the diets investigated were well below levels recommended for domestic horses and other ungulates. Intakes of digestible energy (DE) as estimated from food nutrients using of a standard equation for domestic horses ranged from 0.58 to 0.88 MJ/DE/kg^0.75/d, with many individuals exceeding the assumed maintenance requirement of 0.6 MJ/DE/kg^0.75/d for hindgut fermenters. At values exceeding this DE intake, animals had higher than ideal body condition scores (BCS). Animals with higher BCS (i.e. more obese animals) generally had higher fecal scores (FS) (i.e. softer feces), and both BCS and FS were positively correlated to DMI and calculated DE intake. This suggests that the population studied was generally overfed, with resulting obesity and softer fecal consistency. The use of highly digestible feeds such as commercial produce and pelleted feeds should be restricted in the diets of these animals and roughage intake promoted in order to attempt to achieve normal BCS and FS in this captive population. Zoo Biol 28:279–291, 2009. © 2009 Wiley-Liss, Inc.     

Effect of metabolic acidosis on white-tailed deer antler development

Metabolic acidosis can result when herbivores consume browse diets high in plant secondary compounds. One mechanism for buffering excess acid is the mobilization of calcium and other alkaline salts from the skeletal system. White-tailed deer (Odocoileus virginianus) and other cervids consuming browse during antler formation may use minerals essential for antler development as buffers, resulting in altered antler characteristics. Our research objectives were to examine the effects of metabolic acidosis on mineral metabolism, acid-base homeostasis, and antler development in white-tailed deer. Fifteen male white-tailed deer were assigned to one of three diets: 2% NH(4)Cl, 3% commercial tannic acid, or a basal ration without additive. Two feeding trials were completed on each deer to determine nutrient use. Urine pH and the percentage of urinary nitrogen excreted as NH+4 varied by diet. No significant diet or trial effects occurred for nitrogen, calcium, phosphorus, magnesium, or sodium use. Urinary calcium excretion varied between diets. No dietary differences were observed for antler characteristics. The NH(4)Cl diet induced metabolic acidosis but did not alter antler development in white-tailed deer. Skeletal mineral reserves and mineral intake appeared sufficient to buffer excess acids and support antler development.     

Feed intake,diet utilization,and composition of browses consumed by the Sumatran rhino (Dicerorhinus sumatrensis) in a North American zoo

The Sumatran rhino (Dicerorhinus sumatrensis), presently indigenous to the Malay peninsula and the islands of Sumatra and Borneo, is faced with extinction. It is estimated that fewer than 400 individuals still exist in the wild. In response, concerted efforts have been made to maintain and breed this species in captivity, and proper diet and nutrition underlie reproduction. The present feeding trial characterizes a diet fed to three Sumatran rhinos at the Cincinnati Zoo and Botanical Garden. The diet consists of mixed alfalfa/orchard grass hay, a variety of browses, grain pellets, produce (apples and bananas), and a vitamin E supplement. All three rhinos maintained body weight (614–761 kg), regular patterns of bowel movements, and fecal consistency and composition throughout the three 5‐day trials. Dry matter intake (DMI) ranged from 1.40 to 2.49% of body mass. Browse contributed by far the majority of nutrients to the diets in this study, from 62 to 83% of DMI. The nutrient composition of six species of subtropically grown browses (two from differing locations, for a total of eight browses characterized) showed that leaves did not differ from twigs in water or lignin content, but leaves contained higher concentrations of protein (both crude and bound) and ash, as well as lower fiber fractions. Of the macrominerals analyzed, only phosphorus differed between leaves and twigs, with twigs containing significantly more. No differences were seen between leaves and twigs in iron, molybdenum, or zinc content, but leaves contained lower concentrations of copper and higher concentrations of manganese and selenium compared with twigs from the same plants. Dry matter digestibility averaged approximately 50%. The only overt imbalances detected when comparing rhino diets with nutrient recommendations for domestic equids were excess calcium relative to phosphorus intake and low copper intake. These data, combined with information on native browse composition, intake, and digestibility, should greatly assist in providing suitable diets for this highly endangered species. Zoo Biol 19:169–180, 2000. © 2000 Wiley‐Liss, Inc.     

Diet and distribution of elephant in the Maputo Elephant Reserve, Mozambique

The distribution and diet of the elephants of the Maputo Elephant Reserve were studied using dung counts, satellite tracking and faecal analysis. The results were compared with earlier data from before the civil war in Mozambique. The elephant population decreased during the civil war, but 180 animals still remain. Earlier studies described the elephants as preferring the grass plains. Currently, the elephants prefer the dense forest patches over the high quality forage found in the grass plains. Water salinity affected distribution; elephant dung piles were found closer to fresh water in the dry season. A total of 95 different plant species were identified in the faeces. The percentage of grass was relatively low compared with other studies, increasing at the beginning of the rainy season. At the end of the dry season, elephants concentrated on the few available browse species with young leaves, but generally preferred grass species to browse species. Diet composition was mainly affected by season and less by habitat. The elephants have changed their habitat preference in reaction to poaching, and probably increased the contribution of browse species in the diet. The presence of forest patches has been vital for the survival of the elephants.     

Evaluation of a pelleted diet in a colony of marmosets and tamarins

By offering various pelleted diet modifications to five species of Callitrichidae, a palatable 24% protein diet was developed. The animals received limited fruit supplement, and families received an additional meal of commercial baby food. The pellets supplied approximately 75% of dietary energy and 95% of total protein. In 15 months on this regimen, mortality dropped drastically and fertility improved. No signs of a nutritional deficiency were observed. It was concluded that the nutrient levels of this diet were adequate or above actual requirements.     

Palatability and digestibility of soya- and milk proteins in Callithricidae

4 protein sources were tested for palatability, digestibility, influence on bodyweight and consistency of faeces in Callithrix jacchus and Saguinus fuscicollis. The protein sources were incorporated at crude protein levels of 12, 17 and 22% in a pelleted diet. A banana supplement was also fed which reduced the total protein content to 10.7, 14.7 and 18.3%. The test diets, fed for 3 weeks, were well accepted with the milk proteins being slightly preferred. Consumption of the 12% protein pellets was greater than their 22% equivalents. True protein digestibility was calculated to be 97% for lactalbumin, 96% for casein, 90% for soy protein concentrate and 83% for soyabean meal. Changes in bodyweight were negligible. Dry matter of faeces varied between 25% (lactalbumin diets) and 28% (casein diets), but did not change with increasing protein intake. Increasing levels of cellulose, from 2.4 to 7.2% total crude fibre lowered the apparent protein digestibility from 84.3 to 79.2% and the digestibility of dry matter from 82.2 to 76.5%.     

Sex and size related differences in the dry season feeding patterns of elephants in Chobe National Park, Botswana

Differences in feeding patterns of the African elephant were examined by sex and age during the dry season in a dystrophic savanna-woodland ecosystem in northern Botswana. Adult males had the least diverse diet in terms of woody plant species, but they consumed more plant parts than family units. The diameter of stems of food plants broken or bitten off was also greater for adult males than for females and subadult males. Adult males spent more time foraging on each woody plant than did females. The number of woody plant species and individuals present were higher at feeding sites of family units than at feeding sites of adult males, indicating that family units positioned themselves at feeding sites with higher species diversity than those of males. We argue that the most likely explanation for these differences is related to the pronounced sexual size dimorphism exhibited by elephants, resulting in sex differences in browsing patterns due to the allometric relationships that govern the tolerance of herbivores for variation in diet quality. From our results this Body Size Hypothesis is accepted rather than the alternative Scramble Competition Hypothesis, which predicts that adult male elephants consume lower quality browse because they are displaced from preferred browse as an outcome of scramble competition with adult females and their offspring. If the feeding patterns of adult male elephants were affected by intersexual scramble competition, we would expect adult males to browse at a higher level in the canopy than the smaller-bodied females and their offspring. No evidence was found for this, although adult females were found to browse at a higher level in the canopy when feeding in close proximity to subadults and juveniles than when feeding alone. Sex differences in elephant browsing patterns are, we propose, of relevance to understanding and managing elephant impacts on African woodlands.     

Food Sorting by Collared Lemmings (Dicrostonyx groenlandicus) and Prairie Voles (Microtus ochrogaster): A Cautionary Note for Digestibility Studies

Small herbivores are often confronted with poor quality diets; in response to this situation, they may sort their food to increase diet quality. Neutral detergent fiber (NDF) levels were measured in three pelleted diets fed to collared lemmings (Dicrostonyx groenlandicus) and prairie voles (Microtus ochrogaster) and compared to levels in orts collected from the same diets and animals. Lemmings sorted and discarded the fibrous parts of food pellets on all three diets (17.3% to 25.9% higher NDF in orts), whereas voles sorted out fibrous particles on only one diet. Calculations of NDF digestibility were significantly reduced by particle sorting (up to 16.9% decrease in digestibility). In reviewing the literature, we found that in more than half of studies examined, orts may not have been analyzed for these differences. Researchers must carefully consider such effects, especially when conducting digestibility studies with herbivores on pelleted diets.     

Nutrition of captive lowland anoa (Bubalus depressicornis): a study on ingesta passage,intake, digestibility,and a diet survey

Members of the Bovini genus are classified as grazers. Smaller species of ruminants are not expected to be able to digest particularly fibrous diets and are more often classified as intermediate feeders or browsers. Anoas (Bubalus spp.) are interesting in this respect as they are the smallest representatives of the Bovini, being only 10–20% of the body weight of other species of the same genus. A feeding trial was carried out with four lowland anoas (Bubalus depressicornis) at London Zoo, investigating diet digestibility by total fecal collection and passage rates by the simultaneous administration of a fluid (Co‐EDTA) and a particle (Cr‐mordanted fibre <2 mm) marker. The diet consisted of legume hay, dairy cow pellets, browse, fruits, and vegetables. The achieved digestibility coefficients averaged 70±4% for dry matter and 57±7% for cell walls (NDF). Mean retention times for the total gastrointestinal tract were 25±4.1 hr for fluid and 39±6.7 hr for particles, respectively. The ratio of forestomach particle:fluid retention was 2.14±0.40. Additional information regarding anoa diets in captivity was collected through a survey targeting all institutions that have anoas in their collection currently. Suitability of the provided diet was evaluated using the ratio of unstructured:structured feeds (unstructured feeds pellets, grains, produce; structured feeds=roughage, browse) on a dry matter basis and an assumed complete consumption of offered unstructured diet items, with only the remaining intake capacity being met by structured items. The use of this ratio reliably predicted one facility that reported chronic diet‐related problems. As other ruminants, anoas should receive a diet with restricted amounts of concentrates and fruits. The comparatively high fibre digestibility and the high selective particle retention in the forestomach suggest a classification of an intermediate/grazing ruminant. Zoo Biol 24:125–134, 2005. © 2005 Wiley‐Liss, Inc.     

Circulating nutrients and hematological parameters in managed African elephants (Loxodonta Africana) over a 1-year period

African elephants (Loxodonta Africana) are currently considered a vulnerable species. One key to improving methods of species management is to better monitor and understand elephant nutrition. Analyzing circulating nutrients is one of the best and least invasive methods of monitoring managed elephant nutrition, but limited reference values are available. This study examined the circulating basic hematology concentrations, minerals, vitamins A, D, and E, and fatty acids of six African elephants (two males and four females) at the North Carolina Zoo collected monthly from March 2016 to April 2017 and compared levels among seasons. Creatinine (CRE) and albumin had seasonal differences (p ≤ .05). Calcium, magnesium, phosphorus, potassium, selenium, zinc, cobalt, manganese, and molybdenum displayed seasonal differences (p ≤ .05). Retinol and 25-hydroxyvitamin D₂ had seasonal differences (p ≤ .05). Linoleic acid, α-linolenic acid, arachidonic acid, total omega-3 fatty acids, total omega-6 fatty acids, and the omega-6 to omega-3 ratio showed seasonal differences (p ≤ .05). Findings suggest that exogenous vitamin E supplements may not be necessary with a mixed feedstuff diet (hay, fortified concentrate pellet, browse, and produce) based on circulating values. This data offer updated information on circulating reference values and novel circulating concentrations of nutrients for Southeastern US managed African elephants that can be used to inform nutritional and health management in all similar habitats.     

Influence of two different diets on fluid and particle retention time Javan langur (Trachypithecus auratus auratus)

In captivity, langurs (foregut fermenting primates) often suffer from digestive disorders, and in particular display soft stools on diets with a high proportion of fruits, vegetables, and grain products. In this study, we tested whether the improvement in feces consistency expected after an omission of vegetables from a conventional diet was also accompanied by a change in the excretion pattern as measured by the mean retention time (MRT). Two adult Javan langurs were kept together and offered a conventional diet of pellets, browse, vegetables, or a diet consisting of pellets and browse only. MRT were measured with cobalt-EDTA as the fluid and chromium oxide as the particle marker before, during, and after the test diet, collecting the feces of both animals together. MRTs of fluids and particles were longer (47/49 h) on the test diet as compared to the usual diet (42/43 h). Feces consistency improved during the test period. The test period was marked by an increased fiber intake; however, on the conventional diet, dietary water intake exceeded the calculated water flux for these animals distinctively, due to the high proportion of vegetables. Therefore, it cannot be decided whether the increase of fiber level alone or also a reduction of the excessive water intake was responsible for the changes observed. Comparing the results of this study to other studies on ingesta retention in foregut fermenting primates, no correlation between the body mass of the animals and the MRTs measured is evident, which is in accordance with observations in other groups of foregut fermenters.     

Reducing saturated fat intake lowers LDL-C but increases Lp(a) levels in African Americans: the GET-READI feeding trial

Reducing dietary saturated fatty acids (SFA) intake results in a clinically significant lowering of low-density lipoprotein cholesterol (LDL-C) across ethnicities. In contrast, dietary SFA’s role in modulating emerging cardiovascular risk factors in different ethnicities remains poorly understood. Elevated levels of lipoprotein(a) [Lp(a)], an independent cardiovascular risk factor, disproportionally affect individuals of African descent. Here, we assessed the responses in Lp(a) levels to dietary SFA reduction in 166 African Americans enrolled in GET-READI (The Gene-Environment Trial on Response in African Americans to Dietary Intervention), a randomized controlled feeding trial. Participants were fed two diets in random order for 5 weeks each: 1) an average American diet (AAD) (37% total fat: 16% SFA), and 2) a diet similar to the Dietary Approaches to Stop Hypertension (DASH) diet (25% total fat: 6% SFA). The participants’ mean age was 35 years, 70% were women, the mean BMI was 28 kg/m², and the mean LDL-C was 116 mg/dl. Compared to the AAD diet, LDL-C was reduced by the DASH-type diet (mean change: −12 mg/dl) as were total cholesterol (−16 mg/dl), HDL-C (−5 mg/dl), apoA-1 (−9 mg/dl) and apoB-100 (−5 mg/dl) (all P < 0.0001). In contrast, Lp(a) levels increased following the DASH-type diet compared with AAD (median: 58 vs. 44 mg/dl, P < 0.0001). In conclusion, in a large cohort of African Americans, reductions in SFA intake significantly increased Lp(a) levels while reducing LDL-C. Future studies are warranted to elucidate the mechanism(s) underlying the SFA reduction-induced increase in Lp(a) levels and its role in cardiovascular risk across populations.     

A food pelleter for experimental diets for rats

Food pellets for an experimental diet for laboratory rats were produced for long-term nephrotoxicity study using a modified, commercially available pasta machine. This method eliminated the disadvantages of powdered diets and provided the advantages of pelleted diets at low production cost. A commercially available, pelleted diet was pulverized, the test agent and water added, and the mixture repelletized. No special feeding equipment was required because the repelletized diet was fed in standard lid-type feeders. It was not necessary to sterilize the diet.     

The effects of cereal particle size and pelleting on the nutritive value of oat-based diets for the growing pig

Oat grains from a single source were ground in a hammer mill, either with no screen present (coarse) or through 1.56 or 4.68-mm screens, to produce three samples with different particle size distributions. At inclusion levels of 850 g kg^?1 the three samples were used as the bases of three otherwise identical diets. Half of each diet was steam pelleted to give pellets of 7-mm diameter and the other half retained as a meal form. Factorially designed metabolism experiments using 30 pigs of 20 kg initial live weight and a growth experiment using 72 individually fed pigs of 25 kg initial live weight were made.Pelleting or particle size of the diet had no significant effect on (a) apparent digestibility of dry matter (DM), modified acid detergent fibre and gross energy (b) digestible (DE) and metabolisable energy (ME) contents (the DE contents of the meal and pelleted diets were 12.81 and 13.03 MJ kg^?1 DM, respectively) and (c) nitrogen retention. Apparent digestibility of the ether-extractable fraction was significantly poorer in meals (cf. pellets) and in the diets based on coarse grains compared with those based on the two finer-ground samples. Also, apparent digestibility of nitrogen was significantly poorer in the diets based on the coarse grains (0.803) compared with that based on the 1.56-mm ground grain (0.832). Growth and efficiency of feed conversion were significantly improved by pelleting the coarse grain diet, and the meal diet based on the coarse grain gave significantly inferior results compared with those from the two other meal diets.     

The Nutritional Balancing Act of a Large Herbivore: An Experiment with Captive Moose (Alces alces L)

The nutrient balancing hypothesis proposes that, when sufficient food is available, the primary goal of animal diet selection is to obtain a nutritionally balanced diet. This hypothesis can be tested using the Geometric Framework for nutrition (GF). The GF enables researchers to study patterns of nutrient intake (e.g. macronutrients; protein, carbohydrates, fat), interactions between the different nutrients, and how an animal resolves the potential conflict between over-eating one or more nutrients and under-eating others during periods of dietary imbalance. Using the moose (Alces alces L.), a model species in the development of herbivore foraging theory, we conducted a feeding experiment guided by the GF, combining continuous observations of six captive moose with analysis of the macronutritional composition of foods. We identified the moose’s self-selected macronutrient target by allowing them to compose a diet by mixing two nutritionally complementary pellet types plus limited access to Salix browse. Such periods of free choice were intermixed with periods when they were restricted to one of the two pellet types plus Salix browse. Our observations of food intake by moose given free choice lend support to the nutrient balancing hypothesis, as the moose combined the foods in specific proportions that provided a particular ratio and amount of macronutrients. When restricted to either of two diets comprising a single pellet type, the moose i) maintained a relatively stable intake of non-protein energy while allowing protein intakes to vary with food composition, and ii) increased their intake of the food item that most closely resembled the self-selected macronutrient intake from the free choice periods, namely Salix browse. We place our results in the context of the nutritional strategy of the moose, ruminant physiology and the categorization of food quality.     

A preliminary study of the behavioral effects of feeding enrichment on African elephants

Although commonly practiced with many species, feeding enrichment in elephants is understudied. The behavioral effects of feeding enrichment were tested in three African elephants by substituting an equal dry weight of browse for hay in an ABA design. The results showed a significant increase in feeding and significant decreases in drinking and inactivity when the browse was present. Additionally, changes in feeding, inactivity, and time spent in contact were observed outside the time the browse was actually presented, although the relationship of these changes to the experimental methodology is unknown. A significant increase in visibility to zoo visitors during the browse conditions demonstrates that browse is an effective, naturalistic method for increasing visibility as well as species-typical behaviors. Managers of captive elephants should consult with a nutritionist to address issues of energetics, nutritional content, and secondary compounds when using browse as feeding enrichment. Zoo Biol 19:485-493, 2000. Copyright 2000 Wiley-Liss, Inc.     

Comparison of diets fed to southeast Asian colobines in North American and European zoos,with emphasis on temperate browse composition

In May and June 1994 a survey of diets fed to captive southeast Asian colobines in European (n = 12) and North American (n = 9) zoos was conducted. Most diets were very complex, comprising an average of 25 ingredients; 149 different foods were listed in responses. Comparison of diets fed showed that European zoos feed a greater variety of fruits and vegetables, and fewer browse plants, than North American zoos. No standardized diet recommendations, based on ingredient or nutrient composition, are currently available for colobines in captivity. Foods eaten by these primates in nature appear to contain higher amounts of fiber and lower protein and soluble carbohydrates than current zoo diets. Temperate browse plants (n = 11 spp.; leaves plus twigs) sampled in New York in summer and autumn contained higher fiber and lower protein levels than diets fed in this survey, and may approximate the nutrient content of food items selected by free-ranging colobines. Fast-growing roses grown in greenhouses, fed primarily in Europe, contained substantially less fiber and higher protein concentrations than other browses offered, and may not be an appropriate substitute for native foods. © 1996 Wiley-Liss, Inc.