J-M. Hatt

Zurich Zoo and Division of Zoo Animals and Exotic Pets, University of Zurich, Winterthurerstrasse
260, CH – 8057 Zurich.

Digestibility studies have traditionally been performed on live animals. Trials to measure digestibility in vitro have so far not been successful on a larger scale. This is one of the main reasons, why scientific digestibility studies in non-domestic animals and especially in zoo animals still are rare compared to domestic animals. Due to the fact that zoo animals are not tame they are more difficult to handle, controlled feeding and sampling are complicated and may even be dangerous. Since total faecal collection, which is a reliable and commonly used technique in domestic animals, can only rarely be applied in zoo animals alternatives are have been looked for in the past. The increasing need for digestibility studies which are a prerequisite for the understanding of digestive strategies in zoo animals and hence are the basis for the correct feeding, has led to the search for alternatives to performe digestive studies in zoo animals. Inert marker systems have been found to be an important tool for such studies and they have been applied in several zoo animals. Markers may allow to measure digestibility, intake, faecal output, digesta kinetics and even diet composition, without the use of total faecal collection and individual caging. However the uncritical use of markers may also bear the source of important mistakes being made as to the interpretation of results. The present talk aims at presenting the frequently used internal (which are naturally present in feedstuffs) and external (which are mixed into the diet) marker systems used in zoo animal nutrition. Frequently used internal markers are: lignin, HCl-insoluble ash, manganese (Mn2+). External markers are: chromic oxide (Cr2O3), mordants (Cr, Ce ect.), cobalt ethylenediamine tetra-acetic acid (Co-EDTA). A new marker system in zoo animal nutrition, n-alkanes, is presented, which may be used both as internal and external marker. N-Alkanes, which are found in the epicuticular waxes of plants as mixtures of different carbon chain lengths, have received considerable attention in domestic animals in the last 15 years. A major advantage of the n-alkane technique is that it allows the estimation of digestibility and intake with the same marker system and therefore considerably reduces laboratory work. The n-alkanes have also been used as makers to estimate dietary proportions of different plant species or plant components Since different plant species tend to have differing mixtures of odd-chain alkanes (chain lengths in the range, 21 to 35 carbon atoms) diet composition can be estimated from the patterns of alkanes in the faeces and in the dietary components. Similarly, the dietary proportions of different component feedstuffs can be estimated by having them labelled with separate synthetic nalkanes (usually even-chain). Examples are given under which the different markers haven been used and their advantages and disadvantages will be discussed. Common mistakes connected with use of marker systems will be emphasized, such as the recovery of markers in faeces, analytical reliability, contamination and migration.


R. Gisler1*, J-M. Hatt1, R.W. Mayes2, M. Lechner-Doll3, M. Clauss4, A. Liesegang5 and M. Wanner5

1Division of Zoo Animals and Exotic Pets, University of Zurich, 8057 Zurich, Switzerland; 2Macaulay
Land Use Research Institute, Craigiebuckler, Aberdeen AB15 8QH, United Kingdom; 3Institute of Zoo Biology and Wildlife Research, 10315 Berlin, Germany; 4Institute of Animal Physiology,
Physiological Chemistry and Animal Nutrition, Ludwig-Maximilians-Universität, 80539 Munich, Germany; 5Institute of Animal Nutrition, University of Zurich, 8057 Zurich, Switzerland.

Digesta markers are used routinely to calculate faecal output and to estimate digestive kinetics. Marker systems, which have been used in reptiles, include water-insoluble dyes, coloured glass beads and vinyl discs, pieces of plastic tape, fluorescent powder, polyester strips and coloured tissue papers. The kinetic behaviour of both liquid and particulate digesta phases in the gut, has only recently been investigated in reptiles. Cobalt ethylene-diamine tetra-acetic acid (Co-EDTA), ytterbium-marked particles and chromium-mordanted fibre were successfully used in tortoises (Xerobates agassizii). In the insectivorous six-lined racerunner (Cnemidophorus sixlineatus) the kinetics of water-soluble and lipid-soluble phases were studied with [14C]-polyethylene glycol and [3H]-glycerol triether respectively. Most studies that estimated apparent digestibility in reptiles relied on total excreta collection. Chromic oxide (Cr2O3) has been used as an inert marker in green turtles (Chelonia mydas) and in American alligators (Alligator mississipiensis). Natural internal markers have also been used in reptiles: Aciddetergent lignin (ADL) was found to be an acceptable marker in two species of tortoises, and manganese (Mn2+) has been used in a herbivorous lizard (Sauromalus obesus). Most marker systems, have been used in reptiles without thorough validation, which is a disadvantage for the comparison of the results obtained in different studies. A concentration on fewer marker systems would therefore be an important achievement. A marker system that could be of special interest under these circumstances are n-alkanes, carbon chains of different length, which are found in the epicuticular waxes of plants. Alkanes have received considerable attention in the last 15 years, for the study of different aspects of digestive strategies, such as digestibility, diet intake, food selection, and digesta kinetics in mammals, birds and fishes, and to estimate dietary proportions of different plant species or components in the diet of ruminants. A major advantage of the n-alkane technique is that it allows the estimation of different parameters with the same marker system and therefore considerably reduces laboratory work. Two trials were carried out to validate the use of n-alkanes for the first time in a reptile species. Eleven Galapagos giant tortoises (Geochelone nigra) were used for estimating different parameters of their digestive physiology with the alkane method. Trial 1 was a kinetic study with determination of the mean retention time (MRT) in four adult and four juvenile tortoises. Estimates of digesta MRT obtained using n-alkanes were compared with those derived from the use of the respective liquidphase and particulate-phase markers, Co-EDTA and Cr-mordanted fibre. In trial 2, diet composition, food intake and apparent digestibility were determined in two adult and seven juvenile tortoises. The results obtained with the alkane method were compared to values of observation and total faecal collection and to results of two traditional markers acid-insoluble ash (AIA) and acid-detergent lignin (ADL). In conclusion the current study showed clearly that n-alkanes possess a great potential as markers in herbivorous reptiles, since they allow the estimation of different aspects of digestive physiology with one marker type only. The use of the alkane method in future studies will be discussed and examples given in the presentation.


K. Fraser

Animal Conservation and Research Dept., Royal Zoological Society of Scotland, Murrayfield, Edinburgh EH12 6TS, Scotland

Due to a lack of knowledge and alternative feeds, hoofstock in zoos have often been fed commercially available agricultural feeds designed for high production animals. In contrast to the goals of agricultural production, e.g. meat, milk or eggs, a zoo diet aims to provide correct nutrition to minimise the incidence of health problems and improve quality of life. Problems in zoo species associated with agricultural products include excess horn and hoof growth, kidney and liver problems, acidosis, obesity and pathological changes in ruminant guts. In the past, it has been difficult to compare diets with requirements as it involved long, labour intensive calculations. However, with the advent of the Zootrition software program, it is now possible to evaluate nutritional quality of diets and compare with dietary nutrient recommendations from TAG nutrition advisors and sources such as research articles. This paper describes the steps involved in changing hoofstock diets to ones more suitable to exotic species, using an appropriate software program.
Ungulate diet
The animals and feed involved in the study were:
Species Pelleted Diet Costs per Day(£)
camels Cattle Cobs 0.99
Arabian oryx
Scimitar Horned oryx
Red Label dairy pellets 2.73
Western Grey kangaroos
Bennet's wallabies
Diet A pellets 7.68
The diets were entered into the software program and compared with information on the requirements of exotic species. The inappropriateness of the diets became apparent. The agricultural pellets, containing an average protein content of 20%, were unsuitable for exotic species, which require Ca. 8 - 10% protein. The fibre levels in the agricultural pellets were on average 6%, whereas the requirements of exotic species can be up to 30% fibre.
Trial period for diet change
A new pellet designed for exotic ungulate species, 'Wildlife Nut', containing 8% protein and 25% fibre, as well as all the vitamins and minerals at appropriate levels was tested on the ungulates. A trial was carried out, which involved substituting small amounts of the old diet for the new pellet over 14 days, and monitoring consumption and health codes for body, coat and faeces condition.
Monitoring - health codes database
Keepers monitored animals and coded for health condition and pellet consumption daily. This ensured that if any animal were to suffer any ill effects due to the change of diet, it would be noticed quickly. The codes were entered into a database, which allowed easy analysis of the condition of the animals over the trial period. The new pellet was a success as the animals consumed them readily. Health codes over the period showed that there were no apparent adverse effects. The diet was then fully introduced and the animals continued to be coded weekly for faeces, body and coat condition, to monitor long term effects.
With many zoos being under a strict budget, the cost of animal feed is important. The cost of the diets before and after were compared using the software and the results showed that the new diet cost £6.49 in comparison with the old at £11.40 per day. A careful look using new software at existing diets can not only provide a healthier diet, but potentially cut costs also.


A.K. Bond

Bristol Zoo Gardens, Clifton, Bristol, BS8 3HA, UK and Cardiff University, The Department of
Biosciences, Park Place, Cardiff.

The purpose of an ongoing study at Bristol Zoo Gardens is to establish the nutritional content of the diets that are consumed by various species in the Zoo. Zootrition is a software package that can analyse diets if their constituents are known. If software such as Zootrition is to be of value to the Zoo community the data entered into it must be accurate. This paper outlines some of the many areas where inaccuracies occur, and suggests ways in which these problems can be reduced. Food items are not widely referred to by their scientific names, which leads to confusion when searching the literature for nutritional analysis data and when using the Zootrition software. Once identified, the acquisition of accurate and detailed nutrient analysis for food items also presented a challenge, even for manufactured feeds. Of those contacted 75% of the suppliers of manufactured foodstuffs could not, or would not for commercial reasons, provide a detailed nutrient analysis of their product. The diets offered and proportions consumed by 16 species have been recorded (6 birds, 10 mammals) and entered into the Zootrition software. Whilst the diet sheets kept on section are a useful reference, they are not a definitive guide for the following reasons:
· Food items are not listed as weights but arbitrary amounts e.g. two apples.
· Food items considered as enrichment tools are frequently overlooked.
· It was found that actual diets were determined predominantly by the keepers’ interpretation of the diet sheets, and much variation occurred between keepers.
· All diets studied contained fresh foodstuffs and in all cases this component of the diet was subject to great variation, not only due to availability (both daily and seasonally) but also because variation is perceived as a form of enrichment. Data collection techniques have been revised on several occasions and have largely been determined by the feeding behaviour of the species being studied. Ascertaining what is actually eaten is important:
· Many animals do not consume the entire food item – leaving peel, seed hulls etc. Therefore merely weighing remaining food items may give misleading results. For instance, because the nutritional content of orange peel and orange flesh are different, merely measuring what remains and analysing as ‘orange’ will not give accurate results.
· Food may be eaten by wild rodents and birds.
· The European Hamster creates food stores that, the study found, were not necessarily eaten at a later date.
· Animals fed on a mixed diet may feed selectively as this study noted in Toucan (Toco toucana) Hornbill (Penelopides sp) and Cockatoo (Cacatua sp). In this case it is necessary to identify the proportions of each component consumed. However, presenting these components separately affected feeding behaviour. One method that was adopted was to dry out the uneaten food to enable the components to be separated sufficiently. The study of some diets presents more practical difficulties than others. Serious consideration must be given to such problems that, if not addressed, will lead to inaccurate data collection.


P. Wolf*, S. Graubohm and J. Kamphues

Institute of Animal Nutrition, Hanover School of Veterinary Medicine, Bischofsholer Damm 15, D-30173 Hannover.

Since a few years feeding of pelleted/extruded diets to parrots is discussed controversially. Some bird fanciers dislike the use of these diets and put forward body weight losses of their parrots during conversion from usual seed mixtures to formulated diets. Furthermore a reduced time for feed intake is stated, that is linked with behaviour disorders (feather biting/picking due to boredom) and a reduced attrition of the beak. In spite of those reservations pelleted/extruded diets allow the composition of a well-balanced diet, that meets the requirement of the parrot in each stage of life. Furthermore a pelleted or extruded diet prevents the selection of individual ingredients within the offered feed (a.e. the choice of seeds like sunflower seeds, that are characterized by a high fat as well as energy content with the risk to obesity). Another aspect is the improved hygienic quality due to the common used ingredients (mostly based on cereals). In feeding trials with amazons, grey parrots and cockatoos the parameters mentioned above were proofed. A comparison of the chemical composition shows great differences between formulated diets and commercial seed mixtures based on fatty seeds like sunflower seeds, safflower, hemp, pumkins, peanuts a.s.o. (see table 1). Compared to seed mixtures the pelleted/extruded diets are characterized by lower crude protein, crude fat, crude fiber and energy contents, but higher amounts of carbohydrates (formulated diets are based on maize, wheat and oat especially). In particular the calcium content of 10.9 g/kg dry matter in average indicates a high calcium supply. The calcium:phosphorus-ratio was well balanced. The sodium contents point to a supply, even if amounts of 1-2 g sodium per kg dry matter are not recommended.

Table 1: Chemical composition of pelleted/extruded diets compared to seed mixtures data per kg dry matter pelleted/extruded diets (n=16) seed mixtures (n=10)*
crude protein (g) 196 ± 38.7 243 ± 63.6
crude fat (g) 81.6 ± 24.9 383 ± 125
crude fiber (g) 32.0 ± 14.0 38.2 ± 25.1
carbohydrates (g) 566 ± 56.4 284 ± 30.9
energy (MJ ME) 15.8 ± 0.60 21.4 ± 3.51
calcium (g) 10.9 ± 4.10 1.79 ± 1.24
phosphorus (g) 5.68 ± 1.26 9.08 ± 3.59
sodium (g) 3.21 ± 1.90 0.54 ± 0.24
*related to the ‘kernels’, that means the real intake after dehusking/shelling of the seeds

Conversion of parrots from usual seed mixtures to unknown formulated diets was done within a short time and without any problems (a.e. refusal of the diet combined with body weight losses). Offering seed mixtures ad libitum a typical rhythm of feed intake could be observed (higher ingesting activities in the early morning and in the afternoon), whereas formulated diets were ingested continuously during the whole day. The time spent for feed intake (measured in minutes per gram feed) did not differ significantly between pelleted/extruded diets and seed mixtures. When formulated diets were fed digestibility of organic matter varied between 76 and 84% (in comparison: Æ 78% ingesting fatty seeds and Æ 87% fed seeds rich in carbohydrates). In general the results do not underline the reservations against formulated diets, but for a final
estimation long time studies (a.e. of several years) are absolutely necessary.