The Giraffe inside out


This report is the result of our final research project of the course Animal management of the Van Hall Institute in Leeuwarden. The report is the result of five months filled with hard work during the period April – August 2004.

The project being undertaken during this period was part of the specialization Nutrition and Care of Animals (NC, Voeding en verzorging); ‘testing a recently developed browser concentrate (Browser pellet), by using different techniques’. The project objective is two fold. First, to test a recently developed concentrate. Second, to get more insight in stratification in a browsing species. We have used two techniques at the same time (lignin marker technique, observing to be able to collect faeces of individual animals from a captive group). This was necessary because some of the giraffes involved in this research were kept as a group.

We have experienced this final project as a very learning full period as the execution of this project entails different skills. It required enthusiasm to bring the challenge to a good end, but also, the research was attended with some reverses as well, where self-discipline and perseverance turned out to be indispensable.

This period was also on a personal scale a very positive experience and we would like to thank a few people. At first, we would like to thank Tjalling Huisman for his help and support during these months. We would like to thank Walter Jansen for his help and for making this project possible. Also, we would like to say thanks to our other supervisor at the Van Hall Institute, Dick Kuiper and to Jan van der Kuilen, for their help on the laboratory, to Henri Kuipers for his time to put us wise on the statistical level, and to Lutien Groeneveld for her help and information during the project. We would also like to thank Bastiaan Baan, Liesbeth Mulder and Femke Velthuis for their assistance with the laboratory analysis.
Finally, of course, we would like to thank Marcel Breeschoten and Marc Damen for offering us the opportunity to undertake our research at Artis Zoo and Burgers’ Zoo, and thanks go to the zookeepers for their assistance and their interest shown.

Leeuwarden, August 2004

Mariska van den Berg,
Esther van de Hoek


Browsers and grazers have different nutritional requirements, which are related to the differences between browse and grass. Relatively a lot of problems occur among captive browsers, such as affections of the digestive tract and peracute mortality syndrome (sudden death) (Fowler, 1993; Clauss et al., 2001; Clauss et al., 2003a;). These problems are partly related to the diet offered.
Changes in the digestive tract occur due to an unnatural diet. Zoo nutrition highly reduces selectivity and changes the physiological (or metabolically induced) foraging frequency/feeding rhythm. There is also a lack of stimuli to trigger the sequence/cascade of physiological, biochemical and morphological responses (Hofmann, 2000).
The ingredients of a browser diet are still more based on the diet of grazers, which contain grass components. With this knowledge in mind, a new concentrate was produced by the European Zoo Nutrition Centre (EZNC) and Arie Blok Diervoeding, called Hope Farms “Browser pellet”. One of the high-fiber components of this concentrate is Boskos (concentrate consisting of Acacia and other plants from South Africa) instead of grass components.

This research attempts to test the digestibility of Hope Farms’ Browser pellet compared to other concentrates for browsers, in order to get more insight in the suitability of this Browser pellet in giraffe diets. In this research we have used the giraffe as a model for browsers. Therefore an ABA withdrawal design was used: the baseline condition (A) in which the original concentrates were fed, and the experimental condition (B) in which Hope Farms’ Browser pellet was fed as the substitute for the original concentrate(s) that were fed. Fifteen giraffes (Giraffa camelopardalis) were used in this study, kept in Artis Zoo in Amsterdam and Burgers’ Zoo in Arnhem. These giraffes formed seven research objects (five individual animals and two groups of two and eight animals).
To test the digestibility of Hope Farms’ Browser pellet, compared to the original concentrate(s), the following methods were used:
  • The food intake was calculated, by measuring the intake per research subject of every period;

  • The faeces were collected three times per period, by observing individually in the outside enclosure in Artis Zoo, and taking faeces samples in the inside enclosure in Burgers’ Zoo;

  • ADL indicator method was used for determining total faecal output;

  • Laboratory analyses were performed, to calculate the mean nutrient intake

With these values the digestibility of the different periods could be calculated. With
SPSS 9.0. Repeated Measures ANOVA, Within-Subjects and Between-Subjects tests were performed on the digestibility of the components Gross Energy (GE), Dry Matter (DM), Crude Protein (CP), Crude Fiber (CF), Neutral Detergent Fiber (NDF) and Acid Detergent Fiber (ADF).

The digestibility of a food is closely related to its chemical composition. The fiber fraction of a food has the greatest influence on its digestibility, and both the amount and chemical composition of the fibre are important (McDonald, et al., 1995). The amount of food fed to the giraffes was kept as stable as possible, but some differences occurred. However, this had not the expected effect on the digestibility. The chemical composition of the fibre was different in the three different periods. With all research subjects, CF intake was higher in the B period, but seemed to have no depressing effect on the digestibility of the dietary components CP and Ash. There was no large difference in NDF and ADF intake between the three periods.

In both zoos, the digestibility of crude protein and ash were significantly higher when Hope Farms’ Browser pellet was fed, compared to the original concentrates. The components Gross Energy, dry matter, crude fiber, neutral detergent fiber and acid detergent fiber had no significant difference in digestibility when the Browser pellet, respectively the original concentrate(s) was/were fed.

When looking at the digestibility, the intake and the faeces quality of the ration with the Browser pellet, it can be concluded that the Browser pellet is better suited for giraffes than the original concentrates.


In the past attempts were made to explain the variation in feeding strategies among ruminants in the wild. Individual species where classified as ‘browsers’ or ‘grazers’, based on the types of forage they consumed.
In 1972, Hofmann and Stewart demonstrated that feeding strategies of ruminants could not be classified into two categories and proposed three categories, based on stomach structure and feeding ecology. Later Hofmann documented variation on the entire digestion tract between the three different classes (Hofmann, 1989; Ditchkoff, 2000).
The three major classes distinguished by Hofmann, are Concentrate Selectors or Browsers (CS)*, Intermediate Mixed feeders (IM) and Grass- and Roughage eaters or Grazers (GR) (Hofmann, 1989).

Within this classification browsers form a complicated group, because relatively a lot of problems occur among captive browsers. Problems such as affections of the digestive tract and peracute mortality syndrome (sudden death) (Fowler, 1993; Clauss et al., 2001; Clauss et al., 2003;). These problems are also caused by a lack of knowledge about browser-nutrition.
Due to an unnatural diet ‘selectivity is highly reduced and the physiological (or metabolically induced) foraging frequency/feeding rhythm has been changed. There is a lack of stimuli to trigger the sequence/cascade of physiological, biochemical and morphological responses acquired (“programmed”) during co-evolutionary processes’ (Hofmann, 2000). These cause that the natural digestive tract changes. For example, it has been shown that in comparison with data from free-ranging, wild ruminants literally all zoo ruminants had drastically reduced rumen papillary surface enlargement factors (SEF) due to acidotic alterations, several had microabcesses, erosions, etc. (Marholdt, 1991; Marholdt and Hofmann, 1991: In Hofmann, 2000).
More clarity is required about the differences between browsers and grazers.

It is known that the variation in shape and chemical composition of plants has led to various anatomical and behavioural adaptations of herbivores (Shipley, 1999).
When looking at the differences in digestion between grazers and browsers, Shipley (1999) found that grazers tend to have larger, more muscular, subdivided rumen/reticulum, and a smaller opening between the reticulum and omasum than browsers. This adaptation might serve to slow down the passage of digesta to lower tract, giving more time for fermentation of cellulose.
Because a greater proportion of the grass cell wall is cellulose (Shipley, 1999; Van Wieren, 1996), this adaptation would presumably allow grazers to digest the cell wall more thoroughly than browsers.

* In this report the terms Browsers and Concentrate Selectors (CS) are used both to represent the same category of ruminants
In contrast to grasses, most browses contain less cell wall-contents. Fibers within the cell wall of browse are more lignified (Shipley, 1999; Van Wieren 1996; Van Soest 1996) and indigestible, so the smaller rumen of browsing animals should allow indigestible food particles to flow more rapidly through the tract. This rapid flow should promote a higher food intake (Shipley, 1999).

Captive browser problems as mentioned above are presumably partly related to the diet offered. Zoos insufficiently take into account the different nutritional requirements of browsers. The ingredients in a browser diet are more based on the diet of grass- and roughage eaters.

The fact that there is a difference in nutritional requirements for browsers has lead to the development of a new concentrate called Hope Farms “Browser pellet”, developed by the European Zoo Nutrition Centre (EZNC) and Arie Blok Diervoeding, which should meet the requirements of CS in a better way. The nutrient composition of the Browser pellet is identical to a concentrate developed for grazers, but one of the fiber sources is Boskos, instead of grass products. Boskos, also named bush feed, is a concentrate consisting of Acacia-, Dichrostachus-, Combretum- and Grewia-species from South Africa (Forman, 2003).

There is a need to test whether the Browser pellet is more suitable for CS.
The nutritional value of a feed is determined by the following factors (Van Soest, 1994; Mc Donald et al., 1995):
  • The availability of nutrients.

  • The ability of a food to supply energy.

  • Intake capacity

Because the digestibility of a feed is related to these factors, it is used to determine the nutritional value. Digestibility has few negative effects of variation (between diets and between individual animals) and therefore is most used (Van Soest 1994).
High digestibility yields more available nutrients for passive or active transport in intestinal absorbtion. Another benefit of increased digestibility is less food is needed to meet energy and nutrient requirements (Hand, et al., 2000).

Generally, when determining the apparent digestibility, classical techniques for digestibility studies are used in which individual feeding and total faecal collection are carried out. These techniques are often not practical with zoo animals; therefore a need exists for a more suitable method to determine the digestibility of a feed.
In this study the digestibility of the Browser pellet is tested on Giraffes (Giraffa camelopardalis), as a standard for determining the nutritional value. The giraffe (Giraffa camelopardalis) is used as a model for the browsing population.

Literature review

Material and methods

In this chapter an explanation is given on the material and methods used for this research. First in paragraph 2.1, the type of research design is explained, and next the animals and their diets are described (paragraph 2.2). The collecting, storing and pre-processing of the foodstuff and of the faeces is described in paragraph 2.3 and 2.4 respectively. Paragraph 2.5 explains the laboratory analyses that were used. In paragraph 2.6 the calculation methods are presented. Finally in paragraph 2.7, the data analysis techniques used are described.


In this chapter, first, the results of the laboratory analyses are summarized, in which the nutrient compositions of the different feed- and faecal samples are presented. Second, the mean feed intake and nutrient intake of the giraffes are presented. Finally, the digestibility coefficients are presented, calculated with the nutrient composition- and intake results


In paragraph 7.1 the values of the laboratory analyses will be compared with values found in literature, to check the reliability of the laboratory analyses. The methods used for calculating feed intake will be discussed in paragraph 7.2. In paragraph 7.3 the results of the apparent digestibility will be discussed.


In this chapter the main conclusion will be given with respect to the research question stated in the introduction:

Is there a difference in the digestibility coefficients for the components Gross Energy (GE), Dry Matter (DM), Crude Protein (CP), Crude (EE), Crude Fiber (CF), NDF and ADF of the Browser pellet compared to the original concentrates?

From the results it can be concluded that:
  • In both zoos, the digestibility of Crude Protein and Ash are significantly higher when the Browser pellet was fed, compared to the original concentrates.
  • The other components had no significant difference in digestibility when the Browser pellet, respectively the original concentrate(s) was/were fed.

Practical implication
During the period when the ration with the Browser pellet was fed;
  • The Crude protein and Ash digestibility increased;
  • The digestibility of the other components did not decrease;
  • The quality of the faeces was not decreased;
  • The Dry Matter intake did not change, compared to the other periods;

Based on these results it can be concluded that the Browser pellet is better suited for giraffes than the original concentrates.


Observing the giraffes made it possible to collect faeces of individual animals kept as a group. Using ADL as indicator, the total amount of faeces produced could be calculated. Also individual intake was calculated from animals, which were fed as a group. In this research these two methods were found useful in revealing differences in digestibility. With these methods digestibility trials can therefore be conducted in a zoo setting.

What causes the differences in digestibility between the zoos is not quite clear. By doing further research on the ingredient and nutrient composition of the diet, this can be explained. For example, it is possible interactions took place between nutrients of foodstuffs in the diet, giving the effect that with the Browser pellet the whole diet is better digested.

During this research the Browser pellet was fed constantly for a period of ten days, in which it was consumed well by all giraffes. To determine the suitability of the Browser pellet it is necessary to investigate the effect over a longer period of time.
The digestibility of a feed is related to, among others, the intake capacity. The intake capacity is also better to determine over a longer period of time.
When feeding the Browser pellet on the long term, changes in condition of the animals can also be investigated.

The suitability of the Browser pellet can be further studied by comparing the nutrient intake of the giraffes’ diet with the nutrient recommendations for this species.

In this research the giraffe (Giraffa camelopardalis) has been used as a model for browsers. To be able to say something about the suitability of the Browser pellet for browsers in general, the research has to be carried out on other browsing species because differences between species exist. These results have to be compared to one another.


  • Beemster, C.J.M., Heijden, L.J.M. van der en K.F.A.M. Hulshof, 2001, NEVO-tabel: Nederlandse voedingsstoffenbestand, Stichting Nevo, Zeist.

  • Church, D.C., 1976a, Digestive Physiology and Nutrition of Ruminants, Metropolitan Printing Co., Portland, Oregon, Volume 1- Digestive Physiology, second edition.

  • Church, D.C., 1976b, Digestive Physiology and Nutrition of Ruminants, Metropolitan Printing Co., Portland, Oregon, Volume 2- Nutrition, second edition.

  • Clauss, M., and E. Kienzle and J.-M. Hatt, 2003, ‘Feeding practice in captive wild ruminants: peculiarities in the nutrition of browsers/concentrate selectors and intermediate feeders’, A review, Zoo Animal Nutrition, p. 27-52, Filander Verlag, Fÿrth, volume II.

  • Clauss, M., et al., 2001, ‘Comparative Use of Four Different Marker Systems for the Estimation of Digestibility and Low Food Intake in a Group of Captive Giraffes (Giraffa camelopardalis)’, Zoo Biology, 20, p. 315-329.

  • Centraal Veevoederbureau, 1992. Handleiding voederwaardeberekening ruwvoeders: aanvullende handleiding 1996, Lelystad.

  • Centraal Veevoederbureau, 2003, Veevoedertabel: gegevens over chemische samenstelling, verteerbaarheid en voederwaarde van voedermiddelen, Centraal Veevoederbureau Lelystad.

  • Ditchkoff, S. S., 2000, A decade since “diversification of ruminants”:
    has our knowledge improved?
    Oecologia 125, p.82–84

  • Fokkinga, A., and M. Felius and A. Cameron, 1999, Koeboek, Houten, second edition.

  • Forman, M., 2003, Grazer- en browserbrok, Ontwikkeling aanvullende brok voor grazers en browsers, final thesis, Hogeschool Inholland afdeling Dier- en Veehouderij, Woerden.

  • Fowler, M.E., and R.E. Miller, 2003, Zoo and wild animal medicine, St. Louis, Saunders, fifth edition.

  • Hand, M.S. et al., 2000, Small Animal Clinical Nutrition, Topeka, Kan, fourth edition.

  • Hofmann, R.R., 2000, ‘The structure of digestive systems in the feeding of mammals: a comparative approach’, Zoo Animal Nutrition, p. 163-181, Filander Verlag, Fÿrth, volume I.

  • Illius, A.W. and I.J. Gordon, 1991, ‘Prediction of intake and digestion in ruminants by a model of rumen kinetics integrating animal size and plant characteristics’, J. Agric. Sci., Cambridge, 116, p. 145-157.

  • Kool, K. and E. Smit, 2000, Op een houtje bijten, final thesis, Van Hall Instituut, Leeuwarden.

  • Kuiper, D.G., 1994, Chemische diervoederanalyse, Module DMH08/LBH09, dictaat 05077, Van Hall Instituut, Leeuwarden.

  • McDonald, P., et al., 1995, Animal nutrition, Longman Scientific & Technical, Singapore, fifth edition.

  • Parker, D.M., R.T.F. Bernard, S.A. Colvin, 2003, ‘The diet of a small group of extralimital giraffe’, African Journal of Ecology, 41, p. 245-253.

  • Pond, W.G., and D.D.C. Church and K.R. Pond, 1995, Basic Animal Nutrition and Feeding, John Wiley & Sons, New York, fourth edition.

  • Robbins, C.T., 1993, Wildlife Feeding and Nutrition, Academic Press, Inc., San Diego, second edition.

  • Sandargas, R.A., and L.C. Summer, 1996, ‘Single Subject (Small N) Research Designs and Zoo Research’, Zoo Biology, 15, p.175-181.

  • Shipley, L.A., 1999, Grazers and Browsers: How digestive morphology affects diet selection,

  • Short, Henry L., and Robert M. Blair and Charles A. Segelquist, 1974, ‘Fiber composition and forage digestibility by small ruminants’, J. Wildl. Manage., 38 (2), p. 197-209.

  • Skinner, J.D., 1990, The Mammals of the Southern African Subregion, University of Pretoria, Republic of South Africa.

  • Van Soest, Peter J., 1994, Nutritional Ecology of the ruminant, Cornell University Press, Ithaca, second edition.

  • Van Soest, Peter J., 1996, ‘Allometry and Ecology of Feeding Behavior and Digestive Capacity in Herbivores: A Review’, Zoo Biology, 15, p.455-479.

  • Van Wieren, S.E., 1996, ‘Nutrient extraction from mixed grass-browse diets by goats and sheep’, Digestive strategies in ruminants and nonruminants, Thesis Landbouw Universiteit Wageningen, Netherlands, p. 67-80.