The Giraffe inside out
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
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 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.
- Is there a difference in digestibility coefficients1 for the components Gross Energy (GE), Dry Matter (DM), Crude Protein (CP), Crude Fiber (CF), Neutral Detergent Fiber (NDF) and Acid Detergent Fiber (ADF) of the ration in which Hope Farms Browser pellet2 is used compared to the ration with the original concentrates3?
- That proportion which is not excreted in the faeces and which
Coefficient (ADC) is, therefore, assumed to be absorbed by the animal. Expressed in terms of DM and as a coefficient (McDonald et al, 1995).
(ADCnutrient = ( Nutrient consumed-Nutrient in faeces)
In this report the term digestibility refers to the apparent digestibility.
- The commercial, pelleted concentrate for captive browsers, developed by the European Zoo Nutrition Centre (EZNC) and Arie Blok Diervoeding, produced with the brand name Hope Farms. Browser pellet is the commercial name of this concentrate, whereas the word pellet refers to the shape of the concentrate.
- The commercial, pelleted concentrates that are fed to the captive browsers as part of their diet up till now. These concentrates are not specifically developed for browsers. In Artis Zoo the original concentrates fed are Basisbrok Artis, Euro Groen, EQuiral structuurmix and Grasbrok. In Burgers Zoo this is Zoo pellet HE.
3Original concentrates The commercial, pelleted concentrates that are fed to the captive browsers as part of their diet up till now. These concentrates are not specifically developed for browsers. In Artis Zoo the original concentrates fed are Basisbrok Artis, Euro Groen, EQuiral structuurmix and Grasbrok. In Burgers Zoo this is Zoo pellet HE.
The giraffe as a browsing species
CS are unable to tolerate large amounts of fiber in their diet and are thus limited to selective feeding on low fiber portions of plants (Van Soest, 1996). Hofmann (1989) points out that selective ruminants have comparatively larger lower digestive tracts relative to the rumen, emphasizing perhaps a reduced role for the rumen
Figure 1 Classification and general information of Giraffa camelopardalis
Based on its feeding habit the Giraffe (Giraffa camelopardalis) is classified as a Browser.
Giraffes utilise a wide range of food plants, but will graze occasionally on fresh sprouting palatable grasses (Skinner, 1990). Hall-Martin (1974) showed that, in the Eastern Transvaal, their food varies with the time of the year. During the hot wet months (November-March), when there is a plentiful supply of browse, they feed mainly on Acacia, Combretum,
Terminalia and Ziziphus Various species of Acacia
are the most important and preferred food plants for giraffe (Giraffa camelopardalis). During the hot dry months from August to November, when the leaf mass is drastically reduced, they will turn to evergreens or semi-deciduous species such as Euclea, Maytenus, Schotia and Diospyros. The fruits of the Acacia and Combretum are included in their diet, as well as the flowers of trees. At thistime they tend to take more woody material than they do when fresh leaves are available and will utilise species not taken at other times of the year, such as mopane, (Colophospermum mopane).
According to Parker at al. (2003) the diet of extralimital giraffes (Giraffa camelopardalis) is compromised of 14 plant species, the most important species being Rhus longispina (47.9%), Acacia karroo (25.7%) and Euclea undulate (17.6%). The relative importance of Rhas longispina, Acacia karrooand Tarchonanthus camphorates fluctuates seasonally. Acacia karroo thickets were utilized most, with alternative habitats utilized more often in winter than in summer.
In relation to other browsers, the giraffe (Giraffa camelopardalis) has a greater digestive capacity than the smaller browsers, and for its size should be more tolerant to lower quality browse (Van Soest, 1996).
Difference between Grass and Browse
The differences between grass and browse are seen in cell structure, plant chemistry, plant architecture, and plant dispersion (Table 1) (Shipley, 1999).
Table 1 A relative comparison of chemical and structural differences between grasses (monocots) and browses (herbaceous and woody dicots) (Shipley, 1999).
Grasses tend to have a thicker cell wall than browses, and their cell walls consist mainly of slowly-digestible plant fibers such as cellulose (Shipley, 1999; Van Wieren, 1996). Within the cell wall, however, browses usually contain more indigestible fibers such as lignin (Shipley, 1999; Van Wieren 1996; Van Soest 1996). Grasses also tend to have a higher silica concentration that reduces the ability to digest fiber. In contrast, browses tend to have more phenolics, including tannins that can reduce protein digestibility, terpenes that can reduce dry matter digestibility, and toxins such as alkaloids (Robbins, 1993).
Because a greater proportion of grass cell is cellulose, this adaptation would presumably allow grazers to digest the cell wall more thoroughly and obtain more energy per unit of food. However, if food moves more slowly through the digestive tract, food intake may also decline.
In contrast, most browses contain less cell wall, and fibers within their cell wall are more lignified 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).
Van Wieren (1996) described some differences in chemical composition between grass and browse (Table 2). He also shows that browse contains more lignin and that DM digestibility is lower in Browse (tested on sheep and goats). NDF mainly consists of cellulose, hemicellulose and lignin. Because grass has a higher NDF content, with a smaller amount of lignin in ADF, grass contains more cellulose and hemicellulose compared to browse.
Table 2 Chemical composition of browse and grass samples (Van Wieren, 1996).
Lignin marker method
Material and methods
In the baseline (A / A) periods the research subjects were fed on a diet that contained the original concentrates. In this research the experimental condition (B) is the diet in which the Browser pellet is the substitute for the original concentrate(s) that were fed. In all the periods (A / B / A) the other components of the diet were kept as stable as possible. In the adaptation periods, the animals were accustomed to another concentrate, to allow adaptation of the micro-organisms and adjust feed intake to a stable level (Church, 1976a).
Each adaptation period consisted of four days in which the original concentrates and the Browser pellet were mixed to accustom the animals, and five days adjusting, when only the Browser pellet (first adaptation period) or the original concentrates (second adaptation period) were fed in a constant amount.
A schedule of the different periods is presented in figure 2.
Figure 2 Time schedule datacollectingperiod
A period of five days (120 hours) to adjust feed intake into a stable level was chosen, because the mean retention time of giraffes is 80-90 hours according to Illius and Gordon (1991) and 34-48 hours, according to Clauss (1998: In Hofmann, 2000). Also, five days was practical considering the time schedule.
Animals and diet
Table 3 Location, Age, Sex and Life stage of the giraffes (Giraffa camelopardalis) (may, 2004)
The three giraffes of Artis were kept as a group, but faeces were collected individually through observing the manuring of the animals during the daytime. During the day, they were kept in an outdoor enclosure with a sand surface. They shared this enclosure with seven Springbucks (Antidorcas marsupialis) and three Waterbucks (Kobus ellipsiprymnus). At night the giraffes were kept together in the inside enclosure.
In Burgers Zoo the giraffes forming the group (with research subject number 7) and Cas were kept together during the day in an outside enclosure of approximately 8 hectares. They shared this enclosure with about seventeen Grants Zebras (Equus burchelli bohmi), nine Blue Wildebeasts (Connochaetes taurinus), eleven Waterbucks (Kobus ellipsiprymnus), four Blesboks (Damaliscus dorcas philllipsi), three Roan Antelopes (Hippotragus equinus) and three White Rhinoceroses (Ceratotherium simum). During the night the group was housed together, with Cas housed separately. Floor and Fleur were kept together in an inside enclosure during day and night, Uwe was also kept in an inside enclosure during day and night.
Mirna, was kept separate from the group in an inside enclosure during the second adaptation period and gave birth to a healthy calf during period A.
As described in paragraph 2.1, in period A and A the giraffes were fed the original concentrates. In period B the original concentrates were replaced by the Browser pellet.
The amount of feed offered was kept as similar as possible between the three periods. Before the periods started a list was drawn, which described the usually offered diet, to promote a constant amount of feed offered by all zookeepers.
Daily feed intake was measured by weighing the feed offered by the zookeepers, every other day, for three days per period. Leftovers were re-weighed and were subtracted. Per research subject the mean intake of the three days was calculated.
Lucerne intake was measured at one day during each period. Lucerne placed in racks was weighed and the next day the leftovers in the racks and on the floor were re-weighed. Browse intake was not measured, because it was assumed to be the same over all research periods.
Figure 3 Diet contents fed to the research subjects
In Artis, individual feed intake was determined by how the zookeepers divided the food among the three giraffes. Otherwise by measuring the intake of the whole group, and divide this by three, assuming that all animals had similar appetite and access to the food.
Figure 3 presents the diet contents of the giraffes used in this study.
In the outside enclosure in Burgers Zoo the giraffes had little access to browse, because bushes and trees were fenced with electric wire. The browse intake and composition were neglected. The vitamin E (500.000 IE/kg) offered to these giraffes was omitted, since the amount of fed was 5 gram per animal, which in a diet of several kilograms was considered irrelevant.In both Zoos water was provided ad libitum. The exact composition of the diets is presented in Table 5 and 6 of chapter 3.2 Feed intake. The original concentrates fed to the giraffes in period A and A were replaced by the Browser pellet in period B.
The nutrient contents of the different concentrates (including the Browser pellet) as stated by the producer are presented in appendix III.
Collecting, storing and pre-processing foodstuffs
After DM determination, the duplicate foodstuffs were ground with a Retsch GMbH, type SR2. Some foodstuffs were not homogeneous after grinding and were then ground for a second time with a Fritsch puluerisette, type 14702. The samples were collected in jars and labelled.
Collecting, storing and pre-processing faeces
The faeces of the giraffes from Burgers Zoo were collected from the stables in the morning.
The giraffes in Artis, kept as a group, where observed by Continuous recording during the daytime, when they were housed in the outside enclosure, by which individual faeces collection was made possible.
All faeces were stored after collection, at -20°C until the end of the third period (A).
At the end of the third period (A) all faeces was defrost in a refrigerator before drying.
The faeces of each period were put together, carefully cleaned by hand to remove sand or other ground cover. The faeces were mixed thorough, resulting into three different samples (one for each period) per subject.
All faeces samples were dried in an oven at 60°C for 72 h, to determine DM content (see paragraph 2.5.2 Dry matter determination), after which the samples were ground with a food processor and then ground with a Fritsch puluerisette, type 14702. The samples were collected in jars and labelled.
All analyses were performed in duplicate, and a deviation between the duplicates of 5% or less was permitted. Except for CP, were a maximum of 2% was permitted. Figure 4 presents an example of calculating the deviation between the duplicates
Figure 4 Calculation example of determining the deviation between two duplicates.
More detailed information of all analyses is provided in the next paragraphs.
Mean feed intake
For each period (A/B/A) feed intake (in g/day) was determined, by taking the average feed intake of three days in each period. The Lucerne consumption was determined over one day per period. The standard deviation (SD) was calculated too.
Mean nutrient intake
The mean nutrient intake (g/day) was calculated by multiplying the feed intake (g DM/day) by the nutrient composition (% or KJ/kg) of the foodstuff. All values are calculated on DM base. In figure 5 an example of how the mean nutrient intake was calculated is given
Figure 5. Calculation example of determining mean nutrient intake.
In this study it was impossible to collect total faeces, therefore the internal indicator lignin was used. To calculate the digestibility of a nutrient, the following formula was used (Pond et al., 1995);
Apparent digestibility coefficient= 1 ((%ind.fd / %ind.fc) x (%nutr.fc / %nutr.fd)) (5)
Where ind. stands for indicator; fd for in food; fc for in faeces and nutr. for nutrients. The percentage of indicator and nutrient in food and faeces are on DM base. The percentage of nutrients in food was calculated by dividing the mean nutrient intake of a foodstuff by the total mean intake of the diet.
Laboratory analyses results
Table 4 Nutrient content summary of food- and faeces samples (DM base).
Of each zoo one sample of the Browser pellet was analysed. The values between these two samples do not differ drastically. In Artis more different foodstuff were fed to the giraffes.
The ash content of the faeces from the giraffes in Artis (Grena, Oranya, Jabu) is higher compared to the ash content of the faeces from the giraffes in Burgers Zoo.
Table 5 Feed intake (Mean±SD) in g/day per period by Giraffes in Artis (as fed).
Table 6 Feed intake (Mean±SD) in g/day per period by Giraffes in Burgers Zoo (as fed).
In the B period the original concentrates are replaced by the Browser pellet.
Table 7 Mean DM nutrient intake by the giraffes (g/day and KJ/day).
The CF intake is higher in the B period, when the ration with the Browser pellet was fed.
When comparing between the three periods (A,B,A), the ADL intake of the giraffes from Artis was higher in the B period (when the Browser pellet was fed). In Burgers Zoo ADL intake was lower in the B period compared to the periods in which the original concentrates were fed.
When looking at the DM intake between the different periods, the tests show that;
There is no difference in DM intake, when the ration with the Browser pellet or respectively the ration with the original concentrates was fed (P=0.687; F=0,390; n=7).
There was a difference in DM intake between the two zoos (P<0.001; F=368.445; n=7).
Table 8 Digestibility coefficients (DC) of nutrients by giraffes calculated over three periods
Per component, the differences between digestibility coefficients in the different periods are tested and the differences between the digestibility coefficients of the two zoos are tested.
Gross energy digestibility
In figure 6 the digestibility coefficient of Gross Energy of the research subjects are presented.
Figure 6 Mean Digestibility Coefficients of Gross Energy of each zoo.
The effect of the concentrate fed on the digestibility is different between the both zoos (P<0.001; F=28.527; n=7). Figure 6 shows that the Gross Energy digestibility in period B decreases in Burgers Zoo while it increases in Artis.
As shown in figure 6, the mean Gross Energy digestibility of the giraffes in Artis (n=3) is lower than the mean Gross Energy digestibility of the giraffes in Burgers Zoo (n=4) (P=0.003; F=29.438).
Dry matter digestibility
In figure 7 the digestibility of Dry Matter of the research subjects are presented.
Figure 7 Digestibility Coefficients of Dry matter per research subject.
There is no significant (P=0.210; F=1.829) interaction between the concentrate fed and the zoo, meaning both zoos show the same trend on dry matter digestibility when the ration with the Browser pellet, respectively the ration with the original concentrate was fed.
There is no difference in Dry matter digestibility between the ration with the Browser pellet and the ration with the original concentrates (P=0.073;F=3.440; n=7).
The mean Dry matter digestibility between the both zoos is significantly different (P<0.001; F=8.858; n=7). The mean Dry matter digestibility of the giraffes in Artis (n=3) is higher than the mean Gross Energy digestibility of the giraffes in Burgers Zoo (n=4), as shown in figure 7.
Crude protein digestibility
In figure 8 the digestibility of Crude Protein of the research subjects are presented.
Figure 8 Digestibility Coefficients of Crude protein per research subject.
The results show that there is an interaction effect between the zoo and the different periods (P=0.028; F=5,257; n=7), meaning that the effect of the concentrate fed on the digestibility is different between the both zoos. However, figure 8 shows that in both zoos the Crude Protein digestibility in period B increases compared to the other periods. This increase is more striking in Burgers Zoo, which can explain the interaction effect.
Therefore, the difference in Crude Protein digestibility between the three periods was tested individually per zoo. In Artis, the Crude Protein digestibility is significantly higher in the ration with the Browser pellet compared to the ration with the original concentrates (P=0.015; F=14.217; n=3).
In Burgers Zoo the Crude Protein digestibility is also significantly higher in the ration with the Browser pellet (P<0.001; F=49.274; n=4).
In figure 9 the digestibility of Ash of the research subjects are presented.
Figure 9 Digestibility Coefficients of Ash per research subject.
There is a difference in Ash digestibility between the ration with the Browser pellet and the ration with the original concentrates (P<0,001 with F=30,605). Figure 9 shows that the ash digestibility increases when the ration with the Browser pellet was fed.
Both zoos show the same trend on Ash digestibility when the ration with the Browser pellet, respectively the ration with the original concentrates was fed (P=0.159; F=2.218; n=7).
The mean Ash digestibility between both zoos does not differ significantly (P=0.963; F=0.002; n=7).
Crude fiber digestibility
In figure 10 the digestibility of Crude Fiber of the research subjects are presented.
Figure 10 Digestibility Coefficients of Crude fiber per research subject.
The effect of the concentrate fed on the digestibility is different between the both zoos (P=0.027; F=5.296; n=7). Figure 10 shows that the Crude Fiber digestibility in period B decreases in Artis while it increases in Burgers Zoo.
Figure 10 shows that the giraffes in Artis have significantly higher Crude fiber digestibilities, compared to the giraffes in Burgers Zoo (P<0.001; F=725.066).
Neutral detergent fiber digestibility
In figure 11 the digestibility of NDF of the research subjects are presented.
Figure 11 Digestibility Coefficients of NDF per research subject.
The effect of the concentrate fed on the digestibility is different between the both zoos (P=0.023; F=5.589; n=7). Figure 11 shows that the NDF digestibility in period B decreases in Artis while it increases in Burgers Zoo.
Figure 11 shows that the giraffes in Artis have higher NDF digestibilities, compared to the giraffes in Burgers Zoo (P<0.001; F=125.365).
Acid detergent fiber digestibility
In figure 12 the digestibility of ADF of the research subjects are presented.
Figure 12 Digestibility Coefficients of ADF per research subject.
The effect of the concentrate fed on the ADF digestibility is different between the both zoos (P=0.001; F=15.450; n=7). Figure 12 shows that the NDF digestibility in period B decreases in Artis while it increases in Burgers Zoo.
Figure 12 shows that the giraffes in Artis have higher ADF digestibilities, compared to the giraffes in Burgers Zoo (P<0.001; F=167.239), which was also shown in ADC of the components NDF and CF.
Only the GE content of the Browser pellet was found as stated by the producer. The GE values from this study are 2443 KJ/kg and 2504 KJ/kg higher than the producer cites. Using different laboratory methods for determining GE may cause this difference.
When looking at DM content of the samples determined in this study compared to the literature, there are no striking differences, except for pulp and bread. The pulp DM content in this study is lower (41,48%) than was stated by the producer, because the pulp was soaked in water before it was analysed. Bread had higher DM content in our study, this difference can be explained by the fact that the bread was stored for a while. Endive, apple and carrot were fresh when put into the oven for drying. Both endive and apple became somewhat filthy because of the rusty drying bakes. This could have affected the analyses, DM values do not show a striking difference with the literature. Both apple and carrot became somewhat mouldy in the oven (most of it could be removed).
Within Crude protein determinations, large differences where found in Oat flakes with St. J. Bread, and Lucerne. Oat flakes with St. J. Bread was mixed at Artis Zoo, therefore the nutrient content was determined by taking one sample of these mixed ingredients. The CP content is 11,35%, whereas in the literature a value of 5,2% is found (this value reflects an average nutrient content of Oat flakes and St. J. Bread). The difference can be caused by the ratio of mixing Oat flakes with St. J. Bread. The Lucerne used in this study contains 10,77%; 9,20%; and 9,37 CP, whereas the literature cites 14,2% CP. The slightly lower values of CP can be caused by the quality of the Lucerne; in both zoos the Lucerne was old. When Carrot was grounded with the Fritsch puluerisette, it smoked, pieces could have burned. This might have affected the protein analyses among others, but the values in the literature do not show much deviation.
A large difference in the ash contents between this study and the literature is found in Apple and Endive. Determining DM content and grinding of Apple and Endive was difficult, this could be the cause of the differences found. The largest number of deviations between the duplicates occurred when determining the ash percentage.
Most differences between nutrient contents obtained in this study and the literature are seen in CF. Grasbrok contains 5,77% more CF in this study than the literature cites. Oat flakes with St. J. Bread contain 14,52% less CF according to this study.
Linseed with multivitamin contains 10,05% more CF than the literature cites, this difference can be due to the fact that multivitamin has not been taken into account in the literature value, but it was determined in our study as mixed sample. Carrot contains 7,96% and 9,43% more CF in this study compared to the literature, this might be caused by the dry matter determination and the grinding of the sample. Endive and Apple also show striking differences in CF values (Endive CF is 44,58% lower in this study compared to the literature; Apple is 8,17% lower). As said before this could be caused by the difficulties which occurred in DM determination. The Lucerne CF content in this study is 19,79; 16,91 and18,25% higher than was found in the literature. The CF determination is probably not overrated, because not all the samples in this study had higher CF contents in this study compared to the literature.
NDF values found in the literature differ from the values found in this study for Oat flakes with St. J. Bread (36,33% lower in this study) Linseed with multivitamin (22,52% higher), and Oat from Burgers Zoo (8,17% higher). The difference in the two first samples can be caused by the fact that it were mixed samples, as described before. The literature reflect a value for Oat, this deviation might be caused by the difference in processing the Oat. ADF an ADL of Oat flakes with St. J. Bread and Linseed with multivitamin also differ in composition between this study and the literature.
Further, it should be noted that the nutrient composition of the Browser pellet obtained from this study closely reflects the composition subscribed by Hope Farms.
Measuring feed intake
Lucerne and Pea straw intake were determined over a relative small period of time (one day per period) and the intake was difficult to determine, because of the loss of Lucerne from the racks. In Burgers Zoo the Lucerne in the outside enclosure has not been weighed, and therefore estimated by the amount of Lucerne that the zookeepers placed in the outside enclosure every day. Other animals, which were also kept in the outside enclosure, might have had access to this Lucerne. Therefore the Lucerne intake by Cas and the Group might be overestimated (the other giraffes were kept inside during the day).
It was observed that Jabu, one of the giraffes from Artis, ate straw from the ground. The quantity of straw intake was not measured. The ADC might therefore be to high, because the nutrients from straw are measured in the faeces, but not in the intake
Table 9 Nutrient composition of Elm and Willow (Kool and Smit, 2000).
According to Short, Blair and Segelquist (1974) especially mature woody twigs of browse plants are poorly digested.
The assumption was made that browse intake by the giraffes did not change during the three periods, but this could not be demonstrated. It could therefore be possible that the giraffes ate more (or less) browse when the Browser pellet was fed, affecting the ADC.
It is difficult to compare the food intake of the giraffes from the two zoos, because the animals differ in age, sex, life stage, and comparing individual animals with a group results in certain assumptions. However, an attempt was made to calculate individual food intake, by dividing the mean intake of Floor and Fleur by 1.5 and the group by 8. The results show that there was no difference in DM intake between the three periods. However, a significant difference between the both zoos was found. Figure 13 shows that the mean DM intake in Burgers Zoo is lower compared to Artis. This may cause the different digestibility coefficients of GE, DM, CF, NDF and ADF, found between both zoos. The intake of the components GE, CP, ASH, CF, NDF and ADF are presented in appendix IV.
Figure 13 Mean DM intake (g/day/animal) of the giraffes from Artis and Burgers Zoo in the three different periods, with Standard errors (SE).
The chemical compositions of the different concentrates used in this study are compared in figure 14. This figure shows that there seems to be difference in chemical composition. The mean concentrate of Artis has lower nutrient contents compared to the mean Browser pellet, except for NDF. The amount of fibre in the food is presented in table 4 in paragraph 3.1 Laboratory analyses results.
Figure 14 Chemical composition of the concentrates fed in period A/B/A.
One other discussion point is that Jabu from Artis Zoo had diarrhoea for some days in period A and B, which may have influenced the digestibility coefficient of DM, this is not clear from the results.
The DM of the faeces could also be influenced by the storing and pre-processing method. However, these were kept as similar as possible for all research subjects and periods.
Assuming that dietary factors required by rumen micro-organisms are present in adequate amounts, one other major factor related to protein utilization appears to be that of solubility, both in the rumen and in the gut. For ruminants, the degree of solubility of natural plant or animal proteins is directly correlated to the rate at which ammonia is released in the rumen. Proteins may be less soluble when heat-treated or chemically treated to reduce solubility (Church, 1976b).
Tannins, a group of plant defences, can dramatically reduce apparent digestibility of protein. The magnitude of reduction varies depending on the animals ability to neutralize the tannins protein-binding capacity (Robbins, 1993).
One possible explanation for the increased digestibility when the ration with the Brower pellet was fed is that the protein source of the Browser pellet is of better quality. For ruminants, Crude protein is very important for a good break down of Crude Fiber and for the production of micro-organisms in the rumen (Fokkinga, Felius and Cameron, 1999).
Protein quality is generally defined as the ability of a specific protein to provide essential amino acids in the required amounts to a given animal. Protein digestibility is not the only factor determining the protein quality; there is for example also a high correlation between the biological value of the protein and numbers of ruminal bacteria (Church, 1976b).
And a dietary access of lipids will inhibit rumen micro-organisms (Mc Donald et al., 1995). The content of crude fat has not been determined in this study. According to Hope Farms, the Browser pellet contains 5,5% of crude fat (DM), which is a relative small amount. Zoo pellet HE contains 5,4% crude fat, and the mean concentrates in Artis contain 4,2% crude fat on DM base. Therefore the inhibition of rumen micro-organisms may be insignificant.
The measure of importance is therefore true digestibility (Mc Donald et al., 1995). The two negative outcomes of the digestibility coefficient of ash can also be explained by this fact.
Other, very reasonable explanations for the negative coefficients are that the manure was polluted with sand and the consumption of sand. In Artis it was observed that animals, especially Jabu, sometimes ate from the ground, which was covered with sand. The fact that the faeces samples from the giraffes in Artis showed higher Ash percentages compared to the faeces of the giraffes from Burgers Zoo support these observations.
The results show that there is significant evidence that the ash digestibility is higher in both zoos, when the Browser pellet is fed. But according to Mc Donald 1995, the digestibility coefficient of ash has little significance. The percentage of ash in the Browser pellet is a bit higher, compared to the original concentrates (figure 13), and when looking at the nutrient intake per research subject (table 7 and Appendix IVb), in all B periods the Ash intake is higher.
Crude Fiber, NDF and ADF
Digestibilities of NDF are functions of the relative concentration of structural digestion inhibitors (particularly lignin, cutin, and silica), type of gastrointestinal tract, and rate of passage. The digestibility of NDF decreases in ruminants as lignin and cutin concentrations increase (Robbins, 1993). The results show that the giraffes in Artis have higher mean NDF, ADF and CF digestibilities per period, compared to the giraffes in Burgers Zoo. Table 7 (nutrient intake) shows no extreme difference in ADL intake when comparing between both zoos, although this is difficult to compare between different animals, as said before. Therefore, the ADL content probably could not cause the difference in NDF digestibilities. Although the original concentrates fed in Artis have higher NDF content than the Browser pellet and the Zoo pellet HE (figure 13), the digestibility of NDF is still higher when the Browser pellet is fed in Artis, compared to Burgers Zoo.
Another striking difference is that the digestibility in period B, when the Browser pellet is fed, is lower in Artis and higher in Burgers Zoo for the components CF, NDF and ADF. This might be explained by the ADL intake, which is higher in period B by the giraffes in Artis and lower by the giraffes in Burgers Zoo. The increased lignin intake might have decreased the digestibility.
Other digestibility trials on giraffes (<i>Giraffa camelopardalis</i>)
Table 14 Comparative digestibility data for giraffes (min-max).
DM digestibility of 0,91 is high compared to the other data. This could be explained by the fact that in the study of Clauss, less research subjects were used, giving a bigger chance for failures (SE).
Lignin marker method
Lignin has been used in a comparative study of four different marker systems in a group of captive giraffes (Clauss et al., 2001). In this study lignin turns out to provide the most stringent inter-individual comparisons, and that lignin can be used for giraffe digestibility studies.
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.
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.
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.
has our knowledge improved? Oecologia 125, p.8284 http://www.sfws.auburn.edu/ditchkoff/PDF%20publications/2000%20-%20Oecologia.pdf.