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UGent Faculteit Diergeneeskunde, labo diervoeding

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Abstract bachelor project FBT 2019-2020: Nutrient analysis of feed for production fish in Ethiopia and Bolivia

In order to obtain a sustainable aquaculture, it is important to know the nutrient composition of the fish feed. When a feed is of poor quality, the fish will not efficiently absorb the nutrients and the water will become contaminated with unabsorbed minerals and other nutrients present in the feed. The aim of this research is to determine the quality of different fish feed for the farming of rainbow trout (Oncorhynchus mykiss) in Lake Titicaca, Bolivia and Nile tilapia (Oreochromis niloticus ) in Jimma, Ethiopia. The content of crude fibre, crude fat, crude ash, crude protein and hemicellulose are analysed, using the Proximate and Van Soest analyses. Due to the covid-19 epidemic, only 7 samples from Ethiopia were analysed, including two complete feeds and five ingredients. The results are compared with literature data and the nutritional requirements of the Nile tilapia. The first ingredient, rumen liquor, contains less crude protein than expected. Extremely low percentages of crude fiber, crude fat and crude protein are obtained after the analysis of the second ingredient, molasses. Molasses consists almost entirely of sugars. The third analysed ingredient is brewers’ grains. Brewers grain is rich in protein and fibre. The fourth sample is a locally produced ingredient. Niger seed cake contains a high content of crude protein, crude fat and crude fibre. The last sample consists of wheat bran from which a high protein content has been obtained. In complete feeds, the amount of crude protein and crude fibre does not accord to the nutritional requirements. The results obtained after the Van Soest analyses often differ from the literature data. This is caused by the growing conditions and the growth stage of the cultivated plants. A different composition should be used for the complete feeds, because the results do not meet with the nutritional requirements. In the future, the analyses should be repeated several times per sample in order to obtain representative results. It would also be better to use specific analyses to determine the mineral fraction and the amount of crude protein.



Total fibrous matter (TFM) is a method to analyse both plant and animal fiber. A method to analyse only the plant fiber is total dietary fiber (TDF), this is based on Boisen and Fernandez (1997) and Hervera et al (2007, 2009). Animal fiber may have an important role in the gastro- intestinal health of diverse carnivores and omnivores. It contains hair, skin, tendons, bones and even the exoskeleton of insects. Research in cheetahs has found that animals who are fed with more animal fibers have less gastro-intestinal diseases and less toxic metabolites are formed in the hindgut compared to animals which are fed only plant fibres. The aims of this study are to optimize the already existing TFM method and to validate the new optimized method. It is of great importance that the newly found method works to the fullest.

The used method is based on an in vitro digestion with porcine pepsin and pancreatin as the digestive enzymes. The samples must be incubated at 39 °C. We use this temperature because it’s the physiological temperature of carnivores. After incubation at 39 °C the samples need to be centrifuged. As a result, the desired components precipitate. To know the exact amount of animal fiber, both the TDF and the TFM method must be performed. TDF is a method to analyse only plant fiber. The results from the TFM must be deducted from the TDF to know the exact amount of animal fiber.

First, we increased the concentration of porcine pepsin and pancreatin to be sure that the digestion was optimal. The percentage of fiber for pigfeed was 40 and 35.6 for minced chicks’ sausage. Then the analysis took place in Falcon tubes instead of using Duran bottles. This adjustment increases the surface area for the digestion. Normally the sample is filtered after the digestion, but this is replaced by a centrifuge. With these changes an average of 24% of fiber for the pigfeed and minced chick’s sausage were measured. These results already seem more accurate. Then we did a comparative test to see which method really shows the best results. We used minced chick’s sausage. A filter, centrifuge (3000g), ultracentrifuge (8000g) and the protocol with Duran bottles were compared. 28% of fiber for the centrifuge, 31% for the filter, 32% for the protocol with Duran bottles and 31,8% for the ultracentrifuge were obtained.

Centrifugation appears to be the better method. Finally, we have used various methods to treat the pellet: (1) let it dry in the drying furnace, (2) pour 60°C demineralized water over the pellet, mix well, centrifuge and let the pallet dry in the drying furnace, (3) add ethanol to the pallet and let dry in the drying furnace. If we look at the ash obtained from the pigfeed, only in option 2 there was no ash left. This means that there is no animal fiber in the pellet. So, option 2 seems to produce the most accurate results so far. We can conclude that the method found so far is not yet perfect, so further adjustments will have to be made. A next step is to analyse casein in Falcon tubes (milk protein that should be completely digested) to see if everything would be digested.


To asses the gastrointestinal health of carnivores in captivity, it is important to be able to quantify the amount of dietary fibre in their diet. The Department Animal Nutrition from Ghent University Faculty of Veterinary Medicine developed a new method named ‘Total Fibrous Matter (TFM)’ that can determine the total fibrous fraction including plant derived fibre as well as animal derived fibre, in contrast to the classic ‘Total Dietary Fibre (TDF)’ method which only quantifies plant derived fibres. The aims of this study are first to further optimize the TFM protocol. Secondly to validate the described method. This validation is done by comparing the results of fibre analysis obtained by the traditional TDF method and the new TFM method. The results confirm that the new TFM method quantifies the total fibrous matter including plant- and animal derived fibres. The TFM method also allows differentiation between the soluble and insoluble amount of dietary fibre present in the samples. The results show that the TFM method can detect small amounts of dietary fibre as well, however the accuracy of these results should be improved. Therefore further validation of the method is necessary.


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Abstract bachelorproef 1 2015-2016: Characterization of tannins from tropical plants by spectrophotometry

In Ethiopia, livestock is a very important export product. About 25% of the livestock is used as draft animals. It is crucial that these animals have the necessary strength. Getting the necessary strength could be a challenge during the dry periods in Ethiopia. The animals are forced to feed on branches, shrubs and leaves of the trees instead of grass. The first type of plants are rich in tannins which gives a series of negative effects for the animals. Therefore an inexpensive method is required that allows easy characterisation of these tannins in the different plant species. It must be borne in mind that the availability of laboratory supplies and equipment is very low in Ethiopia. Therefore, a spectrophotometric method was preferred to determine the total phenols with the Folin-Ciocalteu method, the total tannins with polyvinylpolypyrrolidone binding method, condensed tannins with the butanol-HCl method, hydrolyzable tannins by calculation and the protein binding capacity with filter paper assay. The dry plant material was ground, extracted and then further processed to make a spectrophotometric assay. The obtained results are broadly in line with the references from the literature. It can be concluded from the results that the method shows sufficient precision for the intended purpose: to give an idea of the amount of tannins in the animals’ diets so that farmers and/or nutritionist can adapt the diet composition as needed and within possible.

Abstract bachelorproef 2 2015-2016Optimalisation of the total fibrous matter analysis

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Heidestraat 19
9820 Merelbeke


Traineeship supervisor
Geert Janssens
Traineeship supervisor
Donna Vanhauteghem
Traineeship supervisor
Sylvie D'Hooghe
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