Use of coffee pulp as feed ingredient for tilapia culture

This research focused on the feasibility of using coffee pulp (CoP) in diets for tilapia ( Oreochromis aureus ). First, a literature survey analyzed the limitations of CoP as an animal foodstuff (several antinutritional factors: ANF's, and high fibre contents), different ways to upgrade the CoP nutritional value and the maximal inclusion level of CoP in diets for ruminants, monogastric animals and fish ( Chapter 1 ).Next, an inventory of agricultural activities in the country (Costa Rica) was realized for one production year (1993-94). The most important agricultural activities were identified and classified in two categories: crop and animal husbandry sectors. Residues (wastes and by-products) of both sectors were characterized by their seasonality, their amounts produced, methods of treating wastes, their use (if any) and their potential pollution risk. In addition, most relevant wastes were more precisely studied and, their chemical composition and the presence of potential ANF's indicated. The CoP was selected for further study because of its annual production and its potential pollution risk. Changes of the chemical composition of CoP during the harvesting season and using different drying methods were examined in more detail ( Chapter 2 ). Limitations to use CoP as a foodstuff for fish were studied and the possible causes of differences on growth responses to CoP diets found in tilapia reared either in extensive and intensive systems (pens in ponds and recirculation-aquaria system) are mentioned ( Chapter 3 ).As several ANF's were identified in CoP, the critical value of some of them was determined for Oreochromis aureus fingerlings. Based on the growth and feed efficiency (digestibility), the following dietary critical levels of fibre and tannins were determined: 4.4 g kg -1of tannins and 106.5 g kg -1of fibre. Dietary caffeine levels increasing from 2.4 to 4.6 g kg -1tended to reduce fish growth, feed intake and also nutrient digestibility of O. aureus ( Chapter 4 ).Chemical treatments have been applied to straws and coffee hulls with positive results. Uses of some of these treatments were tested in fresh CoP. The NaOH, the combined HCl-NaOH and NaOH-ensilage treatments were applied to CoP to reduce the content of caffeine, total phenols (polyphenols), tannins and cellulose. Biological treatments were also used to diminish ANF's in CoP but they also may increase CoP protein and fat contents. The ensilage of CoP with molasses was also tested at higher concentration (100 g kg -1) than normally done; however, it did not result in any additive effect. Microbial decomposition was done in a closed lab controlling parameters such as environmental moisture and temperature, photoperiod and temperature of CoP samples. Specific cellulolytic bacteria were used to degrade fibrous components and ANF's of CoP. The inoculation of CoP was done with a cocktail of five species of Bacillus for 28 days under aerobic conditions. The best result in relation with the upgrading of the nutritional quality of CoP was found with the bacterial treatment ( Chapter 5 ).Subsequently, CoP treated with Bacillusssp. was included in diets for tilapia. The final product was included at different concentrations (0, 60, 120, 180 and 240 g kg -1) in the fish diets and fed to O. aureus fingerlings for 4 weeks. At the end of the experimental period, the fish response was evaluated in terms of growth, feed intake, protein utilization and nutrient digestibility ( Chapter 6 ). Best results were found with diets containing 0 and 60 g kg -1CoP. Problems related to the upscaling of the bacterial treatment are mentioned and discussed.The overall results are integrated in one general discussion and several conclusions and recommendations are drawn to upgrade coffee residues for animal feeding purposes ( Chapter 7 ). The potential of using CoP in diets for tilapia cultured in extensive or semi-intensive systems is discussed. Technological and engineering aspects impaired the upscaling of the bacterial treatment for CoP and produced a final product with a lower quality than the one obtained at laboratory scale.