Nutritional evaluation of fermented palm kernel cake using red tilapia

The use of palm kernel cake (PKC) and other plant residues in fish feeding especially under extensive aquaculture have been in practice for a long time. On the other hand, the use of microbial-based feedstuff is increasing. In this study, the performance of red tilapia raised on Trichoderma longibrachiatum fermented PKC (TL-PKC) was evaluated. Seven isonitrogenous and isocaloric diets were formulated. Reference diet, D1 had no PKC, while the other diets, D2 to D5 contained 10, 20, 30 and 40% fermented PKC (TL-PKC), respectively. All diets contained 1% chromic oxide as an inert marker. Red tilapias of average weight of 2.5 g were fed on these six diets for a period of 8 weeks. The fish were fed at 4% of their body weight, twice a day. There was no difference in mortality rate of fish on the various diets used. However, weight gain decreased with an increase of TL-PKC in diets. There were significant (P £ 0.05) differences in the apparent digestibility coefficient (ADC) of protein and dry matter between the reference diet and diet containing TL-PKC. The ADC of both protein and dry matter generally decrease when the percentage TL-PKC was increased in the test diets. There was also no significant difference in carcass protein content among fish on the various diets. However, there was a significant (P £ 0.05) increase in the levels of phosphorus, calcium and copper in the carcass of fish raised on TL-PKC, but the level of lipids was significantly reduced. Decreasing dry matter and protein digestibility with corresponding weight reduction may have resulted from increased crude fibre content of diets with TL-PKC