Substitution of fishmeal with solid state fermented African yam beans (Sphenostylis stenocarpa) in novel Nile Tilapia diets

Abstract

Legumes are proteinous and plausible fishmeal alternative in aquafeed production. A major disadvantage of legumes is the presence of some antinutritional factors (ANF) and low content of some essential amino acids like lysine and methionine. Solid-state fermentation can remove ANF and increase the nutritional value of legumes. The African yam beans, Sphenostylis stenocarpa is a neglected proteionous legume that is vastly cultivated all over Africa and Asia. In the present study, solid-state fermented African yam beans (FAYB) was used in substituting fishmeal (FM) in five isonitrogenous and isoenergetic feeds, labeled as Feeds 1 to 5. The combination levels (FM : FAYB) were as follows: Feed 1, 400:0, Feed 2, 300:100, Feed 3,200:200, Feed 4, 100:300 and Feed 5, 0:400. A total of 270 Nile tilapia fingerlings, with an average weight of 22.64g, were stocked at 15 fish per 20 liters aquarium at three replicates per treatment. Culture water parameters were monitored. The fish were fed ad libitum three times daily for 30 days. Growth, nutritional and biochemical parameters were analyzed using standard procedure. Results revealed that tilapia fed Feed 3 had the best specific growth rate (SGR) of 3.38±0.05 %/day. This was followed by those that received Feed 4, having SGR of 2.74±0.11 %/day. There was no significant difference (p > 0.05) in SGR of fish fed Feeds 1 and 5. The results of food conversion ratio (FCR) followed similar trend as SGR. Quadratic regression analysis of growth indices against protein efficiency ratio indicated linear relationship. The best values for haemato-biochemical parameters of the tilapia were shown in Feed 3. Low values of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were obtained in this study. This may denote that the diets were not deleterious to the gut health of the fish. Total cholesterol increased as the inclusion level of FAYB increased. Inference from the study suggests that Feed 3 (diet with equal proportion of FM and FAYB) gave the best fish performance.