Use of Oyster Processing Byproduct to Replace Fish Meal and Minerals in the Diet of Nile Tilapia Oreochromis niloticus Fry

A byproduct from processing oysters (Crassostrea iridalei) for human consumption was evaluated as a possible protein source to replace fishmeal in the Nile tilapia diet. In an 8 week-feeding trial, fish were fed 7 experimental diets containing various inclusion levels of oyster byproduct (OBP) which replaced fish meal. Diet 1 contained 0% OBP, while Diets 2-6 contained 5%, 10%, 15%, 20%, 25% OBP respectively; Diet 7 was a fishmeal-based diet with OBP as the only source of dietary minerals. The optimum amount of OBP inclusion levels producing maximal responses i.e. final average body weight (FABW), weight gain (WG), specific growth rate (SGR), food conversion rate (FCR) and protein efficiency rate (PER) was estimated using the Broken Line Model of analysis. Average optimum level was 17.0% of dietary OBP (fishmeal replacement of 63.8%). Diet 4 (15% OBP=56.4% fishmeal replacement) resulted in statistically similar growth and feed efficiency parameters to Diets 1-3 and were closest to the estimated optimum inclusion level. Total mineral replacement by OBP (Diet 7) resulted in differing results; SGR values were statistically similar to those of the other dietary treatments; however FABW was inferior, and values for WG, FCR and PER were intermediate. In conclusion, OBP could replace as much as 63.8% by weight of dietary fishmeal and probably a large proportion of the mineral mix in the diet of Nile tilapia fry.