Digestibility, Growth And Economic Performance Of Nile Tilapia (Oreochromis Niloticus) Fed On A Mixture Of Plant Protein Diets In Cages.

ABSTRACT

Fish feed is one of the critical components in aquaculture production and accounts for

over 60% of total operational costs with protein component being the most expensive

ingredient. Traditionally, fishmeal (FM) has been the primary dietary animal protein

source. However, with dwindling capture fisheries, FM has become increasingly

scarce and expensive due to its demand from human consumers and livestock feed

manufacturers. This in turn makes the cost of fish feeds expensive leading to low

profit margins in farmed fish. Therefore, there is need to identify alternative, low cost,

and nutritionally balanced sources of protein for the growth of the industry. Although

plant-based protein sources are viable alternative in replacing FM, there have been no

studies on mixture of plant proteins to establish their economic utility in fish farming.

This study evaluated the effects of replacing freshwater shrimp (caridina nilotica)

meal (FSM), with varying levels of soybean (Glycine max) meal (SBM), cottonseed

(Gossypium spp) meal (CSM) and sunflower (Helianthus annuus) meal (SFM) on

growth performance, digestibility, whole body composition and economic returns in

diets of Nile tilapia (Oreochromis niloticus). Fingerlings averaging 25g in body

weight were stocked in net cages installed in three 800m2 fertilized earthen ponds.

Each pond had 15 cages evaluating five diets with three replicates for a culture period

of six months. Three experimental set ups were designed to evaluate the efficiency of

a combination of SBM with other plant protein sources in replacing FSM in fish diets.

In trial 1, five isonitrogenous (30% CP) and isocaloric (3.5 kcal g-1) diets were

formulated, substituting Fresh water shrimp meal with Soybean meal at rates of 0, 25,

50, 75 and 100%.Trial 2 similar diets as above were formulated replacing fresh water

shrimp meal with a combination of SBM, CSM and SFM at rates 0, 25, 50, 75 and

100%. In Trial 3, similar diets as in experiment 2 were formulated replacing FM with

a combination of CSM and SFM at rates 0, 25, 50, 75 and 100%. All fish were fed

twice daily at 10% of their body weight. Data were expressed as means and standard

error of the mean. Growth and proximate composition were analyzed using one-way

ANOVA at p< 0.05, and differences among treatment means identified using Tukeys

Multiple Range Test. Results from the study in trial 1, showed that fish fed on D0 had

higher final weight (p