The effect of replacing Fish meal with 10% of Groundnut cake in the diets of H. longifilis on its Growth, Food conversion and Survival

Abstract

Growth, food conversion efficiency and survival of H. longifilis fed diets with varying levels of protein in which 10% of fish meal was replaced with groundnut cake were studied for 84 days. Fish fed the diet containing 44.17% crude protein showed the best weight gain, specific growth rate, food conversion ratio and efficiency. There was no significant difference (P>0.05) in all the growth parameters and the survival rate of the fish. Addition of fishmeal to fish diets increases feed efficiency and growth although it is a very expensive ingredient. In northern Nigeria 1kg of fishmeal costs about five hundred Naira while its equivalent of groundnut cake is about one hundred Naira. Cost-effectiveness of diets could be improved by replacing fishmeal with more economical protein sources such as groundnut cake. @JASEM Feeding in fish farming takes 60% of the operating cost. In formulating suitable nutritive feed for fish, fish meal is the major component. This has made the cost of growing fish over a period of time to be very high. In order to seek for alternative to fish meal suitable plant protein has been investigated over the years (Lim and Dominy 1990; Shiau et al 1990). Fish meal forms the major protein source in fish feed because of its high nutritive value and palatability. Studies have shown that high levels of plant protein in fish diets or complete substitution of animal proteins has resulted in poor growth and feed efficiency in feed (Dabrowski et al 1989; Lim 1992). Poor growth in such studies have been attributed to anti nutritional factors or toxic substances; improper balance of essential nutrients such as amino acids, energy and minerals, high amount of fibre and carbohydrate, decrease in palatability of the feed; and reduction of pellet quality especially water stability (Lim and Dominy 1989). Fish require a well-balanced mixture of essential and non essential amino acids. The most effective, economical source of these amino acids is a proper combination of high quality natural proteins in feedstuffs. A protein that is deficient in one or more essential amino acids is of low biological value while that which closely matches that required by the fish is of high nutritive value (Lim and Dominy 1989). In groundnut cake the sulphur containing amino acids (methionine + cystine) are the most deficient followed by lysine. Groundnut cake is said to be highly palatable and has better binding properties for pelleting than soybeans (Lovell, 1989) According to Jackson et al (1982) groundnut cake can replace 25% of fish meal in the diet of S. mossambicus at higher levels growth rate decreased rapidly. Combining groundnut cake with fish meal which is rich in methionine and lysine will go a long way to produce a highly nutritive feed. This study sets out to investigate the effect of the substitution of fish meal in the diet with 10% of groundnut cake on the growth, food conversion and survival of H. longifilis. MATERIALS AND METHODS Fingerling H. longifilis of mean weight 14.83 ± 0.64g were stocked in 26.4 litre of water in plastic troughs of 25cm in depth and 55cm diameter. The experiment consisted of 18 troughs in a mini-flow through system. Each trough was supplied with an outlet pipe which was covered with a sleeve borne with holes for overflow. A rubber hose of 2mm diameter served as the water inlet pipe. The hose is connected to a tap linked to overhead tank which gets water from a biological sedimentation tank. Water is sprinkled into each trough through tiny holes borne on the hose at every plastic trough. The flow-through was run for 15 hours daily. Sampling was carried out by bulk weighing biweekly. Feeding rates were adjusted after sampling. The flow-through system does not remove all faecal materials and feed remnants and so cleaning was done daily by siphoning. Total exchange of water was done on sampling days. Some water quality parameters were monitored during the period. They include temperature, pH, dissolved oxygen and conductivity. The formulation and proximate composition of experimental diets are shown in Table 1. Feeding was done at 10% body weight twice daily for 84 days. Food conversion ratio (FCR) and Gross conversion efficiency (GCE), Specific growth rate (SGR) and condition factor (K) were derived using the following: FCR = Food Eaten ÷ Weight Gain; GCE = (SGR ÷ Ration) × 100 (Priede and Secombe, 1988); SGR = 100 × (ln Final mean weight-ln initial mean weight) ÷ time (days) K = (W ÷ L 3) × 100 Where W is weight in g and L is length in cm. Statistical analysis was carried out using the computer package of SPSS version 10 to derive the regression coefficient, correlation between length and