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

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)

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 wellbalanced 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 flowthrough 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) 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
The effect of replacing Fish meal with 10% of Groundnut cake… 88 weight.The test for significance was done using Fishers' LSD.At the beginning a sample and at the end of the experiment 5 fingerlings were collected from each of the treatments for proximate carcass composition using the method described in AOAC (1990).Some water quality parameters, temperature, pH, dissolved oxygen and conductivity were taken weekly using standard methods (APHA 1980).

RESULTS AND DISCUSSION
No significant differences were observed in the MIW, MFW, FCR, SGR, GCE, K and PS of H. longifilis fed the varying diets (P>0.05)(Table 2).Diet V was best utilized while diet I had the poorest nutrient utilization values.The scattered graph shoed a highly positively correlated length/weight relationship (r 2 = 0.915).The correlation was significant at 0.05.The correlation coefficient r 2 = 0.838.The equation for the graph was Y = -14.19+ 12.51X.The K ranged from 1.65 for diet IV to 3.76 for diet II.The body condition factor (K) was best for fish fed 30.16% crude protein followed by that fed 50.75% crude protein.The fish fed 40.39% crude protein had the poorest body condition.The proximate analysis shows that the moisture content, protein content, lipid and ash differ significantly (P<0.05)although the crude fibre content did not vary significantly (P>0.05)(Table 3).longifilis, Eyo (1995), 45% and for hybrid H. longifilis , Olufeagba (1999), 45%.The replacement of 10% meal in this diet did not have an outstanding change on the protein requirement of the fish.According to Lim and Dominy (1989) the ability of fish to utilize plant proteins differ among fish species.The inclusion of high levels of plant protein usually results in reduced growth and feed efficiency.
Ten percent inclusion of groundnut cake in this study seems to be favourable in the diet of H. longifilis.
The fish with the poorest growth was fed diet I, although the level of replacement of fish meal in this diet was the same as the fish with the best growth, growth relied highly on the total level of protein.
According to Lim and Dominy (1989), protein requirement of warm water fishes range from 30% to 56%.The crude protein level of diet I falls below this and hence the poor performance.Food conversion ratio and gross conversion efficiency were best with diet V.In each case the FCR and GCE did not vary significantly for fish fed the varying levels of protein.
The FCR for all treatments were generally high being 6.59:1 for the best.In aquaculture a feed with FCR of 1:1 and 1:2 (Huet 1972) are considered very efficient but in this study none fell within these acceptable ratios.The poor conversion may be attributed to the feeding management, culture system, experimental condition, water management, improper balance of amino acids, high carbohydrates and decrease in palatability or reduction in pellet quality.The poor conversion may also be attributed to the low lysine.
Although methionine and lysine are low in groundnut cake the incorporation of methionine through the premixes may have made up for the low level while lysine remains low.The condition factor in the feeding trials were all greater than 1 indicating that the fish in all the treatments were in good condition and feeding well.The results of the body composition in this experiment showed the moisture content of the fish did not vary significantly from the initial.The protein content of fish fed diets III and VI were lower than the initial.The fish fed diet I had the highest protein content followed by the fish fed diet V.The fish fed diet III had the highest lipid content while fish fed diet V had the least which was not different from the initial.The ash content of the fish fed varying diets was higher than the initial.The crude fibre content was high with fish fed diet II which was not different from the initial.The fish fed diet IV had the highest percentage survival while that fed diet II had the lowest percentage survival.There was no significant difference in the survival of the fish in all treatments.The mortalities experienced in the experiment may not be diet related as the fish with the poorest growth and that with the best growth had survival rates that are not significantly different from one another.The results of this study show that 10% replacement of fish meal in H. longifilis diet can be efficiently utilized for production of the fish.The palatability, the binding property for good pelleting quality and the non availability of anti-nutritional factor in groundnut cake gives it an advantage over other plant proteins for fish food formulation.

Table 1 :
Proximate composition of the formulated diet

Table 2 :
Growth performance, Food conversion and Survival of H. longifilis for 84 days

Table 3 :
Proximate body composition of H. longifilis fed varying levels of protein