ABSTRACT
Alternative plant protein sources are generally cheaper compared to animal protein sources and may be the solution to reduce the high dependence of farmers on fish meal due to the limited world supplies and increasing price of fishmeal. This study focuses on growth performance of Nile Tilapia (Oreochromisniloticus); its gastric evacuation rate and carcass composition when fed with fresh aquatic plant and artificial diet.
Azollapinnataand artificial diet (control) were fed at 3% body weight of 90 Oreochromisniloticusweighing 24±1.43g for 56 days (8 weeks) in three treatments T1(artificial diet), T2 (artificial diet 50% and aquatic plant 50%) and T3 (aquatic plant); each having three replicates. Specific Growth Rate (SGR), Food Conversion Ratio (FCR), Protein Efficiency Ratio (PER), Mean Weight Gain (MWG), Protein Intake (PI) and Length-Weight Relationship were used to determine the growth performance and feed utilization. The serial slaughter method was used to determine Gastric Evacuation Rate (GER) and Gastric Transit Time (GTT). Proximate composition of fish carcass was determined using standard methods. Data were analysed using Descriptive analysis and ANOVA at α0.05.
Fish fed both artificial diet and aquatic plant T2 attained a significantly higher MGW and SGR, and attained the best correlation coefficient value which indicates a good relationship between length and weight. T1 and T2 showed no significant difference in FCR but were significantly lower than T3. The PER showed that T2 was significantly higher than T1 and T3. Duncan’s test of significance indicated that there was no significant difference in the daily feeding rate and GER of Oreocromisniloticusacross the treatments but GTT differed in T3. Fish fed only Azolla, T3 had a GTT of 3 hours where as T1 and T2 was 4 hours. Carcass proximate analysis showed that crude protein of T3 was significantly higher than T1. Fat content of T3 was significantly higher than those of T1 and T2.
Oreohchromisniloticusperformed better when fed with both artificial diet and aquatic plant, it also attained a higher crude protein level and lower moisture content when fed only aquatic plant compared to those fed only artificial diet.
Key words: Oreohchromisniloticus, utlilization of aquatic plant, growth performance, gastric evacuation, carcass composition
CHAPTER ONE
1.0 INTRODUCTION
1.1 Tilapia culture in Aquaculture
Food is a basic necessity of life, second only to air and water. The global food equation recognizes two major components namely; food crop component and animal protein component. Animal protein source include fish, poultry and livestock. Fish consumption in Nigeria is higher due to its comparatively cheaper price compared to protein from other livestock (Okonjiet al., 2013). Available fish for consumption comes from aquaculture and capture fisheries with the capture fisheries becoming less sustainable. Aquaculture is the husbandry of aquatic food organisms (mostly fishes). It involves breeding new fish stock, holding them in captivity and feeding them (Agbebi and Fagbenro, 2006), and it is believed to be a more sustainable source than capture fisheries. Report from the Food and Agriculture Organization (FAO) stated that Nigeria aquaculture industry produced over 30, 000 tonnes of fish in the year 2000; mostly tilapia (14,388 tonnes) cultivated under intensive and semi-intensive production system. Despite this status, the yield from aquaculture is below optimum when compared with its potential, considering both ecological and socio-economic environment (Fagbenroet al., 2004) because fish culture (mostly tilapia) in Nigeria is predominantly an extensive land-base (earthen pond) system practiced at subsistence level.Tilapias belong to the cichlid family and one of the most productive and internationally traded food fish in the world asproduction of farmed tilapia is among the fastest expanding food sectors in the world (Adams et al., 2014). They are widely cultured in about 100 countries in the tropical and subtropical regions. According to Fagbenroet al., 2011, Nigeria is the second largest producer of farm-raised tilapias in Africa, after Egypt. He also reported that Tilapia culture in Nigeria remained largely a subsistence level activity until 2000, when it began to expand rapidly following the successful commercial farming of catfishes during the last decade (Afolabiet al., 2007; Alfred andFagbenro, 2006). There are over 25 species of tilapias in Nigeria, out of which about six species are used for aquaculture, namely, Tilapiazillii,T. guineensis (generally herbivores,substrate spawners), Sarotherodongalilaeus,S. melanotheron(bi-parental mouth-brooders,planktophagous), Oreochromisniloticus and O. aureus (maternal mouth-brooders, omnivorous).According to Adams et al.,2014,there are basically three systems of culturing tilapia: extensive, semi-intensive and intensive systems.
Mohanty (2004) as cited by Opiyoet al.,2014, reported that in many countries where fish farming is conducted at semi- intensive culture level, more than90% of farmers use on-farm made feeds in order to reduce production cost. The use of nutritionally balanced feeds constitute an unwise use of resources and economically unsoundpractices in semi-intensive aquaculture where external feedinput is expected to supplement natural food production.
Opiyoet al,.2014 reported that development and management of fish feed play avital role in aquaculture growth and expansion. In fact, it is amajor factor that determines the profitability of aquacultureventures.
1.2 Fresh Aquatic Plants as Plant Based Protein
The use of fresh plants as fish feeds has been investigated by several researchers. When fed only on fresh plants in closed systems, growth performance is usually poor; Setlikova and Adamek (2004) reported slow growth of O. niloticus fed Potamogetonpectinatus and Elodeacanadensis and negative growth when offered Spirodelapolyrhiza and Myriophyllumspectrum. In another study, Okeyo and Montgomery (1992) reported negative growth in O. aureus when fed three aquatic macrophytes (Elodeacanadensis, Myriophylumspicatum and Potamogetongramineous). However, improved growth performance was reported by Chowdhuryet al., (2008) in pond reared Oreochromisniloticus when supplemented with duckweed. Similarly, favourable growth rates were reported when T. rendalli was fed Napier grass (Pennisetumpurpureum) (Chikafumbwa, 1996).
1.3 Problem statement
Despite that tilapias require the 10 essential amino acids- EAA (arginine, lysine, histidine,threonine, valine, leucine, isoleucine, methionine, phenylalanine and tryptophan), specific EAArequirements of most farmed tilapias have not been determined. Few studies have consideredEAA requirements of Nile tilapia, Oreochromisniloticus and 0. Mossambicus(El-Sayed, 2004). Traditionally, fishmeal has been used as the major protein source in fish feeds because of its nutritional value and palatability (Nguyen et. al., 2009). Due to the limited world supplies and increasing price of fishmeal, the majority of research on fishmeal replacement with alternative proteins in fish diets has focused on the use of protein derived from plant sources (Enami, 2011).
1.4 Justification of Study
Alternative plant protein sources are generally cheaper compared to animal protein sources. High protein levels are a prerequisite in selecting alternative plant sources, as dietary protein affects the growth performance in tilapia (Musukaet al.,2009). The study would help to know how Azollapinnatais rich in proteins and essential amino acids. This would educate Fish Farmers on how to be more cost effective in production and enhance profit maximization.
1.5 Objectives of Study
The objectives of this study are to;
1. Determine the effects of fresh aquatic plant (Azollapinnata) and artificial diet on growth performance of Nile Tilapia (Oreochromisniloticus);
2. Evaluate the gastric evacuation rate and carcass composition of Nile Tilapia (Oreochromisniloticus) fed with aquatic plant (Azollapinnata) and artificial diet.
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