Introduction
In Zambia, many small scale farmers have been using organic manure and supplementary feed in their ponds to increase productivity. Equally, as reported by
Lovell( 1998), not so many farmers were practicing aquaculture on commercial basis and only few companies were producing nutritionally balanced feed for a few commercial farmers that were operating in the country (
Lovell, 1998). Whether you are raising fish for commercial sale or simply have a pond in your backyard, proper nutrition plays a vital role in maintaining the health of your fish and faster growth (
Hafedh, 1999). However, fish differed in their feed diets and nutritional requirements and it was very difficult to know the actual nutrition requirement for a specific species as it may respond differently to a particular feed; which may affect its growth and survival (
Thomas, 2010). Feed in any aquaculture enterprise operating at semi-intensive or intensive level got the highest share of budget (
De Silva, 1995) and for that reason, feed that gave maximum growth rate together with high survival rate of the cultured species were of interest to many nutritionist in the field of aquaculture (
De Silva, 1995). Fish diets are formulated by nutritionists to ensure they receive the nourishment they need for best growth and feed conversion (FCR’s) (
Hafedh, 1999).
Zambia has currently more than four fish feed manufacturing firms, which are responsible for producing quality fish feeds. Despite these feeds being readily available, many small scale fish farmers in most instances were unable to purchase them due to high prices, thus a need to come up with cost effective and nutritionally balanced on-farm aqua feed.
Materials and Methods
The study on growth and survival rate of
O. niloticus was determined from three different feeds that were used. In this study, an on-farm made aquafeed (Diet 1) from National Aquaculture Research and Development Centre (NARDC), two commercially produced aqua feeds, namely: Namfeed (Diet 2) and Tiger Animal Feed (Diet 3) were administered to
Oreochromis niloticus, a native species to central and North Africa and the Middle East (
Boyd, 2004), in order to ascertain which feed was best for their survival and growth. According to FAO ,
O. niloticus was considered a good candidate for aquaculture because it grew faster to good market size, especially the male fish. This species was popular amongst most small scale and commercial farmers in Zambia. However, despite being a good species for aquaculture,
O. niloticus was withdrawn from small scale aquaculture in Zambia (
Simataa and Musuka, 2012).
Since the experiment was conducted in experimental ponds made of concrete sides, growth and survival rate of the fish was expected to be influenced by feed fed only, not from natural sources. The feed was also expected to increase growth and survival rate of the fish since they were all nutritionally balanced feeds.
Study site
The study was carried out in 2m × 4m Hapas mounted in a 30m × 50m pond at the National aquaculture research and development centre (NARDC) in Kitwe for twelve (12) weeks to allow for more data to be collected to ascertain whether there were any statistical differences among the different feeds.
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Figure 1 Showing the study area (Source: NARDC)
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Experimental setup and design
This experiment was a single factor in a completely randomized design (CRD), with three treatments. A total of 90 O. niloticus fingerlings with a stocking rate of 15 fish (i.e. with an average initial body weight of 10.5 ± 0.57g and length of 35.5cm/fish) per hapa were used, replicated two times. The fingerlings’ were sourced from an earthen pond within the farm and acclimatized in a tank for two weeks. Thereafter, fingerlings were randomly selected from the acclimatization tank, weighed and measured before stocking in hapas. Prior to the commencement of the experiment, fish was conditioned to the rearing environment for 48hrs without feeding.
Water source and water quality
The source of water for NARDC fish farm was Mwekera Dam, which was readily available throughout the year (perennial). Water in the experimental pond was maintained at constant level with the same condition throughout the period. Water quality parameters such as: dissolved oxygen, pH and temperature were measured twice per week using a Diometer kit to maintain a stable environmental condition.
On-farm aquafeed (Diet 1) formulation
The ingredients of the diet, which were purchased from the markets within Kitwe, comprised: fish meal, soybean meal, maize bran, vegetable oil, vitamin and mineral premixes, while cassava meal was used as binder. Fish and soybean meals being major protein sources in fish and shell-fish diets, were proportionally included as required (
Olvera – Novoa et al., 1990;
Refstic et al., 1999).
The diet with 30% crude protein (CP) was formulated, using Pearson’s square method to contain essential nutrients to meet the nutritional needs of the fish as required in any culture system to improve growth rate with higher protein content as described by
Barrows and Hardy (2001).
Diet preparation
On-farm aqua feed was prepared following the procedure outlined by
Lovell (1998). It was prepared by first mixing the dry macro-ingredients; of fish meal, soybean meal, rice bran and maize bran, before adding oil. Vegetable oil was included in the diets at 1% for all diets to provide n-6 fatty acids (
Lovell, 1998). Micro-ingredients, mineral and vitamin premixes were added each at 1.5% to the macro ingredients and thoroughly mixed. Lysine and DCP inclusion rate was at 100g each. Cassava meal was used as a binder at 2% inclusion rate to improve stability in water, increase pellet firmness, and reduce the amount of fines produced during processing and handling as recommended by NRC.
Pellet making and storage
The process was done by adding 450ml water per kg of diet and stirring the mixture to form dough that had a stiff, plastic consistency when compressed, appropriate for pelleting. The dough was passed through a 3mm mincer and pellets were air dried indoors away from direct sunlight until firm to the touch. Dry pellets were broken into suitable size and stored in a well-ventilated room.
Meanwhile, Diets 1 and 2 sold in 50Kg bags were bought from the stockiest called Border farmers’ cooperative in Kitwe.
Feeding the fish
Experimental diets of 30% crude protein were presented to fish in form of pellets. Each calculated ration was divided into two equal portions which were fed at 9:00 and 15:00 hours. Daily feeding rate was at 5% of fish mean body weight per hapa. However,
Stickney and Kohler (1990) observed that healthy, rapidly growing fingerlings usually eat 3-4% of their body weight daily in dry feed.
Sampling and Data Collection
Fish measurements
The growth of fish was monitored through fortnight sampling. Body weights and lengths for all fish from each hapa were recorded. Precautions were taken to minimize stress during the weighing process by anaesthetizing the fish with clove. Standard length, total lengths (TL) as well as wet weight (Wt) of each fish was recorded. A graduated measuring board was used for length (cm) measurement of fish (
Goddard, 1996), and digital scale was used. At the termination of the study, fish were harvested, weighed and measured individually to obtain a final mean body weight and length. Precautions were taken to minimize stress during the weighing process by anaesthetizing the fish with Clove, a food spice. Various procedures were used to assess survival, growth, feed utilization, feed intake, and condition factor (K) and weight gains of
Oreochromis niloticus.
Survival rate of fish
Survival was also determined. Every dead fish was recorded to determine survival rate.
Data collection
Data was collected on a number of parameters. Some of the formulae used to determine the various data parameters are outlined as follows:
a) Specific Growth rate (SGR); this was calculated from the formula adopted from
Begum et al.(2005);
SGR=
b) Percentage Increase in Weight: as proposed by
De Silva and Anderson (1995), this was calculated as follows; %IWG= (Wf-Wt)/Wt*100.
c) Percentage Survival Rate (%SR) = (Total number of Fish – Total number of Dead fish/Total number of Fish) × 100.
d) Feed conversion ratio (FCR) was calculated by dividing the dry weight of feed offered in a given period of time by the wet weight gained (g). FCR = Total dry feed offered (g)/Total live weight gained by fish (g) (
Wee and Shu, 1989;
Stickney, 1994).
e) Condition factor (K), an expression of the relationship between fish length and weight was calculated from: K = [100 x W/L (cm)
3], where: W is weight in grams and L is length in centimetres (
Barnabe, 1994).
In order to keep up to date with the world of information, secondary data from published literature, which included: journals, research papers from libraries, the internet and government reports were used to compare collected data with documented information.
Data analysis
Data on growth performance, feed intake, feed utilization, survival, condition factor and whole body composition were recorded for subsequent analyses. The data were entered into Microsoft Excel spreadsheet before exporting it to SPSS 12.0 for analysis, specifically comparing the means, considering that all P-values less than 0.05 indicated significant differences (
De Silva et al., 1995). All the data was checked for assumptions of analysis of variance. Data that did not meet normality distribution were transformed as described by
Pallant (2001). Mean values of final fish weight, specific growth rate and survival parameters were compared using one-way analysis of variance (ANOVA).
Results and Discussion
Growth performance
Figure 2 shows the weekly growth trend of the experimental fish fed three treatment diets for twelve (12) weeks.
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Figure 2 Growth in rate of Oreochromis niloticus raised in hapas over 12 weeks
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Although, growth of the fish continued to improve over time, fish fed on Diet 1 did not show remarkable improvement, despite being formulated with 30% crude protein. The two treatments (Diets 1 and 2) fed on Oreochromis niloticus, however, yielded less successful results, compared to Diet 3. Diet cannot be ruled out completely as not giving good results. Greater consumption of small pellets than large ones could have influence on the growth size of fish. Small pellet might have been relatively easier to eat compared to large sized ones. In the present study, there was minimum difference between Diets 2 and 1 at 30% CP. Omoregie and Ogbemudia (1993) reported that Oreochromis niloticus requires percentage crude protein range of 30-35%, although an earlier study by Faturoti and Akinbote (1986), indicated that Oreochromis niloticus requires 28% for fry and fingerlings respectively.
Overall,
Figure 3 shows that Diet 3 recorded the highest growth rate over twelve weeks experimental period, while the least was from Diet 1.
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Figure 3 Percentage growth of fish under experimentation for twelve (12) weeks
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The inability of fish fed on Diet 1 to catch up in body weight with others may not wholly be known. Poor performance of Diet 1 could therefore, be attributed partly to particle size and quality of ingredients. However, no significant growth performance difference was observed on the fish fed Diets 1 and 2 (p> 0.05), whereas those fed on Diet 3, a significant difference was noted at P<0.05. According to Wolhfarth and Moav (1993), a significant relation existed between the initial weights and growth parameters of most fish. Figure 4 shows the mean standard length of fish under experimentation. However, Diet 1 has demonstrated that once it was improved upon it could perform better.
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Figure 4 Mean standard length of fish under experimentation for twelve weeks
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The trend was the same with mean standard lengths of the fish. The average total body length was 90.2 cm for fish fed Diet 1, 106.1 cm for Diet 2 and 114.8cm for Diet 3. Based on this, it was quiet clear that Diet 3 performed far much better than the other two.
Mean weight gain and survival rate
The growth performance of the fish in terms of mean weight gain, percentage weight gain (PWG), specific growth rate (SGR), Feed conversion ratio (FCR) and survival rate is presented in
Table 1.
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Table 1 Fish growth over a period of twelve week
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The best growth was recorded for groups of fish fed on Diet 3. Final mean body weight ranged between 21.6g, Diet 1, 22.9g in Diet 2 and 29.2g in Diet 3, which was by far the highest. Feeding the fish with Diet 3 resulted in significantly higher mean fish weight than that of fish fed on Diet 2 and 1. Similarly, highest mean weight gain (MWG) and percent weight gain (PWG) were recorded in fish fed Diet 3. This result was in agreement with the findings of Kestemont (1995), who reported that in aquaculture; initial stocking size is an important factor affecting the culture period, feed conversion, and final weight. In general survival rate of the fish in all treatments was excellent. Fish fed on Diet 3 performed very well with 93%, while those fed on Diet 1, recorded a slightly higher mortality rate and reasons for that were unknown, despite most of the other factors being normal.
Water quality parameters
Table 2 shows weekly water quality parameters.
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Table 2 Mean 12 weekly values of water quality parameters
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Results obtained show that means values of water quality parameters over twelve (12) weeks experimental period, were within the acceptable range for freshwater fish according to Abd Abd El-Hakim et al.(2002) and Abd El-Hamid (2003). In the three hapas treatments average water temperature of the different treatments ranged between 23.9 and 26.1℃. The concentration of dissolved oxygen (mg/L) ranged between 3.66 mg/l and 7.29 mg/L. Kamal et al.(2004) reported that levels of dissolved oxygen above 4 ppm is considered a limiting value, below which, fish may live but cannot feed or grow well. Meanwhile, the average pH values for the treatments ranged from 7.18 to 7.60.
Conclusion
It could be concluded that the growth performance and survival rate of Oreochromis niloticus fed with 30% crude protein, was observed to be higher in fish feed on Diet 3, which showed significantly difference of (p<0.05) compared to Diets 2 and 1. However, there was no significant growth difference (p>0.05) between Diet 2 and 1 In the same vein fish fed on Diet 3 had high survival rate compared to those fed on Diets 1 and 2. Diet 1 performed very poorly in comparison with the two commercial feeds. However, Diet 1 can be improved upon significantly to become cost effective and nutritionally through further research.
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