Background

Aquaculture is getting worldwide interest due to continuous diminishing of harvests from capture fisheries and roused by mounting prices for quality seafood. In the last several decades, aquaculture production has continued to grow exponentially. Aquaculture production increased from 5.3% in 1970 to 32.3% in 2000 as a percentage of total fisheries landings (FAO, 2002). It has upheld an average annual growth rate 8.9% since 1970 compared with growth rates of terrestrial farmed meat production systems (2.8%) and capture fisheries (1.4%) (FAO, 2002). China, Japan, South Korea, and the Philippines are the leading producer of aquaculture goods in Asia (Hanfman, 1989). Meeting protein demand, feeding increasing population and employment generation are the prime task of aquaculture (Naylor et al., 2000).

After carps and salmonids, Pangus is the most important cultured fish group in the world because of their rapid growth, tolerance to high stocking densities and poor water quality, high reproductive rates and susceptibility to diseases (Stickney, 1986; Chamberlain, 1993). Naturally it is herbivore species that accustomed to eat plant ingredients (Stickney, 1986; Chamberlain, 1993). It may be grown in open ponds, cages, aquariums, tanks and raceways etc.

Bangladesh is blessed with diverse fisheries resources found in rivers, canals, lakes, beels, ponds, estuaries covering area of about 4.34 million hectare (DoF, 2003). Rivers, floodplains, lakes, reservoirs and ponds cover an area of 4.05 million hectare while fresh water ponds cover an area of 0.15 million hectare (0.15 million ha.) and coastal shrimp farms cover an area of 0.14 million hectare (DoF, 2003). According to the Bangladesh Bureau of Statistics (BBS), the fisheries sector, including aquaculture and capture fisheries, has had an annual growth exceeding 7% since 1995 and contributed 6% to the country’s GDP in 2000 (BBS, 2000a). Fresh water aquaculture led this with an annual growth exceeding 10% over the last decade with annual fish consumption of about 14 kg/person in 2000 (BBS, 2000b).

The success of fish culture largely depend on supplemented feed. Cost effective formulation along with essential nutrient manufactured feed needed for normal growth and development (Halver, 1976). Nutrient rich feed is the important factor for the culture system since it contains 60-70% of the total process cost. Today, the growth of aquaculture has led to a dependency on artificial feed ingredients. In this circumstance, low cost feed has become vital for commercial aquaculture venture. To decrease the cost of fish feed ingredients alternative low cost raw materials needed in feed production. These less orthodox feed components are often ideal for manufacturing farm-based aqua feeds (Akiyama and Hunter, 2000; Tacon and Foster, 2000). Several researches were conducted on the effectiveness of handmade feed on growth performance of Thai pangus. But this is the preliminary study to measure the efficiency of the home made feed on Thai pangus growth at Durgapur in Comilla.

1 Materials and Methods

1.1 Study area

The present research was carried out at Durgapur in Comilla (Figure 1). The total land area was about 2 acres. The ponds were well constructed and 3×3 (3 pond for each treatment) culture ponds were used for this experiment. The ponds were rectangular in shape with mostly plain bottom features.

1.2 Pond preparation

1.2.1 Drying the pond

First of all, water of the pond was pumped out and the level of water was abridged up to a depth of 1 feet. Rotenone was used to kill fishes and other faunas (6 kg/acre). Netting was done after one hour of rotenone application to collect dead fishes. Then all ponds were kept sun-dried until the soil fractured. Ponds were tilled entirely after sun drying to a depth of 5-10 cm for two times. Finally reconditioning of pond bottom trench, leveling and repairing were done.

1.2.2 Liming

CaCO₃ was used as liming agent to maintain the soil pH. The lime requirement was determined by using the table of Boyd’s (1982). Lime was first crumpled into dust and disseminated all over the ponds bottom and dikes. Soil pH measured regularly by pH meter.

1.2.3 Water filling and fertilization

The pond was watered by deep tube-well. Water depth was maintained at 15 cm for 4 days and progressively raised up to 1.2 m. Organic fertilizer was applied at a rate of 3 ton/ha, and inorganic fertilizers were used at a rate of 100 kg/ha. After raising the soil pH at a desired level (7.5-8.3), the ponds were treated by lime (CaCO₃) at a rate of 125 kg/ha to soothe the soil pH as well as to support the fertility of the ponds.

1.3 Stocking of fish

The small fish having 125-175 g, collected from grow out pond and 22,000 pcs pangus per hectare was stocked in the morning.

1.4 Feeding

1.4.1 Diet preparation

Ingredients selection: Oil cake, meat and bone meal, soybean meal, fish meal, rice polish, wheat flour, corn powder, de oiled rice-bran (DORB), vitamin premix and water was selected for hand-made feed formulation. Feed formulation was completed by using simple technique machine normally used by farmers.

Grinding: Grinding was executed to decrease the particle size which increases the feed digestibility, acceptability, palatability and rise the bulk density of some ingredients. It also increases the pellet quality by reducing air space between particles and allow closer surface to surface contact for given volume of feed.

Sieving: Sieving was done to make particles in same size and to eliminate greater particles.

Weighing: Weighing of ingredients was done by using solver package program.

Mixing: Mixing was done until uniformity of the feed ingredients was observed.

Conditioning: Conditioning was done to make the feed particles flexible by autoclave where water was provided in the form of steam. The high temperature of steam causes some gelatinizing of raw starch present in all vegetative ingredients and providing the necessary adhesion to form pellets.

Pelleting: The renovation of a soft, often dusty feed into a hard pellet was accomplished by compression, extrusion and adhesion with a pellet machine.

Drying: Excess moisture produced from conditioning and pelleting process was removed by keeping feed pellets sun dried and this was done by spreading pellets on a thin layer paper and polythene.

Protein analysis: Protein level of quality feed (D1), rahat feed (D2) and formulated feed (D3) was estimated by Micro Kjeldahl Method developed by Kjeldahl (1883).

1.4.2 Feeding trial

The experiment was conducted completely by randomized design. Three experimental diets D1, D2 and D3 were assigned to three different treatments T1, T2 and T3 respectively each having another three replications.

Experimental feeds were given at a rate of 6% of their body weight/day for the first month, 5% and 4% for 2^nd and 3^rd month respectively. Stock was fed 2 times/day and feed was given through broadcasting. The amount of feed consumed for each pond was calculated.

1.5 Measuring growth performance and feed utilization

Growth performance of pangus was measured in terms of daily weight gain (DWG), and specific growth rate (SGR). Feed utilization was measured in terms of feed conversion ratio (FCR), feed efficiency, and protein efficiency ratio (PER). Survival rate (%) was also calculated.

1.5.1 Sampling

Data on growth, daily weight gain, feed conversion, length and weight were collected monthly. Survival was determined by counting the fish at the day after the last day of treatment. Fish were casually sampled from pond by gill net. Then they were placed into an aerated beaker of water. An electronic balance was used for weight measurement and dead fish were recorded. Initial weight and length of pangus were measured for 25 fish individually and sampling was accomplished at 30 day interval their weight was recorded in nearest grams.

1.5.2 Weight gain

Mean body weight was determined by simple arithmetic calculation as advocated by Sedgwick (1979).

Weight gain = Mean final fish weight – Mean initial fish weight

1.5.3 Specific growth rate (SGR)

The SGR is the instantaneous change of fish calculated as the percentage increase in body weight per day over any given time interval and expressed as (Bagenal, 1978):

1.5.4 Daily weight gain

The daily weight gain is the mean weight gain on daily basis and it is calculated as (Bagenal, 1978):

1.5.5 Feed conversion ratio (FCR)

The FCR is defined as the amount of dry feed per unit live weight gain and was calculated (Castell and Tiews, 1980) as:

1.5.6 Feed efficiency

Feed efficiency is the final yield divided by the input (i.e. the inverse of FCR) (Bagenal, 1978).

1.5.7 Protein efficiency ratio (PER)

PER is defined as the gain in weight of fish per g of crude protein fed and calculated (Castell and Tiews, 1980) as:

1.5.8 Survival rate

The survival rate of pangus for each treatment and replication were estimated on the basis of number of fish harvested at the end of trial period (Bagenal, 1978).

1.6 Data collection and analysis

Data were collected in various stages of the experiment. Different physico-chemical parameters of nursing ponds were recorded. ArcGIS v.10.3 was used to create sampling site of the study area. MS Excel program was used to store all growth data. An economic analysis in terms of feed cost per unit production was made to estimate the cost benefit analysis.

2 Results

In the present study the efficacy of handmade feed on growth performance of Thai pangus (pangasius hypophthalmus) was studied. The concentration of protein was determined in the experimental feed (Table 1).

2.1 Growth performance and feed utilization

2.1.1 Weight gain

Fish growth was positively affected by protein level and at the end of 90 days of culture period, maximum growth was obtained in 24% protein (800 g/ind.) whereas the lowest growth was obtained in 23% protein (750 g/ind.) (Table 2).

2.1.2 Daily weight gain

The highest mean daily weight gain was recorded in 24% protein (7.22 g) and lowest was recorded in 23% protein (6.66 g) during the experimental period (Table 3).

2.1.3 Specific growth rate

The SGR of fish in different treatments was found in between 1.11110769% and 1.1111%. The better SGR for pangus was obtained in 24% and the lower was obtained in 23% (Table 3).

2.1.4 Feed conversion ratio

The mean FCR values of different treatments varied between 1.9727 and 2.0325. The better FCR for pangus was obtained by protein 24% while the poorest FCR was obtained by protein 23% (Table 3).

2.1.5 Feed efficiency (%)

Feed efficiency of different protein levels ranged between 50% and 47.73%. The best feed efficiency (50.59% and 49.2%) for pangus was obtained by 24% and 23% protein diets respectively with insignificant difference (Table 3).

2.1.6 Survival rate (%)

Survival rate was not significantly affected by protein level and at different dietary protein levels was almost similar (98%) (Table 3).

2.2 Economic analysis

An economic analysis in terms of cost per unit production was used to estimate the cost-benefit. The cost of experimental feed was based on the price of ingredients at Durgapur local market in 2016. The cost (Tk/kg) of experimental diets were taka 36.5, 33.5 and 31 for 24%, 23.2% and 23% protein respectively. Highest cost per unit production (72 Tk/kg) is found in 24% protein and lowest (63 Tk/kg) is in diet containing 23% protein (D3) (Table 4; Table 5).

3 Discussion

Culture of pangus species augmented considerably in the last few years because of the stocking density and the optimum protein level. These factors attract the attention of researchers because these features are aim at higher profit without substantial losses in growth ratio and ecological quality. Besides, the growth of pangus depends upon the stocking density, dietary protein quality, energy content of the diet, the physiological status of the fish, age, reproductive state, and the environmental factors such as temperature, salinity, etc. (Lovell, 1989). Dietary protein is always regarded to be of main importance in fish feeding (Jauncey and Ross, 1982). Fish need diets relatively high in protein content because of their poor utilization of carbohydrates as energy source, thus sufficient supply of dietary protein is needed for rapid growth (Lovell, 1989).

The result of the experiment showed that significantly higher growth of Thai pangus 650 g with the highest SGR (1.11110769%/day) was achieved when they were fed with higher crude protein level 24% for adult. Lower growth (600 g) with the lowest SGR (1.1111%/day) was obtained from lower protein level 23% for adult. Huq et al. (2004) found a higher growth (502.77 g) of Thai pangus in monoculture and moderate growth (398.25 g and 383.28 g) in polyculture with carps and prawn using 20% protein diet from a culture period of 7.5 months. Chuapoehuk and Pothisoong (1983) reported that a diet having 25% protein was the best for optimum growth of Thai pangus. Mollah and Sarder (1991) reported that supplemental feeds containing 20-30% crude protein in different combinations gave substantial growth of this species cultured in cages and ponds.

The survival rate of Thai pangus was 98.90-98.82% in all the experimental treatments. The survival rate was about 100% in cemented cisterns reported by Haroon and Hossain (2001). So the survival rate was found not to be influenced by different diets. In T1, T2 and T3 the feed conversion ratio (FCR) were recorded 1.97, 2 and 2.03 respectively. The highest FCR value 2.03 was found in T3 indicates that the hand-made feed D3 was not as good as it could produce high yield. Azimuddin (1998) found the FCR value within 1.73-2.04 in 3 months and Halder and Jahan (2001) found the FCR value within 2.96-3.09 in 5 months. Haroon and Shanta (2001) reported an FCR range of 2.64-3.64 in a culture period of 12 months in cemented cisterns. Ahmed et al. (1996) compared the effect of 3 supplementary feeds on p. pangasius culture feasibility for 3 months in earthen pond, and found the FCR as 5.30, 5.75 and 7.5.

From the above study it was proved that the protein level had great influence on growth performance and highest production. But now protein ingredients are costly and are increasing day by day which has high influence on net profit. Here 24% protein rich diet D1 was bought 6,083 kg, 23.2% protein rich diet D2 was bought 6,000 kg and 23% protein rich diet D3 was bought 5,904 kg biomass having cost of 438,000 Tk, 402,000 Tk, and 372,000 Tk. respectively. Total sells were 547,470 Tk, 540,000 Tk, and 531,360 Tk. So profit for D1, D2 and D3 were 109,470 Tk, 138,000 Tk, and 159,360 Tk, respectively. There were great profit by handmade feed and hence farmers showed interest to use hand-made feed at Durgapur in Comilla.

4 Conclusion

Handmade feed have immense influence on the growth of Thai pangus. Weight and specific growth rate of Thai pangus increased with the increasing of feed protein level. Protein level of diet is the important factor that regulates the profit in aquaculture. The research suggest that the quality and cost efficiency of feed should be given priority to get a commercial growth of Thai pangus.

Authors’ contributions

Mohammad Saydul Islam Sarkar designed and conducted the research and wrote the manuscript. Md. Simul Bhuyan performed data analysis and critical review of the manuscript. Mahmudul Hasan helped in map producing and review of the manuscript.

Acknowledgments

The authors are grateful to all of colleagues for their constructive criticisms and constant help to the successful completion of this research. Authors also expressed their heartiest thanks to the Editor and reviewers for their valuable comments to improve the paper quality.

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