Effect of Dietary Carbohydrate Levels and Feeding Frequencies on Growth and Carbohydrate Digestibility by White Shrimp Litopenaeus vannamei Under Laboratory Conditions

Shrimp is the one commodity that contributes significantly to the increase in local revenues in South Sulawesi. In 2006 South Sulawesi shrimp production reached 19414 tonnes and a decline into 16361.4 tonnes in 2007 [1]. Decreased production of tiger shrimp in recent time due to virus attacks WSSV causes the need for diversification of species that are more resistant to disease. Shrimp Litopenaeus vannamei vanamei is one type of penaeid shrimp that have endurance higher than the species of tiger shrimp against viral attack.


Introduction
Shrimp is the one commodity that contributes significantly to the increase in local revenues in South Sulawesi. In 2006 South Sulawesi shrimp production reached 19414 tonnes and a decline into 16361.4 tonnes in 2007 [1]. Decreased production of tiger shrimp in recent time due to virus attacks WSSV causes the need for diversification of species that are more resistant to disease. Shrimp Litopenaeus vannamei vanamei is one type of penaeid shrimp that have endurance higher than the species of tiger shrimp against viral attack.
In a system of intensive shrimp farming in ponds vanamei, feed is one of the strategic components that determine the success of the business. Feed is a very large part of the operational costs in the cultivation of crustaceans [2]. At the event, almost 60-70% of total production costs for the purchase of feed [3,4]. But the last few years of cultivation of these commodities often fail. One of the factors that lead to failure in shrimp farming in Indonesia vanamei cultivation technology is the application that does not comply with the carrying capacity of the waters, the farming technologies among others including feeding technology [5]. The high organic matter derived from the feed that is not consumed and is derived from the metabolism, is one of the triggers declining water quality.
The success of shrimp farming vanamei among others determined by the quality of feed used. To produce optimal growth, feed with shrimp require a fairly high protein content . Optimal growth is achieved when vanamei shrimp shrimp feed with protein content of 40-50% [6]. However, the protein content is too high can lead to decreased water quality cultivation media, which comes from the feed that can not be consumed, faeces and feed protein metabolism.
[7] suggested that the protein needs of the shrimp can be reduced if the energy needs can be met from other sources of non-protein , such as carbohydrates Carbohydrates and lipids are important nutritional components in food shrimp [8]. Increasing the proportion of carbohydrates and not protein feed to meet energy needs can ultimately feed costs. The addition of vegetable protein to reduce the cost of feed has been widely studied [9][10][11][12]. In addition to required as an energy source, shrimp also need carbohydrates for synthesis of chitin. Used by shrimp chitin in the growth process to form and replace eksoskleton during the molting process.
Carbohydrates are a source of cheap energy, but the ability of aquatic organisms, including shrimp to utilize limited. This is due to lack of ability to digest and regulate plasma glucose concentrations. The use of carbohydrate by fish and shrimp are less efficient than land animals [13]. The ability of shrimp in utilizing the limited carbohydrate digestibility due to low [14] and low concentrations of plasma glucose regulation [15]. The low digestibility of carbohydrates associated with the availability of the enzyme α-amylase, whereas low concentrations of plasma glucose regulation allegedly caused by a deficiency of the hormone insulin. Based on the recommendation of the humans who suffer from diabetes, suggested that the feeding frequencyis much more then the ability to utilize carbohydrates can be improved. This is in line with research that the continuous feeding may increase the use of carbohydrates and increase fat reserves through increased lipogenesis process. In addition to the feeding frequencymore frequently, the possibility of higher feed can be consumed, so the rest of which will feed into the cultivation medium, which in turn will affect the water quality can be eliminated. Under these conditions, the purpose of this study was to determine the level of carbohydrate feed and feeding frequency on the growth rate and the best carbohydrate digestibility of juvenile shrimp vanamei.
feeding frequency 3 times. Thus obtained 12 combined treatment replicates were each given 3 times to obtain 36 experimental units. Data analysis: Data were analyzed using analysis of variance. If the results of the analysis proved that significant treatment followed by Tukey's W-test to determine the treatment that produced the best response.

Specific Growth Rate (SGR)
Specific growth rate of juvenile white shrimp A2B2 highest in the combination treatment, followed by A3B1 and A3B2 with values respectively 9.888 ± 0.083%, 9.244 ± 0.877 and 8.453 ± 0.946%. All three treatment combinations were not significantly different (P>0.05) but significantly different from other treatment combinations (P<0.05) ( Table 3).
The results showed that the specific growth rate of white shrimp juvenile daily highest achieved in the combined treatment 38% carbohydrate content of feed and feeding frequency of 4 times per day. This suggests that the juveniles were able to take advantage of white shrimp feed with feed carbohydrate content to 38% by increasing the feeding frequency of upto 4 times per day. Based on the recommendation of the humans who suffer from diabet, suggested that the feeding frequency is much more then the ability to utilize carbohydrates can be improved. This is in line with research that the continuous feeding may increase the use of carbohydrates and increase fat reserves through increased lipogenesis process. In addition to the feeding frequency more frequently, the possibility of higher feed can be consumed, so the rest of which will feed into the cultivation medium, which in turn will affect the water quality can be eliminated. Increased use of carbohydrates by shrimp is expected to increase levels of carbohydrate and reducing protein content in the composition of artificial feed. Growth performance and feed utilization efficiency is significantly influenced by the level of carbohydrate feed.
However, an increased feeding frequency up to 6 times per day instead give effect to the reduction in the rate of growth (Table 3).

Experimental condition and animal
The container used in this study is 60 cm×50 cm×50 cm sized glass aquarium with a total of 36 pieces each capacity 20 liters. The water used is sea water which has been diluted upto 20 ppt salinity.
Test animals used in this study were white shrimp juvenile (Litopenaeus vannamei) postlarva 25 local stadia. The prawns were taken from the nursery people in Maros. Shrimp is adapted to the type of artificial feed is tested. The stocking density of test animals used were 20 individual/container. Percentage of prescribed daily feeding as much as 10%.

Feed and husbandry
Feed used in this study is the artificial feed composition has been determined and is shown in Tables 1 and 2. Especially for observation digestibility of dry matter in the feed chromium oxide added as much as 0.5%.
In order to achieve the desired objectives of the research, white shrimp juvenile maintained for about two months At the time of maintenance, it is worth noting that the feeding frequency. The daily feeding frequency is performed twice a day, four times a day and six times per day according to the tested treatment. As for sampling weights and measurements performed once every week.

The design of experiments
The experimental design used in this study was a factorial design with completely randomized design basis. The first factor is the level of carbohydrates in the diet are: (A1) Carbohydrate content of feed by 44%, (A2) Carbohydrate content of feed by 38%, (A3) Carbohydrate content of feed by 32%, (A4) Carbohydrate content of feed by 26%.
Each level karbrohidrat given repeat 3 times. The second factor is the feeding frequency, respectively: (B1) feeding frequency of twice per day, (B2) feeding frequency of four times per day, (B3) feeding frequency of six times per day. Each treatment was given repetition   Although shrimp fed with high frequency by consuming large amounts of feed but narrow intervals of frequencies, then feed more quickly through the digestive tract and cause digestive ineffective [16] reported the feeding frequency 2 times per day with a span of 12 hours resulted in the best growth in Lates calcarifer juvenile feeding frequency compared to 3 and 4 times per day with a shorter time span. Based on this it can be explained that the maintenance of white shrimp juvenile feeding frequency 4 times a day is enough to improve growth performance.

Carbohydrate digestibility
The results showed that the combined treatment of carbohydrate level of feed and feeding frequency significantly (<0.05) the digestibility of carbohydrates . Single factor of feed carbohydrate levels had no significant effect (P>0.05), but the frequency factor of feeding a significant effect (P<0.05) the digestibility of carbohydrates. Feeding frequency four and six times per day was not significantly different (P>0.05), but both were significantly different (P<0.05) with the feeding frequency two times a day (Table 4 and Figure 1).
Carbohydrates are a source of cheap energy, but the ability of aquatic organisms, including shrimp to utilize limited. This is due to lack of ability to digest and regulate plasma glucose concentrations. The low digestibility of carbohydrates associated with the availability of the enzyme α-amylase, whereas low concentrations of plasma glucose regulation allegedly caused by a deficiency of the hormone insulin. The results showed that the digestibility of carbohydrates by white shrimp juvenile increases with increasing feeding frequency. Despite this feeding frequency four and six times a day gives the same response. This is in line with research that the continuous feeding may increase the use of carbohydrates and increase fat reserves through increased lipogenesis process. In addition to the feeding frequency more frequently, the possibility of higher feed can be consumed, so the rest of which will feed into the cultivation medium, which in turn will affect the water quality can be elimination. It is seen from ammonia -N excretion were lower in the feeding frequency four times in this study.
The ability to use carbohydrates as an energy source varies between fish, shrimp, and terrestial animals. The use of carbohydrate by fish and shrimp are less efficient than terrestial animals [13]. The use of hot water in the manufacture of pellets was also influential, as it is known that carbohydrates are gelatinized, which increases the digestibility of shrimp [14][15][16]. The results showed that an increase in starch gelatinization for commercial feed manufacturing is expected to have a positive effect on digestibility [17]. Carbohydrates and lipids are important nutritional components in food shrimp [8]. From a practical standpoint, it is worth understanding how carbohydrates are used to provide information in design a better feed for the different growth phases of the shrimp.
The results of the study [17] showed that salinity variations do not affect the digestibility of carbohydrates and lipids by white shrimp juvenile on the container control. The quantity and quality of waste excreted by shrimp depends on consumption, digestion, and metabolism of the compound feed [18,19] reported that the highest energy of feed consumed by white shrimp juvenile Litopenaeus vannamei was obtained when the salinity of the water is maintained at 26 ppt. White shrimp reared in low salinity shown to promote the growth and survival by adjusting the level of nutrients in the feed [20,21]. When the shrimp are exposed to low salinity, shrimp should resist the loss of Na + and Clby the active uptake of Na + from the water in exchange for H+, which occurs in the apical membrane of the cell osmoregulatory to increase capacity osmoregulatory [22][23][24].
During the ongoing research of water quality parameter values remain at the limit eligibility for the growth and survival of white shrimp juvenile especially salinity was maintained in the range of 20 ppt. The values of physical parameters of the water quality is within acceptable limits for maintenance indoor shrimp production [10].

Conclusion
Based on the research that has been done can be concluded that the best level of carbohydrate feed was 38% with a feeding frequency four times a day. Level of 38% carbohydrate feed produces the highest specific growth rate and high carbohydrate digestibility.