The Cricket (Gryllus assimilis) as an Alternative Food Versus Commercial Concentrate for Tilapia (Oreochromis sp.) in the Nursery Stage

In this paper, a 32% commercial diet of protein for tilapia fingerlings (Oreochromis sp.) commonly used in fish farms in the country and cricket meal in a mixture with 32% corn flour as a protein was compared alternative food The breeding, raising and fattening unit of crickets (Gryllus assimilis) was implemented for its subsequent sacrifice and transformation into flour and used as a source of protein in the diet, these gained a weight of 0.70 g. To accommodate the fry, plastic tanks with a capacity of 1 m were used, the water was sucked by means of an electric pump; with permanent aeration where 15 individuals of red tilapia per m were planted with an average weight of 5 g which reached an average weight/fish/day of 26 g, a growth/fish/day of 0.86 g, the total biomass was 340 g, and a feed conversion factor (FCA) of 1.16. According to the Student’s T analysis and a comparison of means, no differences were found, with a correlation of 83.1% between the food supplied and the increase in weight, the water parameters were found at an optimum level. The protein percentage of cricket flour ranges between 15% and 80% depending on the geographical area, those that were used in the local ration have 58.16% of crude protein and 9.32 of protein nitrogen, the two rations in comparison had a protein content of 32%.

Honduras, is mainly developed in coastal areas of Honduras, there are 1589 producers that generate 19,000 direct jobs and 50,000 indirect, with an annual production of 29 thousand tons currently in an area of 82,512 hectares, being the largest exporting country of Tilapia for the Europe, Asia and united state who is the world's largest consumer of fresh tilapia (Toledo-Pérez & García-Capota, 2000).
The objective of this work is to know the growth of tilapia fingerlings (Oreochromis sp.) in controlled environment feeding on cricket meal (Gryllus assimilis) as an alternative food compared to the growth of commercial rations elaborated for the culture of pond fish and commonly used by the local fish farmer.

Local
The work was developed in the National University of Agriculture, department of Olancho (Honduras), located 6 km southeast of the city of Catacamas, developing in two stages, the first stage being to create and reproduce crickets and the second stage in the fish farming section where the productivity indicators and the environmental conditions of water quality were monitored in the form of shelter for the fingerlings of tilapia.

Reproduction and Breeding of Crickets (Gryllus assimilis)
In the first place, the crickets were collected in the grounds of the National University of Agriculture, and later identified in the entomology laboratory of the aforementioned institution, conditioned in plastic boxes of 37.5 L in a ratio of 30:3, that is to say thirty females for three males with water and foods such as fruits, concentrate and concentrated vegetables.
Fifty breeders were selected (those who were in stable physical condition and those who had reached sexual maturity in 40 days), leaving the crickets for four days to fecundate the females. As an egg laying material, 250 mL disposable cans were used, which were modified with holes in the contour to allow oxygenation and filled with coconut substrate for oviposition of eggs, with the coconut substrate previously sterilized, followed by Isolation of the females for two days in individual cages, being counted between 800-1000 eggs per posture per female.
At the birth of the micro-crickets, they were collected and moved immediately to maintenance boxes of 37.5 L and were conditioned with 400 g of food wheat bran, providing water daily by sprinkling on the walls of the box thus preventing waterlogging, bottom of the box, carrying this stage a period of 20 days.
Subsequently, the 30-day-old micro-crickets were transferred to 37.5 L fattening boxes previously disinfected and conditioned, creating ideal conditions for the correct development of the cricket. In each box, a weight of 54.48 g of cricket was installed, with an average weight of each animal of 0.01 g, which is equivalent to 5448 cricket. Those boxes remained for 70 days with an average temperature of 26 °C and a humidity of 66%.

Process of Cricket Flour Preparation (Gryllus assimilis)
Once the growth was completed for 70 days, the crickets were sacrificed by exposure to low temperatures at 0 °C, causing a thermal shock and in this way their metabolism was reduced and induced a state of lethal hypothermia. Later, the crickets were introduced in boiling water at 80 °C for 2 minutes to soften the exoskeletons and reduce microbial growth.
Subsequently, the crickets were placed in an oven for 50 °C for 16 hours to be dried and then centrifuged for particle homogenization. The sample was sent to the quality control laboratory S. José de Tegucigalpa (Honduras), where it was evaluated by chemical analysis to determine its quality as an alternative food, considering the protein content as the main parameter.

Preparation of Lifting Units of Red Tilapia Fingerlings (Oreochromis sp.)
Once the number of crickets corresponding to the rest of the evaluation days was obtained, the fattening unit was assembled, installing two bins with water storage capacity of 1 m 3 in which the re-seeding of tilapia was done in the nursery phase, whose unit has a water exchange system, permanent aeration system to ensure adequate levels of oxygen, a bird protection system was used to prevent losses caused by predators and once the water quality was verified, it was acceptable. He made sowing of fingerlings with density of 15 individuals per bin, being evaluated during 60 days with an initial weight of 5 grams.

Feeding the Red Tilapia Fingerlings (Oreochromis sp.)
The feeding was provided in a single daily ration, starting with the amount of 8 grams of food (RC) commercial ration and (RL) local ration cricket meal and cornmeal both at 32% protein for a period of 15 days, then a decrease to 7 grams of food for a period of 15 days and from day 31 the food was supplied as required by the fry jas.ccsenet.org Journal of Agricultural Science Vol. 11, No. 6;2019 of each tank, which were 16 g from day 31 to day 45 and 30 g from day 46 to day 60, the feeding was done taking advantage of the hours with greater solar radiation, supplying the same amount for both groups in the form of a mass inside a feeder to avoid the waste of food.
The elaboration of the mixture of the local ration was determined through a mass balance exercise for two ingredients which are complemented to obtain the desired level of a nutrient, the cricket meal used in the local ration contains 58.16% protein raw and 9.32% protein nitrogen.

Variables to Be Evaluated in Red Tilapia Fingerlings (Oreochromis sp.)
The parameters evaluated were: average weight (grams), growth in day (grams), total biomass and food conversion factor according with Santos (1978) and Swingle (1961 (2) where, CPD = Growth in gr/fish/day; Xpm= Average/fish to the sample; Xps = Average/fish at planting ; Tsm = Average/fish at planting.

Total Biomass
It is calculated by weighing the total number of individuals captured from sowing to partial or final sampling by multiplying the fish average to the sample by the number of fish sown minus mortality: where, Ns = Number of fish planted; M = Mortality; Xpm = Average/fish to the sample.  (4) where, FCA = Conversion factor.

Water Quality Parameters
They were measured as water quality parameters (temperature, pH, turbidity and dissolved oxygen). The temperature of the water was directly taken with a thermometer, making different shots and taking an average (between 07:00 AM and 06:00 PM), pH measurements of the water were also taken by taking a daily sample of both tanks by 60 days, the water samples for the dissolved oxygen analysis were taken once a week in both tanks, the measurement of the turbidity was once a week using the water exchanges were made in 3-day intervals during 60 days (Macedo, 2008).

Statistic Analysis
The results were analyzed from Student's T tests in Excel and the IBM program, SPSS, version 22.0, using statisticians, descriptive statistics, normality tests, homogeneity of variance and correlation tests. Table 1 shows the different growth indicators of red tilapia in plastic tanks with a capacity of 1 m 3 for 60 days in the fish section of the National University of Agriculture in Catacamas Olancho, Honduras.   the fry, does not affect the quality of the water, nor does it diminish the nutritional and commercial value of the meat of the fish since it was found in a range of 20-30 UNT.

Growth Indicators of Red Tilapia (Oreochromis sp.)
Dissolved oxygen (DO) is one of the most important water quality parameters, since it indicates the contamination of the same, being that the waters that present low values of DO, are caused by the presence of organic matter or material oxidized (Posada et al., 2013). The concentration of dissolved oxygen contained in the water samples determined that the levels found are adequate for the development of the fry. Tilapia supports levels of 1 mg L -1 of oxygen, in the absence of light of 2 to 3 mg L -1 , but the optimal level is of 8 to 12 mg L -1 , they develop in a good way in the latter, they were not found critical levels of dissolved oxygen, these samples were taken at different times of the day and with different conditions of the time.

Conclusions
According to the growth comparison between the supply of cricket meal with corn flour and commercial ration to the tilapia fingerlings, it was determined that there are no significant growth differences.
The physicochemical parameters of the water did not affect the development of the individuals, nor did they cause physiological alterations that could directly or indirectly affect the fry because all the parameters are within an acceptable range.
The local ration consisting of cricket flour (Gryllus assimilis) and nixtamalized corn flour, can be a viable alternative for its high content of nutrients mainly protein, fatty acids and fiber, if the fish farmer has his own source of flour supply crickets The physicochemical parameters of the water did not affect the development of the individuals, nor did they cause physiological alterations that could directly or indirectly affect the fry because all the parameters are within an acceptable range It was determined that the survival rate was high, in both groups of individuals, which indicates that they developed in an adequate environment and took advantage of the food supplied.