APPLICATION STUDY FOR PRODUCING ECO-FRIENDLY DIET FOR FISH FROM THE BLUE GREEN ALGA SPIRULINA PLATENSIS

Abstract

Spirulina platensis is a filamentous Cyanobacterium with nutritive value, can easily be cultivated with cost effective medium. The present study was carried out in Keram fish farm, Behira Governorate to produce a large scale biomass of Spirulina platensis with a high quality of protein in fish diet. The nutritive value of the protein is due to its amino acids contents ranged from 48.59 to 49.65 mg/g. In this study modified Zarrouk medium was used by replacing the source of water by underground water and the source of phosphorus by using phosphoric acid (80 ml/m3). Also in this study a complete replacement of fish protein by Spirulina platensis powder in the fish diet (formulated diet) for Oreochromis niloticus was done and a comparison was carried out between the two diets. It has been found that one ton of S. platensis powder with about 65% protein can be produced from 200 m3 medium / month with cost of 1 1060.5 E.P. for farm scale and 7371 for industrial scale while with fish protein was 14500 E.P. Physico-chemical measurement of pH, temperature, turbidity, Chl- a, blue green cells, of the ground water during the production of S. platensis were carried out by using Manta 2 water quality sonde every 30 min. for 30 days. Chemical parameters as ammonium, nitrite, nitrate and orthophosphate are also analyzed. Drying processes were done at open air, 60 oC and 120 oC to choose the best drying process for S. platensis without affecting its bio- chemical contents. 120 oC was the best drying temperature as i manufacturer phase but in farms air dry can be used as a low cost process but with using some precautions. The phycocyanin percentage in fresh sample was 100% while it decreases with increasing the drying temperature till reached 38% at 120 oC. The maximum values of chl-a μg/l were measured 2648.3 and 2620.8 μg/l on the 12th day for the new tested medium and modified Zarrouk medium respectively. Growth performance of Nile tilapia fingerlings was observed during the experimental period (120 days), at the end of the experiment. The results revealed that significant value (p< 0.05) between the diets used in progress mean of fish weight /g during the experiment. Significant value (p<0.05) observed on final body weight which revealed that 70.66 g and 58.763 g for fish diet 2 (with Spirulina protein) and diet 1 (with fish protein) respectively. Also weight gain with significant value p< 0.05 for the two types of diets .The results revealed that significant value P< 0.05 in average daily gain (ADG) and feed conversion ratio (FCR) where the ADG was 0.546 and 0.450 g/fish /day for diet 2 with S. platensis protein and diet 1 with fish protein respectively. The values of water contents in the fish ponds (fed on diet 2) were lower than that fed on diet 1, where the average ammonium values were 0.6998 and 0.6466 mg/l for diet 2 and diet 1 respectively. Also the average of nitrite was 0.274 mg/l for diet 2 and 0.254 mg/l for diet 1 and nitrate was observed that the value of diet 2 (0.7354 mg/l) lower than that for diet 1 (0.8006 mg/l). It has been found that there is no effect of Spirulina diet on the water quality compared with control diet.