Abstract:

Locally available nutrient materials (Cow dung, Soybean extracts and Diammonium Phosphate (DAP)ZUREA inorganic fertilizer) were used to prepare culture media for growing Chlorella spp. as a food base for rotifer culture and compared to the commonly constituted Bold’s Basal Medium (BBM) as a control. The production rate of Chlorella spp., the effect of intrinsic ammonia and pH on culture performance, duration of culture cycle as well as the differences in resultant fatty acid composition of the algae were tested. The production rate of B. calycijlorus fed on this Chlorella grown under the four media and the cost effectiveness of using each of the media were investigated. Experiments on algae culture were set in 25L rectangular glass tanks, with 24hour illumination and aeration. Daily reading of ammonia, pH and counts of algae cells/ml were carried out. On the other hand, 10L plastic jerry cans, supplied with 24hour mild bubbling were found suitable for rotifer culture. Daily changes in rotifer density (rotifers/ml) and number of eggs carried per rotifer were recorded. Soybean extract attained the highest density of Chlorella per ml, followed by Cow dung and DAP/UREA, while BBM showed least performance. There was a notable positive effect of pH on growth of Chlorella. On the other hand, ammonia did not have much impact even at relatively high concentrations (236.095 mg I'1 in DAP/UREA). Chlorella was found rich in various fatty acids but with a predominance of polyunsaturated fatty acids (>40percent of Total Fatty Acids) in all media. Monounsaturated fatty acids (MUFAs) were recorded low (<5percent TFA) for Cow dung, BBM and Soybean. DAP/UREA was superior for MUFAs and HUFAs. Comparably, DAP/UREA was found to have about half the quantity of saturated. fatty acids (SFA) found in the other three media. The highest number per ml of B. calyciflorus was found in the culture grown on Cow dung. This culture also sustained a much healthier culture in terms of production of eggs per rotifer and was also the most cost effective. Further research on how these recorded performances translate into healthy larval fish is required.