SUITABILITY OF REDWORMS, (Eisenia foetida) AS PROTEIN INGREDIENT OF FISH FEEDS FOR NILE TILAPIA AND AFRICAN CATFISH IN GREENHOUSE AND OPEN POND AQUACULTURE SYSTEMS

Abstract

This study assessed the suitability of redworms as a protein ingredient in fish feeds. Furthermore, the study evaluated the use of greenhouse technology to promote aquaculture of warm water fish species in high altitude areas characterized by low temperatures below optimum range of 25 to 33˚C. The study was conducted at the Agro-Science Park’s Fish Farm in Egerton University from January to June 2017. A total of 240 catfish and 240 monosex male tilapia fingerlings were stocked in 30 hapa nets in greenhouse and 30 hapa nets in open pond at a rate of 8 fingerlings per net. Redworms were cultured for use in feed formulation. Two isonitrogenous diets containing 35% and 40% were formulated for tilapia and catfish respectively using redworms and fish meal as animal protein ingredients. Five redworm experimental diets containing 0:100%, 25:75%, 50:50%, 75:25% and 100:0% redworm and fish meal were formulated and fed to fish twice daily at 3% body weight. Selected physico- chemical parameters; temperature, conductivity, dissolved oxygen and pH were monitored daily while nutrients; nitrites, nitrates, ammonia, soluble reactive phosphorus and total phosphorus were analyzed monthly. Fish were sampled every fortnight to determine the Absolute Growth, Specific Growth, Food Conversion Ratio, Length Weight Relationship, and condition factor. There was no significant difference in the mean protein content of redworm meal 62.29±1.13 and fish meal 57.71±0.77 (t-test, df=1, p > 0.05). Similarly, there was no significant difference in mean lipid content of redworm (6.34±0.48) and fish meal (5.51±0.19). Temperature varied significantly in the two pond systems (t-test, p<0.05). There were significant differences in the Specific Growth rate, Absolute growth and mean weight gain of Nile tilapia and African catfish cultured in greenhouse and open pond systems (t-test, df=1, p < 0.05). Fish cultured in greenhouse pond had higher mean weight gain than those in the open pond system. However, there were no significant differences in the specific growth and Absolute growth rates of fish fed on the 5 redworm experimental diets (One Way ANOVA, df ꞊ 4, p ꞊ 0.071). Fish fed on diet containing 50% redworm diet gained highest weight. Nile tilapia and African catfish cultured in greenhouse pond had condition factors of 2.15 and 3.62 respectively while values of 0.87 and 0.88 in the open pond indicating isometric and allometric growth in greenhouse and open ponds, respectively. Calculated Food conversion ratio indicated that both experimental diets were efficiently utilized in greenhouse pond compared to the open pond. Therefore, this study recommends the use of redworm meal as an alternative protein ingredient and use of greenhouses in improving the growth rate of warm water fish species in aquaculture.