Effect of Using Low-Protein Diets in Semi-Intensive Pond Cage Culture of Tilapia, Tilapia rendalli (Boulenger)

ABSTRACT

An experiment was carried out to determine the effect of using low-protein diets on production of Tilapia rendalli in semi-intensive pond cage culture. This was carried out at Bunda College of Agriculture's fish farm, University of Malawi, where two 200-m² earthen ponds of 1-m depth were used for two months from February 2003 to early April 2003. Each pond had 6 cages of 1 m³ in size stocked with 15 fish, each 4.8 ± 1.2 g average weight and 6.7 ± 0.6 cm average length. Chicken manure was used as the organic manure applied at 500 kg/ha/wk and also acted as a control. All treatments were replicated three times. It was observed that fish growth was higher in the soybean meal-based diet, with final weight of 34.4 g, followed by sunflower cake, with final weight of 23.3 g. The lowest was 14.4 g in the chicken manure only, and cottonseed-based diet had final weight of 19.5 g. These results also agree with the specific growth rate (SGR) that ranged from 2.1%/day in the cages only fertilized with chicken manure to 3.6%/day in the soybean-based dietary treatment. The lowest feed conversion ratio of 1.2 was also observed in the soybean-based dietary treatment. This suggests that the use of lower protein diets that contain soybean would produce better results and may increase yield when combined with fertilization, as evidenced by high fish survival rates of more than 93% in all treatments.

KEYWORDS:

• Cages
• low-protein diet
• Tilapia rendalli
• ponds
• small-scale farmers
• semi-intensive system

ACKNOWLEDGMENTS

The author would like to thank Canadian International Development Agency (CIDA) for sponsoring the research and Bunda College, University of Malawi, for allowing me to use the research facilities. Late Mr. A.G. Matambo and his staff at the aquaculture farm are also thanked for the technical support rendered throughout the experimental period. Finally, Mr. E. Nyali will be remembered for the hand given during laboratory work.