Development of feeding protocols for Tilapia rendalli in Malawi reared in semi-intensive culture systems

Kang'ombe, Jeremiah (2004) Development of feeding protocols for Tilapia rendalli in Malawi reared in semi-intensive culture systems. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

Tilapia is the major group of fish used in aquaculture in Malawi and its potential has never been realised. Previous research has focused on improving the growth performance. Nutritional studies were carried out to determine and improve feeding protocols in order to enhance the growth of Tilapia rendalli. The first experiment was on the effect of using different organic manure. T rendalli in the chicken manure treatment were significantly larger and had higher net annual yields than those in cattle, pig manure and no-manure treatments. Significantly higher amounts of chlorophyll a and numbers of zooplankton were found in ponds fertilized with chicken manure. -- In the second experiment, T rendalli were evaluated in ponds fertilized with chicken manure to determine the effect of using different single ingredient supplements. T rendalli in the soybean treatment were significantly larger and had higher net yields than in maize bran, rice bran and unsupplemental, chicken manure treatments. -- The third experiment was set up to determine the effect of different temperatures. T. rendalli in the 32°C treatment were significantly larger than those in 24, 28°C and ambient temperatures. Fish cultured at 32°C had significantly higher digestibility coefficients, lower feed conversion ratios, higher feed conversion efficiency and protein efficiency ratios. The last experiment examined the effect of different salinities. T. rendalli in the 10 0/00 grew significantly larger than those in the freshwater, 5 0/00, and 15 0/00. Fish cultured in 10 0/00 salinity had significantly higher digestibility coefficients, lower feed conversion ratios, higher feed conversion efficiency and protein efficiency ratios. The survival of the fish was significantly different among salinity levels decreasing from 100% in freshwater to 66.7% in 15 0/00 salinity treatment. -- The overall results suggest that the use of chicken manure would produce better results than cattle and pig manure treatments, and ponds fertilized with chicken manure may be supplemented with soybean to increase yield. Water temperature of 32° C and salinity level of 10 0/00 may be optimal for T. rendalli because feed conversion was higher, and digestibility coefficients were higher for protein, fat, ash and gross energy under these conditions.

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