Abstract:

Supplementary feeds, either single or multi-ingredient, are used to improve fish yields in fish farming systems. Protein-rich ingredients are highly recommended for better performance (growth) of fish. In Uganda, due to high expense of ingredients rich in proteins for example “mukene” (Rastrineobola argentea), and the lack of suitable alternatives, farmers tend to use carbohydrate-rich maize bran, a cheap ingredient leading to low farm yield. The major objective of the study was to evaluate P. adusta as alternative protein source in feed for Nile tilapia (Oreochromis niloticus). Specific objectives were: to determine and compare nutrient content in “mukene”, P. adusta, and maize bran; to monitor and compare (weekly) weight and length gains of O. niloticus fed on three formulated experimental diets: i) 40% protein diet composed of “mukene” and maize bran; ii) 40% protein diet composed of P. adusta and maize bran, iii) maize bran only. Observations were also made on the behaviour of O. niloticus fed on the different diets. Experimental glass tanks were used for the study over a 10-weeks period. Results indicated 64.5%, 46.4% and 8.8% crude protein in “mukene, P. adusta, and maize bran respectively. Total carbohydrate values were 33.5% in maize bran, 7.0% in P. adusta and 4.8% in “mukene”. Lipids constituted 13.4%, 9.5% and 7.9% in “mukene", P. adusta, and maize bran respectively. Fish were successfully conditioned to the diets. Fastest conditioning was in fish fed on “mukene” mixed with maize bran, followed by those fed on a mixture of P. adusta and maize bran. Results of SPSS One-Way ANOVA at 95% Confidence Interval indicated significant differences in weight gain. Coefficient of Correlation was strongest in a mixture of “mukene” and maize bran (gained 11g) followed by P. adusta and maize bran (gained 7g) and lastly maize bran only (gained 2g), with R values of 0.77, 0.52, and 0.48 respectively. Therefore, P. adusta can be efficiently utilised as an alternative protein source.