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.