Effects of Protein, Lipid, Feeding Levels and Their Interaction ... 67Table 1. Formulations and proximate composition of experimental diets
(% dry matter)Ingredient (%) CP35CL12 CP35CL8 CP25CL12 CP25CL8
Fishmeal 21.10 21.10 14.10 14.10
Cassava
Oil mixture^
Cellulose
Basal mixture
Proximate composition
(%)
Crude protein
Crude lipid
Moisture
Ash
Energy (kcal/100g diet)^325.20
10.30
9.80
5.7034.95
12.56
12.75
8.30
355.641.10
4.30
0.00
5.7034.86
8.44
8.73
8.28
352.744.70
10.80
6.10
5.7024.91
11.98
8.79
6.30
353.356.80
4.80
0.00
5.7025.14
8.61
8.56
6.23
350.8(^1) Lipid source: corn oil.
(^2) Basal mixtures: Calcium phosphate 0.50%; Choline chloride 0.70%; Vitamin mixture
1.50%; Mineral mixture 3%.
(^3) Energy was calculated according to Anderson et al. (1991) cassava and fishmeal;
Boscolo et al. (2002) for oil.
Corn oil was added to each diet to provide the lipid content of the diet.
Each crude protein level had two different lipid levels (12% and 8%). The four
different diets were as follows: CP35CL12, CP35CL8, CP25CL12, CP25CL8.
The diets were prepared by mixing the ingredients in a mixer. When the
ingredients were thoroughly mixed, oil and water were added to obtain moist
dough which was then made into pellets through a meat mincer, with a 3 mm
size. The feed was oven dried at 70^0 C for gelatinization of starch for 2 hours
and then at 40^0 C overnight to ensure proper drying. The feed was kept in a
refrigerator at 4^0 C and the required amount periodically taken for feeding.
O. niloticus fingerlings (15.63 ± 0.40g) were obtained from Kegati
hatchery. They were acclimatized in the holding tanks for two weeks then
stocked for the experiment. At the start of the experiment, individual weight
and length of all the fish used in the experiment were taken. The acclimatized
fish were randomly distributed in the 33 hapas at a stocking density of 300
fish per hapa. The sizes of the hapas were 8 m^3. Water quality was monitored
in the morning and evening, just before feeding. Fish were sampled monthly
for growth rate.