Abstract:

Phytic acid is an anti-nutrient found in almost all feed grade plant materials. Phytic acid
binds with nutrients to form complexes that are poorly digested by fish.To increase
bioavailability of nutrients from such complexes, diets of 33%, 37%, 50% and 65% crude
protein (CP) were made out roasted ingredients. The diets were mixed with phytase.
protease and sprouted sorghum and evaluated with African catfish (Clarias gariepimis) in
four cascading experiments. Phytic acid, CP content, pH, digestibility of protein and
phosphorus were determined in the diets. Then growth performance of catfish hatchlings
fed on 65% CP diets mixed with protease and that of catfish fingerlings fed on 33% and
37% CP was determined. Results showed that roasting feed ingredients significantly
reduced phytic acid (from 5.89 ± 0.04% to 5.67 ±0.04 %) while dietary phytase in 33%
and 37% CP diets and protease in 50% and 65% CP significantly increased digestibility
of protein and phosphorus. Phytase increased digestibility of protein from 75.07% to
96.50% and phosphorus from 74.44% to 98.50%. On the other hand, feeding catfish
hatchlings on dry diets with 1250 units of protease signifacntly (p < 0.05) enhanced their
survival and weight gain from 11% - 42% and !5-296mg respectively. Growth of catfish
fingerlings fed on 33% and 37% CP diets mixed with phytase was also significantly
enhanced (p 0.05; 174.40-164.04g) in ponds. The cost benefit ratio of pond catfish was
significantly higher (p< 0.05; 6.30 ) with 33%CP diets incoporated with 1000 phytase
unitsk'g'1. These results demostrare that supplemental protease can enhance use of high
protein dry diets as catfish starter diets and phytase use of low protein diets as fattening
diets. It was therefore recommended that in addition to roasting diet ingredients, prolease
be used as a micro additive in catfish starter diets and phytase enzyme in grovv-out diets.