Growth performance and nutrient utilisation of Clarias gariepinus fed on sweet orange peels (Citrus sinensis) as carbohydrate source

Abstract

The effect of substitution of maize meal with orange peel in the diet of Clarias gariepinus was investigated. Proximate composition, anti-nutritional content of differently processed orange peels and their effects on the growth of Clarias gariepinus were investigated. Soaked sweet orange peel meal was used in the formulation of the experimental diet and replaced maize at 25, 50, 75, and 100% inclusions respectively while the control diet was at 0% SOPMs replacement. The experiment consists of five treatments (1, 2, 3, 4 and 5) with two replicates in a completely randomized design (CRD). Two feeding trials lasted for a period of 8 weeks (56 days) and was carried out in a concrete experimental pond measuring 2 m x 1 m x 0.5 m. Two hundred Clarias gariepinus fingerlings, 10 g average weight were randomly distributed at 40 fish per replicate. Growth responses were checked and recorded weekly with a sensitive weighing balance (Mettler 5000) to the nearest grams after which feed quantity was adjusted. Fish were fed experimental diet twice daily (08:00 am and 05:00 pm) at 5% body weight, pond water was changed weekly during weight recording and the water quality parameters were monitored. The results of the proximate analysis of orange peel meals under different processing methods indicated that moisture content was highest in sundried peels (6.74) and lowest in cold-soaked peels (5.8%). Lipid content was highest in boiled peels (8.47) and lowest in fermented peels (7.71%). Protein content was highest in boiled peels (7.43) and lowest in sundried peels (6.40%). The highest NFE was recorded in the sundried peels (60.90) while lowest NFE value was recorded in the fermented (54.38). The anti-nutritional factors determined from the various processing method showed that boiling was more effective in reducing tannin (46.4% reduction), phytic acid (46.5% reduction), oxalate (54% reduction) and was least effective in reducing saponin (20% reduction). Fermentation was least effective in ANF reduction, tannin (21%) and phytic acid (15%); cold-soaking was more effective in saponin reduction (46.5%). Result obtained revealed that there was no adverse effects on the growth performance of the fish fed orange peel meals at 50% inclusion, thus sweet orange peel meals can replace maize up to 50% level of inclusion in the diet of Clarias gariepinus fingerlings without adverse effect with a corresponding SGR of (2.64±0.00). Apparent net protein utilization differed among the treatments (p<0.05).