Evaluation of Apparent Digestibility Coefficients of Locally Available Caterpillar and Fishmeal Sources From Zambia in GIFT Nile Tilapia (Oreochromis niloticus)

Abstract

High feed costs driven by reliance on imported ingredients hinder aquaculture development in Zambia. Locally available animal protein alternatives offer a promising solution, but their digestibility remains underexplored. This study evaluated the apparent digestibility coefficients (ADCs) of two local caterpillars: mopane caterpillar or vinkubala (Gonimbrasia belina) and silkmoth caterpillar or tukanja (G. zambesina), as well as three small fish species, namely kapenta (Limnothrissa miodon), kakeya (assorted fish), and chisense (Potamothrissa acutirostris), for potential inclusion in juvenile GIFT tilapia (Oreochromis niloticus) diets. A reference diet with yttrium oxide (Y₂O₃) as a digestibility marker and test diets (70% reference diet, 30% test ingredient) were used. Fish were fed at 90% satiation for 6 weeks, with feces collected in the last 2 weeks. The ADC of the test diet ranged from 98% to 99% for dry matter (p  > 0.05), while crude protein (80%–92%), crude lipid (90%–97%), and energy (78%–89%) were significantly different (p  < 0.05), reflecting the effective utilization of these ingredients in the diet. The ADCs of the tested ingredients showed numerical differences, but high variability in standard deviations resulted in no statistical significance (p  > 0.05). ADC of dry matter ranged from 54% to 62% in caterpillars and 67%–81% in fish, crude protein from 62% to 65% and 68%–82%, crude lipid from 66% to 74% and 68%–83%, and ash from 60% to 69% and 74%–83%, respectively. These findings highlight the potential of locally available Zambian ingredients to support sustainable and cost-effective aquafeeds for tilapia. However, the variability in digestibility values indicates the need for further investigation to optimize their inclusion in diets.