Effect of some common West African farm-made feeds on the oxygen consumption and ammonia excretion rates of Nile tilapia, Oreochromis niloticus

The effects of two common West African farm-made feeds on postprandial metabolism were assessed in adult Nile tilapia (Oreochromis niloticus) by quantifying the oxygen consumption rates (MO2) and total ammonia-nitrogen (TAN) excretion over a 24-h period. Measurements followed the ingestion of a single meal of a fishmeal-based control diet and two diets containing 30% copra (CM) or palm kernel meal (PKM) inclusions by groups of 15 adult O. niloticus per tank.

The mean net MO2 (postprandial oxygen consumption corrected for routine metabolic rate) during digestion for the different tilapia groups varied narrowly between 112.2 ± 9.9 and 129.9 ± 20.4 mg O2 kg−1 h−1 with the fish fed the CM diet recording a significantly lower (p = 0.04) net MO2 response relative to the other two diets.

Net TAN excretion rates of the different dietary groups varied between 3.4 ± 1.4 and 4.4 ± 1.6 mg TAN kg−1 h−1. Under the standardized experimental conditions, copra and PKMs appeared to be promising candidates as partial replacements to fishmeal in tilapia diets as far as rates of oxygen consumption and ammonia-nitrogen excretion are concerned.