This study investigated the effects of a plant-based diet supplemented with phytase and mannan oligosaccharide (MOS) on the growth, feed utilization, fatty acid profile, hematology, and intestinal morphology of Chamo strain Nile tilapia Oreochromis niloticus (L.) fry. Plant-based experimental diets were formulated to contain 0% (control), 6 g kg-1 MOS, 1000 phytase (phytase unit) FTU kg-1, and a combination of 6 g kg-1 MOS and 1000 phytase (FTU kg-1). Inclusion of Phytase alone or combined with MOS had improved growth performance parameters. MOS alone or combined with phytase had improved lipid quality compared to other groups.
The fish fed with phytase or combined with MOS had higher crude protein and ash content than other groups. The inclusion of a combination of MOS and phytase in the feed increased values of villi length, villi width, and goblet cell numbers of the intestine. Supplementation of additives also improved some hematological parameters. The results suggest that MOS and phytase supplements can enhance the growth performance, health status, and nutritional value of Nile tilapia fed a plant-based diet. However, further studies are needed to optimize the dosage and duration of these supplements and to evaluate their effects on other aspects of fish physiology and behaviour.