The possibility of molluscan shell powders as organic mineral sources in Nile tilapia diets: Effects on growth and health status, body physiology and economic performance

This study investigated the potential of using molluscan shell powders as alternative organic mineral sources in aquaculture feed. Four isoproteic diets (32 % crude protein) were formulated for Nile tilapia ( Oreochromis niloticus ): a control diet (T1) containing a commercial mineral premix, and three experimental diets incorporating shell powder from giant freshwater snail (T2), river snail (T3), and freshwater mussel (T4) as primary mineral sources. A 90-day feeding trial assessed the effects of these diets on growth performance, feed physical properties, whole-body composition, blood biochemistry, liver and intestinal health, and economic efficiency. The findings revealed that significant variations (p < 0.05) were found in the mineral contents among the different molluscan shell powders. Most feed physical properties were not significantly affected (p > 0.05) by the dietary treatments, although differences were observed in the pellet durability index. Growth parameters, including final weight, weight gain, specific growth rate, and total biomass, were significantly higher (p < 0.05) in fish fed diets containing molluscan shell powders (T2-T4) compared to the control group (T1). Analysis of the whole-body composition revealed significant differences (p < 0.05) in ash content, with the control group showing the lowest value. Blood haemato-biochemical profiles were significantly influenced (p < 0.05) by the different experimental diets, with some exceptions. Fish fed T1-T3 diets demonstrated improved intestinal health, characterized by an intact epithelial wall, well-organized goblet cells, and distinct stratum compactum as well as tunica muscularis. Organic mineral-based diets significantly affected (p < 0.05) the villi width and crypt depth. Additionally, liver health was markedly enhanced in the T2 group. Nevertheless, moderate liver health was observed in the T3 and T4 groups compared to the control. Economic efficiency demonstrated a considerable improvement (p < 0.05) in the group fed diets incorporating organic mineral sources. In conclusion, the inclusion of a mineral premix derived from molluscan shells in Nile tilapia diets significantly improved growth, whole-body composition, blood biochemistry, intestinal and liver health, and economic efficiency under culture conditions. • Growth parameters, including final weight, weight gain, specific growth rate, and total biomass, were significantly higher (p < 0.05) in fish fed diets containing molluscan shell powder. • Fish fed with molluscan shell powder improved intestinal health and blood haemato-biochemical. • A mineral premix derived from molluscan shells in Nile tilapia diets significantly improved economic efficiency under culture conditions.