Nutrient composition and heavy metal accumulation in water hyacinth [ Eichhornia crassipes ( Mart. ) Solms ] and water lettuce ( Pistia stratiotes L.) from the Dande River, Nepal: Implications for use as alternative feed resources

Background The proliferation of invasive aquatic macrophytes poses a significant ecological challenge globally, while many tropical regions face chronic shortages of affordable livestock feed. This study addresses this dual problem by assessing two invasive species, water hyacinth ( Eichhornia crassipes ) and water lettuce ( Pistia stratiotes ), from the Dande River in Nepal. The objective was to evaluate their potential as a sustainable feed resource by comparing their nutritional and mineral profiles against their heavy metal and mycotoxin contamination. Thirty‐five samples of each species were subjected to a comprehensive analysis. Results The analysis revealed promising nutritional compositions on a dry matter basis. P. stratiotes had a higher mean crude protein (CP) of 19.89%, while E. crassipes contained 17.17% CP. Both species were rich sources of essential macrominerals, especially potassium (K). Mycotoxin screening showed Aflatoxin B1 and B2 levels were below the detection limit of 1.0 μg/kg. However, a critical toxicological barrier was identified. While arsenic and lead levels were within permissible limits, cadmium (Cd) was dangerously elevated. The mean Cd concentration was 0.15 μg/g in E. crassipes (7.5 times the World Health Organization [WHO] limit) and 0.98 μg/g in P. stratiotes (49 times the WHO limit). Conclusion Despite their nutritional merits, the biomass of both species from the Dande River is unequivocally unsafe for direct use as animal feed due to the severe risk of cadmium poisoning and food chain contamination. This study underscores the need for site‐specific safety assessments and recommends that this invasive biomass be redirected towards non‐food valorization pathways, such as biogas production.