Enhancing the Feed Value of Eichhornia crassipes through Processing: Nutritional Composition, Anti-Nutritional Factors and In vitro Protein Digestibility

Water hyacinth (Eichhornia crassipes) is a rapidly growing aquatic plant with potential as an unconventional livestock feed resource, although its high fibre content and anti-nutritional factors may limit nutrient utilisation. This study evaluated the effects of boiling, oven drying, and solid-state fermentation on the nutritional composition, fibre fractions, free amino acids, selected anti-nutritional factors, and in vitro protein digestibility of Eichhornia crassipes collected from Anantigha, Cross River State, Nigeria. Fresh samples were divided into untreated control, boiled at 100°C for 2 hours, oven-dried at 100°C for 2 hours, and fermented at ambient temperature for 48 hours. The processed samples were analysed for nitrogen, protein, free amino acids, crude fibre, neutral detergent fibre (NDF), acid detergent fibre (ADF), tannin, cyanogenic glycosides, phytate, oxalate and sequential pepsin-pancreatin protein digestibility. Data were expressed as mean ± standard deviation and analysed using one-way ANOVA followed by Tukey's HSD test at p < 0.05. Oven drying retained relatively high protein and nitrogen contents (46.93 ± 0.58% and 7.51 ± 0.09%), whereas fermentation recorded the lowest values (16.72 ± 0.10% and 2.68 ± 0.02%). Fermentation produced the greatest reductions in crude fibre, NDF and ADF, with values of 31.70 ± 0.26%, 54.32 ± 0.86% and 33.84 ± 0.69%, respectively. Free amino acids were highest in the control (1270.40 ± 0.97 mg/L), while fermentation retained the highest concentration among processed samples (270.62 ± 0.35 mg/L). Boiling produced the greatest reductions in tannin and cyanogenic glycosides, while fermentation markedly reduced phytate. Oxalate was not detected in processed samples. Final protein digestibility was highest after fermentation (74.63 ± 0.82%), followed by boiling (68.47 ± 0.76%) and oven drying (62.83 ± 0.69%). Overall, processing substantially improved the nutritional quality and digestibility of Eichhornia crassipes, with fermentation particularly enhancing fibre reduction, phytate removal, and protein digestibility.