Effects of Fermented Fresh Cassava Residue as a Partial Replacement for Commercial Feed on Growth Performance, Feed Utilization, Carcass Composition and Economic Efficiency of Rice Field Crab (Sayamia bangkokensis)

HistoryThis study investigated the effects of fermented fresh cassava residue (FFCR) as a partial replacement for commercial feed on growth performance, feed utilization, carcass composition, and economic efficiency of rice field crab (Sayamia bangkokensis).Fresh cassava residue was fermented for seven days using Effective Microorganisms (EM) and molasses, resulting in improved nutritional quality, including an increase in crude protein from 2.68 to 5.94%, a reduction in crude fiber from 18.62 to 14.37% and a marked decrease in hydrogen cyanide (HCN) from 82.43 to 18.27 ppm.A total of 240 crabs (initial weight 30.0±1.5 g) were randomly assigned to four dietary treatments with three replicates: T1 (100% commercial feed), T2 (67% commercial feed +33% FFCR), T3 (33% commercial feed +67% FFCR), and T4 (100% FFCR), over an 8-week feeding trial.Results indicated that crabs fed T2 exhibited the highest final weight (51.86±2.34g), weight gain (21.78±1.63g), specific growth rate (0.98±0.05% day⁻¹), feed efficiency (51.12±2.67%)and protein efficiency ratio (1.54±0.08),with no significant difference compared to the control group (P>0.05).In contrast, higher FFCR inclusion levels significantly reduced growth performance and feed utilization (P<0.05).Survival rate remained high (85-95%) and was unaffected by dietary treatments.Muscle crude protein content was maintained at moderate inclusion but declined at higher substitution levels.Economic analysis demonstrated that T2 achieved the lowest economic conversion ratio (1.39±0.06)and the highest profit index (3.12±0.14).Pearson correlation analysis confirmed strong positive relationships among growth performance, feed utilization, and economic return.In conclusion, 33% replacement of commercial feed with FFCR is optimal for maintaining growth and carcass quality while improving feed efficiency and profitability in rice field crab culture.