Apparent digestibility of selected animal protein sources for mud crab Scylla paramamosain

This research assessed the apparent digestibility coefficients (ADCs) of six animal protein sources for mud crab ( Scylla paramamosain ), comprising Peruvian anchovy meal (PAM), local anchovy meal (LAM), Pacific mackerel meal (PMM), Antarctic krill meal (AKM), Pacific krill meal (PKM), and poultry by-product meal (PBM), to provide practical guidance for developing balanced diet formulations in crustacean aquaculture. Experimental diets were formulated by combining 70 % reference diet with 30 % test protein sources, and supplemented with 0.5 % chromium oxide as an inert marker. Mud crabs (32.80 ± 0.68 g) were randomly allocated to 210 individual plastic rearing boxes, with three replicates per treatment (10 crabs per replicate). The ADCs of dry matter and protein for all protein sources were varying from 70.33 % to 83.71 % and 80.91–89.37 %, indicating favorable overall digestibility. By comparison, the ADCs of crude lipid and phosphorus ranged from 71.15 % to 88.37 % and 64.72–99.91 %, respectively. AKM and PKM exhibited significantly higher ADCs for crude protein and phosphorus, whereas PBM showed the lowest values for these two indicators. Moreover, PMM exhibited the highest lipid ADCs. Amino acid ADCs followed a similar trend to crude protein, with total amino acid ADCs ranging from 87.62 % to 91.20 %, in which AKM and PKM showed superior digestibility for most amino acids except for alanine and cysteine. Chemical score (CS) and essential amino acid index (EAAI) indicated that AKM, PKM, and PMM had more balanced amino acid profiles, whereas PBM showed lower protein quality. Overall, the results indicate that AKM, PKM, and PMM are balanced protein sources with superior digestibility for S. paramamosain .