Comparative study on the utilization of four forms exogenous methionine by red swamp crayfish (Procambarus clarkii)

To investigate the efficacy of four forms of methionine (Met) supplementation in red swamp crayfish (Procambarus clarkii), a Met-deficient all-plant protein diet was used control, along with four supplemental diets: 0.90 g/kg Met-Met, 1.80 g/kg crystal DL-Met, 3.60 g/kg E-Met, and 3.29 g/kg MHA-Ca. The analysis Met + Cys levels of five diets were 10.46 (control), 11.51, 12.50, 12.56, and 10.70 g/kg, respectively. Each diet was hand-fed to five replicates of 18 crayfish each (initial body weight: 4.40 +/- 0.02 g) for eight weeks. Supplementation with four forms of exogenous Met resulted in an increase in weight gain rate, specific growth rate, and antioxidant capacity, while decreasing the feed conversion ratio (P < 0.05). The abdominal muscle crude protein content and the protein deposition rate in the Met-Met and E-Met groups were higher than those of the control group (P < 0.05). The deposition rate of Met, arginine, leucine, lysine, threonine, and valine, and the activities of digestive enzymes were higher in the Met-Met group than that of the control group (P < 0.05). The peak times and values of serum biochemical indices were affected by four forms of exogenous Met. Additionally, the hepatopancreatic homocysteine content in the MHA-Ca group was higher than in the control group (P < 0.05). In conclusion, the utilization of Met-Met by Procambarus clarkii was superior to other forms of Met in an all-plant protein diet.