Plant protein contains anti-nutritional factors and amino acid imbalance, excessive addition can lead to the decline of aquatic animal growth performance, low immunity. The results showed that the growth performance of rainbow trout, salmon and flounder decreased and the feed coefficient increased when the dietary plant protein content was more than 20%-30%.
When the replacement of fish meal by cottonseed meal exceeds 30%, turbot, rainbow trout, Atlantic salmon and channel catfish are affected by the presence of anti-nutritive factor mustard oil Compared with fish meal, plant protein lacks lysine, methionine and other limiting amino acids, resulting in unbalanced amino acid nutrition, which leads to the "barrel effect" of amino acids affecting growth performance (carnivorous fish are more sensitive to limiting amino acids, and the higher the substitution level, the worse the absorption).
The diets were fed for 8 weeks with different contents of Clostridium butyricum in low fish meal diets, which were labeled as C1 (3×10⁸ CFU /kg), C2 (1.2×10⁹ CFU /kg), C3 (4.8×10⁹ CFU /kg) and C4 (1.92×10¹⁰ CFU /kg) groups. The growth performance, intestinal digestive enzymes, serum biochemical indexes, serum antioxidant capacity and serum non-specific immune indexes of Penaeus vannamei were evaluated.

With the increase of Clostridium butyricum  supplemental level, the weight gain rate and specific growth rate of Penaeus vannamei generally increased first and then decreased.

With the increase of Clostridium butyricum supplemental level, the activities of amylase (AMS), lipase (LIP) and trypsin (TRY) in the intestinal tract of shrimp showed an increasing trend.

The contents of serum triglyceride (TG), total cholesterol (T-CHO), high density lipoprotein (HDL) and low density lipoprotein (LDL) in the experimental group were significantly lower than those in the PC and NC groups.

With the increase of Clostridium butyricum supplemental level, serum total antioxidant capacity (T-AOC), superoxide dismutase (SOD) and glutathione peroxidase (GPX) activities showed an increasing trend, while malondialdehyde (MDA) content showed a decreasing trend.

Lysozyme (LMZ) showed an increasing trend with the increase of Clostridium butyricum supplemental level. Alanine aminotransferase (GPT) in C4 group was significantly higher than that in other groups. The mean value of glutamic-oxalacetic transaminase (GOT) in C4 group was the lowest, which was significantly lower than that in C1 and C2 groups. Alkaline phosphatase (AKP) in C2 group increased first and then decreased, which was significantly higher than that in other groups. The average value of acid phosphatase (ACP) in C3 group was the highest, which was significantly higher than that in NC and PC groups.
In conclusion, low fish meal diet supplemented with Clostridium butyricum can significantly improve the antioxidant capacity, intestinal digestive enzyme capacity and non-specific immune ability of Penaeus vannamei.