The study investigated the alleviated effects of Alpha-ketoglutaric acid (AKG) on the intestinal health of mirror carp (Cyprinus carpio Songpu) caused by soy antigenic protein. The dietswere formulated from fishmeal (CON),50% soybean meal (SBM),the mixture of glycinin and β-conglycinin (11+7S) and adding 1% AKG in the 11+7S (AKG). Carp (~4 g) in triplicate (30 fish per tank) was fed to apparent satiation thrice a day for six weeks. Compared with CON, SBM treatment resulted in significantly poor growth performance (P<0.05), whereas 11+7S and AKG treatments were not significantly different from CON (P>0.05). Gene expression of tumor necrosis factor (TNF-α) and interleukin-1 β (IL-1β) in proximal intestines (PI) and distal intestines (DI) were increased (P<0.05), and transforming growth factor (TGF-β) in PI and middle intestines (MI) was decreased (P<0.05) in both SBM and 11+7S. The gene expression of caspase-3 in DI increased in SBM (P<0.05) and the caspase-3 and caspase-9 in DI increased in 11+7S (P<0.05); conversely, the gene expression of TGF-β in PI and MI was increased, TNF-α and IL-1β in the MI, caspase-3, and caspase-9 in DI was decreased in AKG (P<0.05). mRNA levels of TOR in PI and MI, ACC in PI, MI and DI was decreased in SBM (P<0.05), the mRNA levels of AMPK in the PI and DI, TOR in PI, MI and DI, ACC in PI and DI, 4E-BP in DI was reduced in 11+7S (P<0.05). AMPK in the PI and DI, ACC in the PI and MI, TOR PI, MI, and DI, 4E-BP in PI and DI was recovered by AKG supplementation (P<0.05). Lipids and lipid-like metabolism, organic acids and derivatives metabolism increased in AKG dietary treatment. In conclusion, AKG reduces the expression of intestinal inflammation and apoptosis pathway and changes glycerophospholipid metabolism and sphingolipid metabolism in the intestine of fish.

A 56-day feeding trial was performed to determine the effect of replacing fishmeal with 0, 25%, 50%, 75%, and 100% PBM (FM) on growth performance, digestive enzyme, and immunity of juvenile giant river prawn (Macrobrachium rosenbergii). Diets were fed in quadruplicate (50 prawns per replicate) to satiation (3–5% of their body weight). The finial weight, weight gain, and specific growth rate of prawns were significantly reduced P < 0.05 when 100% PBM was substituted for fish meal, whereas the remaining test diets showed no variation compared to the control P > 0.05 . There was no significant difference in survival rates. The moisture, crude protein, and crude fat of the prawn were unchanged P > 0.05 . The SOD activity, MDA content, and AKP activity of hemolymph did not change significantly. However, the ACP activity of all replacement groups decreased significantly P < 0.05 . The amylase enzyme activity in the intestine of prawn fed 25% of PBM increased significantly compared with the control group, while the trypsin and lipase activities were unchanged. This study showed that PBM up to 75% replacement group does not affect growth performance, and all replacement groups have no adverse effect on intestinal digestive enzyme activity and immunity in juvenile M. rosenbergii. Therefore, poultry by-product meal could replace fish meal by up to 75%.