Partial fishmeal protein replacement with peptides from swine blood modulates the nutritional status, immune response, and intestinal microbiota of hybrid groupers (female Epinephelus fuscoguttatus× male E. lanceolatus)

This study investigated the effects of replacing fish meal (FM) protein with peptides from swine blood (PSB) on the growth, digestion, and absorption capacity of hybrid groupers (female Epinephelus fuscoguttatus × male Epinephelus lanceolatus). It also analyzed their inflammatory-related gene expression, and intestinal microbiota. Four isonitrogenous and isolipidic experimental feeds were formulated to replace 0% (FM), 25% (PSB25), 50% (PSB50), and 75% (PSB75) of the FM protein with PSB. Each experimental diet was fed to triplicate groups of 30 hybrid grouper juveniles for 8 weeks. No significant differences in the weight gain and specific growth rates were found among the FM, PSB25, and PSB50 groups. The intestinal digestive enzyme (lipase, amylase, trypsin, and pepsin) and brush border enzyme (Na+/K+-ATPase, creatine kinase, and γ-glutamyl transpeptidase) activities showed no significant differences among the FM, PSB25, and PSB50 groups. Meanwhile, trypsin, pepsin. Creatine kinase, and γ-glutamyl transpeptidase activities in the PSB group were significantly higher than those of the FM group. No significant differences in the expression levels of the toll-like receptor 21 (TLR21), myeloid differentiation factor 88 (MyD88), and inflammatory cytokines (TNF-α, IL-2, IL-8, and IL-10) were observed among the four groups. The intestinal microbiota results showed no significant differences in alpha diversity among the four groups. At the genus level, at the genus level, Lactobacillus relative abundance was significantly reduced in the PSB10 group compared to that in the FM group. However, no significant differences were found among the FM, PSB50, and PSB75 groups. However, no significant differences were found among the FM, PSB50, and PSB75 groups. These results demonstrated that up to 50% of the FM protein in the feed can be replaced by PSB without adversely affecting the nutritional status and inflammatory response in hybrid groupers. Replacing FM with PSB significantly influences the microbial profile but not the diversity •Substitution of fishmeal (FM) up to 50% with peptides from swine blood (PSB) can be replaced by PSB without adverse effects on the nutritional status and inflammatory response.•PSB has a significant influence on microbial profiles but not on diversity.•PSB could be a cost-effective alternative to FM in feed for hybrid groupers.