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The purpose of this study was to investigate the effects of inactivated Lactobacillus plantarum and its metabolite (LPM) on the growth performance and intestinal health of Procambarus clarkii. A total of 162 Procambarus clarkii with an initial weight of (8.16±0.23) g were randomly divided into three groups with three replicates in each group and 18 shrimps in each replicate. Three groups of compound diets containing 0 (control group), 300 (LPM-300 group), 600 mg/kg (LPM-600 group) of Lactobacillus plantarum and its metabolite (LPM) were prepared. In the two experimental groups, 3% flour was used instead of 3% peanut meal on the basis of the feed formula of the control group, which reduced the protein level of the feed by 1.5%. The trial period was 42 days. The results showed that the weight gain rate, specific growth rate, protein efficiency and protein deposition rate of Procambarus clarkii were significantly higher than those of the control group (P<0.05), while the feed coefficient was significantly lower than that of the control group when 600 mg/kg LPM was added to the diet (P<0.05). The contentations of crude protein, crude fat and crude ash of whole shrimp fed with 600 mg/kg LPM were significantly higher than that of the control group (P<0.05). When 300 and 600 mg/kg LPM was added to the diet, the crude fat content of muscle was significantly higher than that of the control group (P<0.05). Compared with the control group, the content of serum total protein (TP) increased significantly (P<0.05), and the activities of aspartateoxaloacetic transaminase (AST) and alanine-pyruvic transaminase (ALT) decreased when LPM was added to the diet (P<0.05). The content of serum albumin (ALB) and the activity of alkaline phosphatase (AKP) were significantly increased when 600 mg/kg LPM was added to the diet (P<0.05). The protease activity of hepatopancreas and intestinal tract was significantly increased by adding 600 mg/kg LPM (P<0.05). The addition of 600 mg/kg LPM significantly reduced the villus width of the shrimp compared with the control group (P<0.05). The hepatopancreas cells in the control group and the experimental group were intact without damage or pathological changes. The number of B cells, F cells, and R cells in the LPM-300 group was significantly more than that in the control group. The study indicates that the addition of 600 mg/kg LPM in the feed can improve the intestinal tissue structure of Procambarus clarkii, enhance the non-specific immunity and promote the utilization of feed protein. [ABSTRACT FROM AUTHOR]

In the present study, we obtained the full-length cDNA sequences of TLR21 and TLR22 from Nile tilapia ( Oreochromis niloticus) ( On TLR21 and On TLR22, respectively). The gene structure and expression patterns of On TLR21 and On TLR22 were also studied in order to understand the function of these genes in tilapia immunity. The On TLR21 gene was 3196 bp in length, with an open reading frame ( ORF) of 2940 bp encoding 979 amino acid residues and with no introns. The On TLR22 gene contained three exons and two introns, with an ORF of 2886 bp, encoding 961 amino acid residues. The TLR family motifs, that is leucine-rich repeat ( LRR) domains and Toll/interleukin ( IL)-1 receptor ( TIR) domains, are conserved in the putative On TLR21 and On TLR22 proteins. Quantitative real-time PCR ( qRT- PCR) analysis revealed the presence of the On TLR21 transcript in 10 tissues of healthy fish, with the highest expression level in the gill and the lowest expression level in the liver. In contrast, the highest expression level of On TLR22 was detected in the spleen, while the lowest expression level was in the liver. The expression pattern of TLR during embryonic development showed that the expression levels of On TLR21 significantly increased from 2.5 to 6.5 days post fertilization (dpf), decreased at 7.5 dpf and increased at 8.5 dpf. While the expression levels of On TLR22 significantly decreased from 3.5 dpf, and there were no significant differences from 3.5 to 8.5 dpf. Upon stimulation with an intraperitoneal injection of Streptococcus agalactiae, the expression levels of On TLR21 and On TLR22 were downregulated in the spleen, kidney and gill. These results may indicate that On TLR21 and On TLR22 play important roles in mediating the response protection against S. agalactiae in Nile tilapia. [ABSTRACT FROM AUTHOR]