Effects of dietary co-exposure to fungal and herbal functional feed additives on immune parameters and microbial intestinal diversity in rainbow trout (Oncorhynchus mykiss)

Ameliorating effects of natural herbal supplements against water-borne induced toxicity of heavy metals on Nile tilapia, (Oreochromis niloticus)

The efficacy of herbal supplements in mitigating heavy metals (HMs) toxicity was investigated using a widely grown fish, the Nile tilapia (Oreochromis niloticus). The experiment was conducted over two phases: during the stress phase, the experimental fishes were exposed to sub-lethal concentrations of HMs, including lead, cadmium, zinc, and copper for 15 days; following which during the feeding phase, herbal supplements were given for 70 days to ameliorate their effects. Seven groups were established: the control negative group (CON-ve), control positive group (CON+ve, without any treatment), and five groups with supplementation of 1% turmeric (TUR), cinnamon (CIN), ginger (GIN), garlic (GAR), and their mixture (MIX), respectively. A total of 315 fishes were distributed evenly in experimental tanks (15 fishes per tank, in triplicates). The results revealed that exposure to HMs led to significant (p < 0.05) alterations in all the tested parameters, i.e., liver damage and growth reduction. The herbal supplements, especially the MIX groups, ameliorated the harmful effects of HMs and restored fish growth, digestibility, carcass composition, and liver health. In conclusion, the study demonstrated that the herbal supplements were effective in reducing the HMs-linked toxicity in Nile tilapia. Future studies pertaining to the mechanisms facilitated by the various herbal bioactive substances-linked tolerance to HMs in fishes are warranted.

Effect of dietary intervention with Capsicum annuum extract on growth performance, physiological status, innate immune response, and related gene expression in Nile tilapia

The red pepper (Capsicum annuum) has gained great attention recently because of its biological and pharmacological characteristics. The present approach aimed to evaluate the effects of C. annuum alcoholic extract (CAE) supplementation on Nile tilapia (Oreochromis niloticus) growth performance, physiological status, some metabolic, immune, and regulatory genes expression, and resistance against Streptococcus agalactiae infection. Fish (22.26 ± 0.19 g) were assigned to four treatments (five replicates, each with 10 fish replicate-1) and fed tested diets for 60 days. The experimental diets were supplemented with CAE at 0, 0.4, 0.8, and 1.6 g kg-1, expressed as CAE0, CAE0.4, CAE0.8, and CAE1.6, respectively. The findings exhibited that CAE dietary supplementation improved growth performance, feed utilization, elevated growth hormone level, and digestive enzyme activities (amylase and protease), and lowered leptin hormone in a level-dependent manner. Boosting the mRNA expression of the transporter proteins (solute carrier family 15 member 2 and solute carrier family 26 member 6) and insulin-like growth factor-1 genes with a decrease in the myostatin gene expression was noticed in the CAE-fed groups. The innate immune (serum bactericidal activity %, complement 3, and phagocytic activity %) and antioxidant (glutathione peroxidase and total antioxidant capacity) parameters were significantly (p < 0.05) improved, and the serum malondialdehyde level was significantly decreased by CAE dietary inclusion. A marked upregulation in the mRNA expression of interleukins (il-1β, il-6, il-8, and il-10), transforming growth factor-β, glutathione peroxidase, and glutathione synthetase genes were observed in CAE-fed groups. Dietary CAE decreased the cumulative mortalities after the challenge with S. agalactiae by 20, 13.33, and 10% in CAE0.4, CAE0.8, and CAE1.6, respectively, compared to the control (40%). Overall, dietary supplementation with CAE could improve growth performance and physiological status, and modulate the expression of several regulatory genes in Nile tilapia. The recommended level of CAE is 1.6 g kg-1 to augment growth and health status.

Effect of dietary koumine on the immune and antioxidant status of carp (Cyprinus carpio) after Aeromonas hydrophila infection

Koumine (KM) has anxiolytic, anti-inflammatory and growth-promoting effects in pigs and sheep. Based on the growth-promoting and immunological effects of koumine, the present study was conducted on Cyprinus carpio (C. carpio) with four KM concentrations: 0 mg/kg, 0.2 mg/kg, 2 mg/kg, and 20 mg/kg for 10 weeks, followed by a 1-week Aeromonas hydrophila (A. hydrophila) infection experiment. The effect of KM on the immunity of A. hydrophila infected carp was analyzed by histopathology, biochemical assay, and qRT-PCR to assess the feasibility of KM in aquaculture. The results showed that the presence of KM alleviated pathogen damage to carp tissues. At 2 mg/kg and 20 mg/kg concentrations of KM successively and significantly elevated (p < 0.05) the SOD activities in the intestinal tract, hepatopancreas and kidney of carp. The expression levels of hepatopancreatic antioxidant genes Nrf2 and IGF-1 were significantly up-regulated in the same group (p < 0.05), while the expression levels of immune genes IL-8 and IL-10 were down-regulated. In summary, KM at concentrations of 2 mg/kg and 20 mg/kg could regulate the expression of antioxidant and immune genes in various tissues in an orderly and rapid manner, and significantly improve the antioxidant and immune abilities of carp, which is conducive to the improvement of the resilience of carp.