No abstract

The objective of the present study was carried out to evaluate partial and total replacing of the fishmeal protein supplied by sand smelt fishmeal (SSFM) (Atherina boyeri) in practical diets on fish health, growth performance and feed utilization of mono sex Nile tilapia (Oreochromis niloticus) fingerlings. The experiment lasted 16 weeks and includes five treatments 0, 25, 50, 75 and 100% sand smelt fish meal (SSFM), respectively. An experimental diet containing is onitrogenous diets (30% crude protein), Ten ponds includes five treatments (Two replicates-almost 4 m 3 /pond) and Nile tilapia fingerlings stocked in 25 fish/m 3 (7.65±0.3 g at initial body weight). The highest weight gain WG (75.94 g) was recorded for fish fed the 25% replacing diet (SSM25) followed by those fed the diet SSM50 (75.24 g), SSM75 (74.26 g), SSM0 (73.16 g) and SSM100 (72.14g), respectively and the differences in weight gain among the different fry groups were significant (P<0.05) and the same trend was observed for specific growth rate SGR. The average feed intake and feed conversion ratio and protein efficiency ratio of Nile tilapia were significantly (P<0.05) affected by the incorporation of sand smelt fish meal as a substitute of fish meal. Dry mater in whole fish body ranged between 28.83 and 29.59 with insignificant differences. Crude protein ranged between 55.69 and 58.06, ether extract ranged between 25.16 and 28.67, ash ranged between 14.83 and 15.58 with significant differences for ether extract and protein content of whole fish bodies. The present study indicated that replacing up to 75% of FM by SSM higher affected growth and feed utilization and reduced feeding costs by 13.99% for Nile tilapia (Oreochromis niloticus) fingerlings compared with control. Also, The results showed he can use sand smelt meal as an alternative to fish meal (Herring meal) at a rate of 100% in diets fed Nile tilapia without effect on the growth of total production compared to the control, which leads to higher economic returns.

The study was aimed at investigating the effects of Bacillus velezensis LSG2-5 isolated from host’s intestinal tract on growth performance, immune response, antioxidant capacity, and disease resistance of Amur minnow (Rhynchocypris lagowskii Dybowski). 535 fish were divided into 5 groups with 3 replicates per group. Diets containing different doses (0, 106, 107, 108, and 109 CFU/g, respectively) of B. velezensis LSG2-5 were used to feed fish ( 9.95 ± 0.05   g) for 56 days. Results showed that compared with control, weight gain rate and specific growth rate of fish were significantly increased by dietary 107-109 CFU/g B. velezensis ( p < .05 ). While for the feed conversion ratio, all treatment groups were significantly decreased ( p < .05 ). In serum, the contents of lysozyme and immunoglobulin M were significantly increased by dietary 106-109 CFU/g B. velezensis ( p < .05 ); the activities of component 3, component 4, and alkaline phosphatase were significantly increased by dietary 108 CFU/g B. velezensis ( p < .05 ). The activities of catalase, glutathione peroxidase, total antioxidant capacity, and superoxide dismutase in hepatopancreas were significantly increased by dietary 108-109 CFU/g B. velezensis ( p < .05 ). The activities of catalase, glutathione, glutathione peroxidase, total antioxidant capacity, and superoxide dismutase in the intestinal tract of 108 CFU/g group were significantly increased ( p < .05 ). However, malondialdehyde levels in the hepatopancreas and intestines were significantly decreased by dietary 107-108 CFU/g B. velezensis ( p < .05 ). Dietary 107-109 CFU/g B. velezensis significantly upregulated catalase, glutathione peroxidase, and copper/zinc superoxide dismutase mRNA levels ( p < .05 ). The levels of transforming growth factor β and interleukin-10 mRNA in the hepatopancreas of fish fed with B. velezensis of 108 CFU/g were significantly increased ( p < .05 ), and these in the intestinal tract of 106-109 CFU/g groups were upregulated ( p < .05 ). Feeding dietary 107-108 CFU/g B. velezensis significantly downregulated interleukin-8, interleukin-1β, and tumour necrosis factor α mRNA levels in hepatopancreas and intestines ( p < .05 ). After 56 days of feeding, 225 fish ( 23.20 ± 0.59   g) were challenged with Aeromonas hydrophila (108 CFU/g), and survival rates were recorded for the next 14 days. Meanwhile, the serum immune parameters of fish were determined. Results showed that compared with control, the survival rates of the treatment groups were significantly increased ( p < .05 ). Lysozyme, component 3, component 4, immunoglobulin M, acid phosphatase, and alkaline phosphatase levels in serum by dietary106-109 CFU/g B. velezensis showed significant promoting effects ( p < .05 ). In conclusion, dietary 107-109 CFU/g B. velezensis boosts the growth, immunity, antioxidant capacity, and against A. hydrophila infection of Amur minnow. Regression analysis suggested that the optimal dose of B. velezensis LSG2-5 in the Amur minnow diet was 5.00 × 10 8   CFU/g.

Probiotics are widely used in aquaculture. This article aims to study the effect of Bacillus amyloliquefaciens LSG2‐8 on the intestinal barrier function of Rhynchocypris lagowskii. B. amyloliquefaciens LSG2‐8 were added to R. lagowskii basal diets (CK) as additives at four concentrations: 1.0 × 106 (D‐6), 1.0 × 107 (D‐7), 1.0 × 108 (D‐8) and 1.0 × 109 (D‐9) CFU g−1 by dry weight of basal diet. After a 56‐day feeding experiment, the activities of intestinal digestive enzymes and immunity‐related enzymes of R. lagowskii on group D‐6, D‐7, D‐8 and D‐9 diet were significantly higher than the control (P < 0.05). In molecular experiments, the authors found that the levels of TGF‐β mRNA, IL‐10 mRNA, ZO‐1 mRNA and claudin‐3 mRNA in group D‐8 R. lagowskii were significantly higher (P < 0.05) than those of the control and other groups. Furthermore, the levels of IL‐1β and IL‐8 mRNA of R. lagowskii on group D‐6, D‐7, D‐8 and D‐9 diet were significantly lower than those of the control (P < 0.05). In addition, the authors found that B. amyloliquefaciens LSG2‐8 can regulate the intestinal flora balance and improve the intestinal structure of R. lagowskii. In conclusion, B. amyloliquefaciens LSG2‐8 can improve the intestinal barrier function of R. lagowskii and can be used as a feed additive in aquaculture.