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The present study evaluated the enhancement of the growth rate, intestinal health, immune-related genes, and resistance against suboptimal water temperature in common carp (2.01 ± 0.02 g) by dietary paraprobiotics. Fish were fed dietary heat killed Lactobacillus plantarum (LP20) at 0 (control), 50, and 100 mg/kg for 2 months. After the feeding trial fish were exposed to suboptimal water temperature averaged 13.22 ± 0.44 °C for 48 h. The final body weight, weight gain, specific growth rate, and feed conversion ratio of fish fed LP20 at 100 mg/kg were significantly enhanced (P < 0.05). The villi length and width were increased in fish fed LP20 at 50 and 100 mg/kg when compared to the control (P < 0.05). The crypt depth was increased by increasing LP20 in a dose dependent manner with the highest value in the group of fish fed 100 mg/kg (P < 0.05). The number of goblet cells showed higher number in fish fed LP20 at 50 and 100 mg/kg than the control group (P < 0.05). The expression of catalase (CAT) gene did not show any changes in transcription before the thermal stress however after thermal stress fish fed 50 mg/kg had upregulated CAT followed by those fed 100 mg/kg. Glutathione peroxidase (GPx) and superoxide dismutase (SOD) gene expressions showed upregulations in fish fed 50 mg/kg before the thermal stress but after the thermal stress fish fed 100 mg/kg had the highest level of mRNA transcriptions for GPx and SOD genes. In the same manner, the expression of interleukin 1β (IL-1β), tumor necrosis factor α (TNF-α), and interleukin 10 (IL-10) were significantly upregulated in fish fed LP20 at 50 mg/kg before the thermal stress whereas the expression of these genes was upregulated in fish fed 100 mg/kg. In conclusion, using LP20 at 50−100 mg/kg resulted in enhancing the growth rate, intestinal morphometry, immune and antioxidative related genes. Accordingly, common carp showed high resistance against suboptimal water temperature stress.

The present study evaluated the possible synergistic impacts of sodium butyrate and Spirulina platensis as a feed additive on growth performance, carcass composition, blood health, and intestinal histomorphology of Nile tilapia (Oreochromis niloticus). A control and three treated diets were supplemented with sodium butyrate (SB) 350 mg, Spirulina platensis (SP) 1g and a mixture of 350 mg SB and 1g SP/kg diet (SB/SP) respectively, were fed for monosex Nile tilapia (12.5± 0.50 g, n=120) for two months. The results revealed higher growth performance (final weight, weight gain, weight gain rate, SGR and PER) compared to control group (CG) (P