In this study, the effect of different levels of Bio-Aqua probiotic supplement on the qualitative indices of grass carp, Ctenopharyngodon idella, as well as non-biological and biological parameters of earthen ponds was investigated. For this purpose, fish with an average initial weight of 2.0 ± 0.1 g were selected for 120 days. In the present study, treatments including 0 g/ha (control), 250 g/ha (treatment 1 = T1), 350 g/ha (treatment 2 = T2) and 450 g/ha (treatment 3 = T3) of this Bio-Aqua probiotic supplement were added to the ponds. Based on the results, the specific growth rate, daily growth rate, weight gain, and survival rate in T3 (450 g/ha) showed a significant difference compared to other treatments (p<0.05). Moreover, significant differences were found in the crude protein and moisture content of grass carp in T3 compared to the other treatments, especially the control group (p<0.05). In addition, there was a significant difference in lymphocytes, neutrophils, monocytes, hemoglobin, hematocrit, white and red blood cells count in T3 compared to the other treatments (p<0.05). Bio-Aqua probiotic supplement from 450 g Bio-Aqua /ha (in T3) caused a significant reduction in TSS, BOD, COD, nitrite, and phosphate levels of water compared to the other experimental treatments (p<0.05). In conclusion, Bio-Aqua probiotic supplementation, especially at T3 (450 g/ha) exhibited improved growth performance, nutritional value, survival rate, chemical composition, and hematological parameters in grass carp.
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