The synergistic effects of BetaPlus® Ultra and prebiotic oligosaccharides on growth performance, hepatosomatic index, hematological parameters, and carcass quality of Caspian trout (Salmo caspius)

The present study aimed to investigate the effect of the commercial probiotic BetaPlus® Ultra (BP Ultra) in combination with the galacto-oligosaccharide (GOS) or the isomalto-oligosaccharide (IMO) prebiotics in Caspian trout (Salmo caspius) parr. S. caspius (8.5±0.07 g) was randomly distributed in three dietary treatments including: control group, synbiotic treatment I (0.1% BP Ultra + 0.2% GOS) and synbiotic treatment II (0.1% BP Ultra + 0.2% IMO) and in nine 300 L circular polyethylene tanks with three replications per treatment and, then, fed for seven weeks. At the end of this experiment, growth performance and hepatosomatic index improved significantly in both synbiotic treatments compared to the control group (p<0.05). However, the trend of this improvement was more noticeable in the synbiotic treatment I compared to the synbiotic treatment II without any significant difference (p>0.05). The counts of red and white blood cells in the both synbiotic treatments were significantly decreased and increased compared to the control group, respectively (P<0.05). The values of hemoglobin, packed cell volume, and mean corpuscular hemoglobin in the synbiotic treatment I showed significant increases compared to the synbiotic treatment II (P<0.05). The highest significant levels of crude protein and lipid in carcass were observed in the synbiotic treatment II and the synbiotic treatment I, respectively (P<0.05). Dry matter of carcass was increased significantly in the synbiotic treatment I compared to the synbiotic treatment II (P<0.05). The lowest ash content of carcass was observed in the synbiotic treatment I with a significant difference compared to the synbiotic treatment II and the control group (P<0.05). The results of the present study demonstrated the remarkable efficiency of the synbiotic treatment II on the protein increase and lipid reduction in carcass, although the synbiotic treatment I had a better effect on growth performance and hematological parameters in S. caspius.