Investigating the effect of different amounts of soybean meal (Glycine max) containing Phyzyme® XP enzyme on the hematological indicators and activity of serum liver enzymes of Caspian trout (Salmo caspius Kessler, 1877)

This study was conducted to examine the effect of diets containing various amounts of soybean meal and Phyzyme^® XP on hematological indicators and serum liver enzymes in Caspian trout (Salmo caspius) with the average weight of 148.1±1.98 g for 85 days. For this purpose, 240 pieces of juvenile Caspian trout were randomly distributed in six treatments, including control treatment (basic diet) and five experimental treatments including  treatment I (basic diet + 2000 IU/kg diet of Phyzyme^® XP), treatment II (basic diet containing 20% soybean meal), treatment III (basic diet containing 20% soybean meal + 2000 IU/kg diet of Phyzyme^® XP), treatment IV (basic diet containing 40% soybean meal), and treatment V (basic diet containing 40% soybean meal + 2000 IU/kg diet of Phyzyme^® XP) with two repetitions per treatment (20 pieces of fish per repetition). The largest amounts of red blood cells and hematocrit were observed in treatments I and III, respectively, which was significantly different only from treatment IV (p<0.05). The largest amount of hemoglobin was observed in the control treatment, which was significantly different from other treatments, except treatment I (p<0.05). The highest number of white blood cells was observed in treatment III, which was significantly different from other treatments (p<0.05). The lowest serum levels of the liver enzymes, including lactate dehydrogenase and alkaline phosphatase, were recorded in treatment I and control treatment, respectively, which showed no significant difference from treatments II and III (p>0.05). Besides, serum levels of these enzymes in treatment V showed no significant difference from treatments II and III (p>0.05). Therefore, according to the results of the present study and no significant differences in the values of most of the parameters between the control treatment and treatment V, it is recommended to replace 40% soybean meal containing 2000 IU/kg diet of Phyzyme^® XP, instead of fish meal, in order to achieve an affordable diet without any negative impact on health parameters in the Caspian trout.