Assessment of the effect of temperature on the carp physiology (Cyprinus carpio, L., 1758) fed with probiotics in condition of a recirculating aquaculture system

In order to establish the effect of temperature on the physiology of the carp, special attention was awarded to leukograma and absolute number of leukocytes of carp blood. Body's reaction to stress factors action involves physiological changes, including changes in blood composition and immune mechanisms. The hematological analysis has been effectuated in the experiment that took place during 60 days, in four breeding units of 500 litters in volume each. Four kinds of variants were compared: V1-pellets with 30% crude protein, without probiotics; V2-pellets with 30% crude protein, with probiotics of 2.24×109 CFU/kg food; V3-pellets with 30% crude protein, with probiotics of 3.84×109 CFU/kg food; and V4-pellets with 30% crude protein, with probiotics of 7.04×109 CFU/kg food. We used BioPlus®2B probiotics (a mixture of Bacillus licheniformis (DSM 5749) and Bacillus subtilis (DSM 5750). The microscopic examination of blood smears, which were coloured with May-Grunewald Giemsa panoptic method (both at the beginning and at the end of each experimental stage), we found that lymphocytes were predominant in comparison with other types of leukocytes, the absolute number being: V1 73.3 – 85.9%; V2 65.3 – 84.7%; V3 67.0 – 87.5%; V4 71.3 – 88.3%. It was noticed that eosinophilic granulocytes and basophils from the fish blood, were presented in a low number (0.1–0.8%), (0.2 – 0.4%) respectively, also at the beginning of the experiment and in the end of the two phases. The glucose concentration in blood registered higher values, across to normal values reported by literature for carp, also in control group (V1 – 101.8 mg/dl) as well as variants with different concentrations of probiotic (V2 – 104.6 mg/dl, V3 – 102.2 mg/dl, V4 – 116.2 mg/dl). The mean values of protein level were in the normal limits for carp, between 3.9 g/dl and 4.9 g/dl, aspect which suggests that fish present a normal physiological condition. In conclusion, probiotics can be used for enhancing the immune system and fish health, improving disease resistance of biological material