Effects of dietary oak (Quercus aegilops L.) acorn on growth performance, somatic indices, and hemato-biochemical responses of common carp, Cyprinus carpio L., at different stocking densities

ABSTRACT The present study was done to assess the effects of dietary oak (Quercus aegilops L.) acorn powder (OAP) on the growth performance, somatic indices, and hemato-biochemical responses of common carp, Cyprinus carpio L., reared at different stocking density conditions. For this purpose, fish (~55 g) were distributed into sixteen 70-L tanks at a density of 3 g/L (LSD) or 10 g/L (HSD) and fed diets supplemented with 0.0 (control) or 10 g OAP/kg for 6 weeks. The results showed significant increase in the performance of fish fed with the OAP additive at both stocking densities, but it was retarded at the control-HSD level. Fulton’s condition (K) factor as well as hepatic, gonads, and kidney somatic indices remained constant after the experimental period, but viscera and spleen somatic indices were significantly (P < 0.05) affected by dietary OAP and stocking density. The dietary OAP caused significant increases in counts of white blood cells and red blood cells as well as hemoglobin and hematocrit values in LSD conditions, while the control-HSD fish showed their lowest values. Additionally, the dietary OAP and stocking density were significantly modulated by the biochemical variables. In the control-HSD fish, higher glucose levels accompanied with lower levels of total protein, albumin, and globulin were observed. Fish reared under the control-HSD conditions showed highest levels of aspartate and alanine aminotransferases, creatinine, and uric acid, while their lowest values were recorded with the OAP-LSD fish. The control-HSD fish had highest levels of total cholesterol and triglycerides among the experimental groups. The dietary supplementation of OAP to the fish in HSD conditions induced significant (P < 0.05) decreases in total cholesterol and triglycerides than the control-HSD fish group, and their lowest levels were obtained at the OAP-LSD fish. Levels of low-density lipoprotein cholesterol (LDL) and high-density lipoprotein cholesterol (HDL) were significantly (P > 0.05) modulated by dietary OAP and stocking density. The highest level of LDL was recorded in the control fish at both densities, while the highest level of HDL was obtained in the control-LSD fish. The dietary supplementation of OAP enhanced the hemato-biochemical parameters of the control fish at HSD conditions to be similar to the control-LSD fish. In conclusion, a dietary level of 10 g OAP/kg diet was confirmed as a natural feed additive to improve aquaculture and welfare of common carp, especially under high stocking density conditions.