The worldwide increase in aquaculture production and the decrease of wild fish stocks has made the replacement of fish oil (FO) in aquafeed industry a priority. Therefore, the use of terrestrial animal fats and vegetable oils, which has lower cost and larger supplies, may be good as substitute for FO. This study investigate the effects of total replacement of FO by two terrestrial animal fats (pork lard and poultry fat) and three vegetable oils (palm kernel oil, sheabutter oil and sunflower oil) on haematological and serum biochemical profile of Heterobranchus longifilis over 70 days. FO-diet was used as the control. The haematological parameters were significantly affected by dietary lipid sources. Serum total protein was not influenced by the dietary lipids. However, serum cholesterol was significantly higher in fish fed diet containing sunflower oil. Glucose and activities of liver enzymes in blood serum were significantly reduced in fish fed alternative lipids when compared with the control. These results indicate that FO can be replaced completely with alternative lipids without any serious negative health impacts.
Castor seed variously treated by boiling, roasting, boiling and roasting, decorticated lyle treated, boiling and fermenting was tested for improved nutrient content and elimination of toxins. 10% processed castor seed cake (CSC) was included in diets and fed to 180 catfishes for 4-weeks to assay the dietary castor seed based on performance and some biochemical indices. Processing methods other than boiling improved performance and other measured parameters and some diets containing treated CSC produced results even better than that obtained on the conventional diet (p < 0.05). Dietary boiled CSC elicited low feed intake, body weight gain, poor feed efficiency and high mortality of the fed fish relative to the control diet (p < 0.05). Similarly, boiled CSC in diet gave poor results on biological values of specific growth rate, net protein utilization, nitrogen metabolism, protein efficiency ratio compared to the control diet or diets containing CSC treated by methods other than boiling (p < 0.05). The best result was obtained on the diet containing castor seeds treated by boiling followed by roasting (p < 0.05). For optimum utilization of CSC in nutrition of fish, it has to be boiled and roasted.
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