Influence of dietary phosphorus levels on growth,body composition,metabolic response and antioxidant capacity of juvenile snakehead (Channa argus × Channa maculata) |
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| Authors: | H‐M Shen X‐R Chen W‐Y Chen S‐M Lin Y‐J Chen L Zhang L Luo |
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| Affiliation: | 1. College of Animal Science and Technology, Southwest University, Chongqing, China;2. Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Southwest University, Chongqing, China;3. Tongwei Co., Ltd., Special Fisheries Research Institute, Chengdu, China |
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| Abstract: | A study was conducted to estimate the optimum requirement of dietary phosphorus (P) for Channa argus × Channa maculata. Effects of dietary P levels on the tissue composition, serum biochemical parameters and antioxidant status were also examined. Five practical diets were formulated to contain graded levels (4.8 g kg?1, 6.4 g kg?1, 7.9 g kg?1, 9.4 g kg?1 and 11.0 g kg?1) of available P from dietary ingredients and monocalcium phosphate (MCP). Each diet was randomly assigned to triplicate groups of 30 juvenile fish (initial body weight, 20.50 ± 0.53 g) for 8 weeks. The results showed that the specific growth rate (SGR) and weight gain (WG) were all significantly improved by dietary P up to 9.4 g kg?1 (P < 0.05) and then levelled off beyond this level. Broken‐line analysis showed maximum weight gain (WG) was obtained at dietary available P concentrations of 9.6 g kg?1. With the increase in dietary P level, protein efficiency rate (PER) increased significantly and reached a plateau, while the feed conversion ratio (FCR), the mesenteric lipid somatic index (MSI) and the whole‐body lipid content significantly reduced (P < 0.05). Dietary P levels also affected the mineralization (ash and P) of whole body, vertebrae and scale (P < 0.05). Quadratic analysis based on P contents in whole body, vertebrae, scale and ash content in vertebra indicated that the available P requirements were 10.4, 9.8, 10.0 and 10.3 g kg?1, respectively. However, no differences were found in the whole‐body moisture, crude protein, serum calcium (Ca) contents or Ca/P value, as well as the viscerosomatic index (VSI) and hepatosomatic index (HSI) among all the treatments (P > 0.05). Triglyceride (TG), total cholesterol (TC), high‐density lipoprotein cholesterol (HDL‐C) and low‐density lipoprotein cholesterol (LDL‐C) decreased significantly, while serum P content, HDL‐C/TC and HDL‐C/LDL‐C value increased significantly with dietary available P levels (P < 0.05). No significant changes in superoxide dismutase activity and malondialdehyde (MDA) content were observed (P > 0.05), but serum catalase (CAT) and glutathione peroxidase (GPx) activities and the ratio of CAT/SOD and GPx/SOD increased significantly with increasing dietary P levels (P < 0.05). In conclusion, the optimal P requirement of juvenile snakehead in practical feed was 9.6 g kg?1. Signs of P deficiency were characterized by poor growth, slightly reduced mineralization and the antioxidant capacity and an increase in body lipid content. |
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| Keywords: | antioxidant capacity
Channa argus × Channa maculata
nutrition phosphorus |
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