Dietary lipid requirements of larval genetically improved farmed tilapia,Oreochromis niloticus (L.), and effects on growth performance,expression of digestive enzyme genes,and immune response |
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| Authors: | Hong Yang Yi‐Lan Sun Yi‐Fan Tao Pao Xu Zhi‐Xiang Zhu |
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| Affiliation: | Key Laboratory of Freshwater Fisheries and Germplasm Resources Utilization, Ministry of Agriculture, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi, Jiangsu, China |
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| Abstract: | The present study was performed to investigate the effects of dietary lipid level on growth performance, antioxidant defense, and mRNA levels of digestive enzymes and immune genes in larval genetically improved farmed tilapia (Oreochromis niloticus). The results show that larvae fed lipid levels of 4–11.5% had greater weight gain (WG), feed efficiency, protein efficiency ratio and survival than larvae fed the other dietary lipid levels (P < 0.05). No difference whole‐body crude protein, ash or moisture contents were found between treatments (P > 0.05) but lipid contents increased as dietary lipid level was increased. The 8% and 11.5% dietary lipid levels had stimulatory effects on trypsin mRNA level compared with those of larvae fed the 15% and 18.5% lipid diets. Intestinal and liver amylase mRNA levels decreased in larvae fed the 18.5% lipid diet, following the decrease in dietary starch. Analysis of the secondary curve equation for WG indicated that the optimal dietary lipid level in larval tilapia was 8.56%. In addition, the 4–11.5% lipid levels improved superoxide dismutase and glutathione peroxidase activities and increased mRNA levels of heat shock protein70, hepcidin antimicrobial peptide‐1, and C‐type lysozyme in the liver of larvae (P < 0.05). A 192‐h Streptococcus iniae challenge study was conducted after the 35‐day feeding trial, and the results showed that post‐challenge mortality of larvae fed the 11.5% lipid level was the lowest and enhanced the immune activities. |
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| Keywords: | fish larvae genetically improved farmed tilapia health lipid digestion molecular |
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