| Takifugu obscurus is famous for important and rare fish in Yangtze River as its excellent genetic potential and high nutritional value, which has a wide range of market prospect. However, the research about the nutritional requirements and compound feeds of takifugu obscurus in facility farming was almost blank. This study explored the effects of combinations with protein, lipid and protein sources on growth, water quality and physiological metabolism in takifugu for the first time, aimed to provide valuable theory basises and pactical references for nutritional manipulation and special ecological feed development of takifugu obscurus in facility farming.With applied originally new concepts of combination effects, trophic structure and system regulation from modern nutrition, directed by the theories and methods of eco-nutriology of aquatic animals, physiology and biochemistry, this study designed a 3×2×2 three-factor experiment, which included two main nutritional elements( 3 protein levels with 43%, 40% and 37%, designated as P43, P40 and P37, and 2 lipid levels with 10% and 7%, designated as L10 and L7), and one protein source( 2 fish meal levels with high fish meal(49%-55%) and low fish meal(39%-45%), designated as FH and FL), formulated twelve treatment groups(1#-12#) in triplicate for 77 days. The study was conducted to explore the influences and effects on growth, digestion and absorption enzymes, serum immunity, antioxidant capacity and transaminase metabolism in takifugu obscurus(initial weight: 172.87±6.71g) and water quality. The results were followed:1. The results of growth showed, treatments 1#(P43L10FH) and 9#(P40L10FL) improved significantly, the WGR increased by 35.11%-79.98% and 26.67%-54.32% respectively, the FCR reduced by 58.11%-76.35% and 47.17%-64. 15% respectively. Also, treatments 3#(P40L10FH), 11#(P37L10FL) and 7#(P43L10FL) could enhance growth performance significantly or obviously. Different treatments had no significant effects on survival rate, body feature and viscera. High lipid significantly increased the CF. The new discovery was that 9#, 11# and 7# in FL treatments improved the growth of trial fishes significantly or obviously due to prominent positive effect of nutritional elements and sources combinations and facilitation of high lipid, which not only saved the fish meal sources, but also cut down the feed costs, providing the valuable references in theory and practice.2. Water environment results showed, the concentrations of A-nitrogen, Nnitrogen and phosphate of FH treatments and FL treatments containing high protein were higher than those of other FL treatments, which of treatments 11#, 9#, 7# and 1# were lower relatively. A-nitrogen concentration of treatments 11# and 9# reduced by 42.97% and 37.5% compared to that of treatment 2# respectively, while N-nitrogen concentration significantly reduced by 43.59%-48.84% and 51.28%-55.81% respectively; Phosphate concentration of treatments 9#, 1# and 11# decreased by 26.85%, 28.70% and 30.56% significantly compared to that of treatment 2#. High lipid tended to decline both phosphorus concentration and COD. In prospect of eco-nutrition, 9# and 11# in FL treatments could both reduce water pollution and improve growth, which were advisable.3. Digestion and absorption results showed, the activities of trypsin and intestinal lipase of the FL treatments(9#, 11# and 7#) significantly enhanced, trypsin activity of treatment 9# significantly increased by 21.09% compared to that of treatment 1#. Intestinal lipase activity of treatments 9#, 11# and 7# improved by 22.32%, 15.68% and 14.61% respectively compared to that of treatment 3#, but had no significant differences with treatment 1#. However, activities of AKP and Na+-K+-ATPase had no significant differences in different treatments, which of treatments 9# and 1# enhanced obviously and that of treatments 11# and 7# were higher relatively. Meanwhile, high lipid could significantly increase the activities of absorption enzymes, and showed the trend of enhancing most digestion enzymes activities. Activities of intestinal lipase and Na+-K+-ATPase of L10 could markedly improve by 21.06% and 12.14% compared to those of L7. The digestion and absorption results in treatments 9# and 11# were in line with the growth performance and water environment results, which were considered as the mechanism of digestive physiology.4. Immunity and anti-oxidation capacities results showed, different treatments showed no significant differences in immunity(P>0.05), though, the contents of serum total protein, globulin, and the activity of LZM in treatments 1#, 3#, 7# and 9# increased obviously. Activity of SOD in liver of treatments 1# and 2# were highest, which of treatments 9# and 11# were higher significantly or obviously than that of other FL treatments, and which of treatment 9# improved by 10.89% than that of treatment 8#. The contents of MDA in liver of treatments 2#, 1#, 9# and 11# were lowest successively, and reduced by 46.95%, 41.46%, 34.15% and 23.78% respectively compared to the highest of treatment 6#. Meanwhile, high lipid could more improve the antioxidant capacity than high protein. The above results demonstrated that trial fishes of treatments 9#, 11# and 7# showed higher oxidation and immunity resistance, indicating the body healthy condition improved, leading to improve growth indirectly. That might be the mechanism of nutrition-immune.5. Transaminase results showed, different treatments had no significant differences in GPT activity in liver(P>0.05), though, which of treatments 1#, 2#, 3#, 7# and 9# were higher obviously. The activity of GOT in liver of FH treatments(1#-6#) improved significantly or obviously than that of FL treatments(7#-12#), which of treatment 1# significantly increased by 28.2%-37.31% compared to that of FL treatments, which of treatments 7# and 9# were obviously higher than other FL treatments. Activities of GOT and GPT in serum of FH treatments(1#-6#) decreased extreme significantly than those of FL treatments(7#-12#), which of treatment 1# significantly or obviously decreased by 26.61%-62.3% and 49.74%-76.9% respectively compared to those of FL treatments, and which of treatment 9# reduced obviously. Meanwhile, high protein could more improve the activity of GOT in liver than high lipid in FL treatments, revealing that if the fish meal instead of animal and plant proteins is in higher substitute proportion, improving protein level in diet would enhance transaminase activities, leading to promote protein metabolism. The mechanism of which needed to be further investigated.In conclusion, the experimental results initially showed, the changing levels, combinations and interactions of nutrimental elements and sources combinations had significant or extremely significant effects on growth, water environment, digestion and absorption, immunity and antioxidant, and transaminase metabolism of takifugu obscurus in facility farming. The preliminary optimum combinations were 1#(P43L10FH), 3#(P40L10FH), 9#(P40L10FL) and 11#(P37L10FL), which could be taken into account of the growth, digestive physiology, immunity and antioxidation. Furthermore, treatments 1# and 9# were excellent combinations which also could improve water environment obviously.The most valuable discovery was that 9# and 11# in FL treatments presented a double effect feature of improving growth and water environment significantly or obviously, which would provide valuable theory basises and practical references for the nutritional regulation and special ecological feed development in takifugu obscurus because of saving fish meal resources and decreasing feed costs. The experiment found out basically that high lipid presented an outstanding positive effect in the FL treatments. Studies of physiology mechanism indicated that high lipid tended to enhance activities of most digestion and absorption enzymes, and antioxidant capacity; If the plant and animal protein sources were in high ratio of substitute for fish meal, improving protein level in diet could enhance transaminase activities to promote protein metabolism. |
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