| This research adopts methods of eco-nutrition, physiology and molecular biology,to firstly study requirement characteristic, biological mechanisms, fleshy suitability ofdietary fat and protein nutrition on Atlantic salmon reared in recirculation aquaculturesystem (RAS) of China, it can provide a scientic basis for ecological nutritionregulation and fleshy improvement of ecological compound feed for Atlantic salmonin RAS.In order to investigate effects of dietary fat and protein on the growthperfomance，flesh quality, digestive enzymes and alkaline phosphatase activity, fatmetabolism enzyme, nonspecific immunity, water quality and mRNA relativeexpression of related growth gene of Atlantic salmon (Salmon salar L.), a random3×2two-factor animal experiment was conducted for56days in a recirculationaquaculture system (650.0±45.50g). The experimental diets include three fat levels(18%,21%,24%；F18,F21,F24) and two protein levels (38%,48%；P38,P48).Thenresults indicate that:(1) Studies have shown that fat nutritional requirements of farmed about600-900g Atlantic salmon in industrialized recirculation aquaculture systems（RAS）are reduced compared with the currently abroad net cage aquaculture, and dietary fat at about21%to24%can meet growth needs; Atlantic salmon has a higher demand forprotein nutrition, growth and feed utilization rate can significantly improve withdietary protein increased from38%to48%, weigh gain rate (WGR) significantlyimproving44.99%(P<0.01). This study result shows that combinations of mediumfat/high protein (F21P48) and high fat/high protein (F24P48) have excellent growtheffects, Weight gain rate (WGR) are significantly higher than low fat/low protein by125.86%and125.86%(P<0.01) respectively, feed conversion rate (FCR)significantly decreased by29.19%,30.00%respectively (P<0.01). Dietary lowprotein and high fat can reduce water ammonia nitrogen emissions of farmed Atlanticsalmon, optimizing cultivation environment.(2) It can produce the high quality of Atlantic salmon that are rich in EPA andDHA in indusrial recirculation aquaculture systems （RAS）of China. Both dietary fatand protein contents can affect contents of muscle fat and protein of Atlantic salmon,results show that medium fat level has a trend to increase muscle fat, dietary proteincan affect contents of muscle fat and protein, high protein level significantly increases5.83%muscle protein content compared with low level, and low protein improvesmuscle fat content. Content of muscle omega-3HUFA has positively related withdietary fat levels, and negatively correlated to protein, the content of muscle∑ω-3PUFA is significantly increased at high fat level than low by15.74%(P<0.05);Low protein can significantly improve muscle DHA, EPA content by11.91%,10.02%respectively (P<0.01); combinations of high-medium fat/low protein (P38F21,P38F24) are benificail to improve content of muscle unsaturated fatty acid. Mainlymuscle amino acid content is positively correlated with protein levels. Effects ofdietary fat and protein on the growth performance and meat quality showed thatbalance-moderation nutrient regulation is very important. This research proves thatthe combination of high fat/low protein is conducive to increase muscleomega-3HUFA and deposit main amino acid, promoting compound feed developmentin accordance with improving meat quality of industrial farmed Atlantic salmon.(3) This study proves that the medium fat level can significantly increased thestomach, intestinal, hepatic lipase activity of industrialization farmed Atlantic salmon, respectively higher11.52%(P>0.05),14.63%(P<0.05),4.31%(P>0.05) than low fatlevels. High protein level can promote increasing intestinal trypsin, liver trypsinactivity by8.23%(P>0.05),8.23%(P<0.05) respectively, and found that the activityof bowel and liver pancreas trypsin activity was much higher than pepsin activity.Preliminary showed that low fat and high protein can significantly improved intestinalAKP activity of Atlantic salmon (P<0.01), and significantly higher at low fat levelthan and medium high fat, by18.61%,31.70%(P<0.05) respectively, andsignificantly increased13.69%at high protein level than low (P<0.01), thusdeficiency of fat and protein nutrion can promote AKP activity to effectively absorbnutrients. This study reveals the relationship between dietary fat and protein levelsand intestinal nutrient absorption ability under industrial farmed Atlantic salmon,showing the importance of nutritional regulation of sea water fish farming, and itsmechanism of action remains to be further researched. Studies have shown thatmedium and high fat levels significantly improve serum SOD and MDA activity,respectively increased by10.32%(P<0.01) and reduced by4.49%(P>0.05) atmedium fat level than low; High protein level is beneficial to promote the activity ofserum LZM, C3, increased by9.49%(P>0.05),9.49%(P<0.05) respectively.(4) The study preliminarily shows that fat levels have significantly effects onactivity of Lipoprotein Lipase(LPL)，Hepatic Lipas（eHL）and total esterase (P<0.05),medium fat level is beneficial to improve LPL and HL activity, however，proteinlevels have no significant effects. Activity of HL, LPL and total esterase at mediumfat level are increased by21.57%,19.24%and21.57%at low respectively. Resultsindicate that protein levels have sensitive effect on content of fatty acid synthase (FAS)(P<0.01), low protein level can improve FAS content in muscle and liver, however，fat levels have no significant effects. Contents of muscle and liver FAS at low proteinlevel are higher than high, by12.90%and21.05%respectively. Hepatosomatic index(HSI) is increasing with increased dietary fat levels, and HSI at high fat level arehigher than medium and high by10.81%,3.36%respectively; Condition factor (CI) isfirstly increasing and then decresing with increased fat level, exiting a maximumvalue at medimum fat level, higher2.6%,4.17%respectively than high and low. P48F24has a maximum HSI, P38F21has a maximum CI.(5) Results preliminarily show that fat levels have significantly effect on IGF-I,but no significantly effect on GH. Medium fat level is more advantageous to increasethe relative expression of IGF-I gene mRNA in muscle and liver of Atlantic salmon,and higher than high and low by118.49%(P<0.01),118.49%(P<0.01),4.79%(P>0.05),137.42%(P<0.01); High protein level can promote mRNA abundance ofmuscle GH, IGF-I and liver IGF-I, and significantly increased by400.42%,226.46%and226.46%(P<0.01)respectively; The relative expression quantity of GHR genesmRNA is decreasing with increased dietary protein and fat levels. This study provesthat the combination of medium fat/high protein (P48F21) has an obvious promotingeffect on growth performance and GH/IGF axis relative genes expression of Atlanticsalmon, providing an important basis of molecular nutrition for ecological compoundfeed that is suitable flesh quality of industrialized farmed Atlantic salmon... |
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