Effects Of Different Temperature On Dietary Protein Requirement,physiological Metabolism And Intestinal Microbial Community Of GIFT Tilapia(Oreochromis Niloticus)

1.A two-factor test(3 x 6)was carried out to evaluate the effects of water temperature,dietary protein,and their interaction on growth,body composition,and blood biochemistry of juvenile GIFT tilapia(Oreochromis niloticus)(The initial weight:38.75±0.61g).The fish were fed with six semi-purified diets contained graded levels(209.6,251.0,302.4,354.3,401.9 and 456.8 g/kg)of crude protein by triplicate to each water temperatures(22,28 and 34?)for 8 weeks.The results showed that the fish growth performance,feed utilization and protein conversion rate were significantly affected by dietary protein level and water temperature,the interaction of the two factors only significantly affected the weight gain rate,feed efficiency and protein efficiency.The crude lipid and crude protein content of whole fish were significantly affected by dietary protein levels,and the ash content changed significantly with the water temperature,while the interaction between them only had a significant effect on the crude lipid(P<0.05).The lowest lipid content in fish was recorded for the group fed with 456.8,354.3 and 401.9 g/kg protein diet at 22,28 and34?,respectively.The protein level and water temperature significantly affected serum biochemical indices measured in this study except for serum albumin(ALB)(P<0.05).Under the three water temperatures,fish fed the 354.3-456.8 g/kg protein diet had significantly lower content of TP,TG and TCHO than the fish which fed the other diets(P<0.05).Analysis based on broken-line regression of WGR and dietary protein,the optimal dietary protein requirement for GIFT tilapia(approx.40g)to achieve maximal growth performance are 374.4,301.7 and 304.9 g/kg under the three temperature conditions(22,28 and 34?),respectively.2.Water temperature is one of the most important environmental factors for fish.Fish could get the maximal growth and maintain a healthy physiological status at optimal temperatures.Whereas,when the water temperature exceeds the optimal range,the growth and physiology of fish such as temperature-sensitive tilapia will be affected.However,it hasn't been entirely revealed that the effect of water temperature on the metabolic mechanism of tilapia.Thus,A ~1H NMR-based metabolomics approach was used to explore the impact of water temperature on the liver and serum metabolic profile of tilapia.The fish(initial average body weight:38.75±0.61 g)were individually reared at three temperatures(22,28 and 34?)for 8 weeks.Nuclear magnetic resonance spectroscopy(~1H NMR)were used to determine significantly changed metabolites among all groups.The results showed that 47 metabolites in serum and 45 metabolites in liver were identified,respectively.In serum,changing metabolites were mainly involved in glycolysis,choline metabolism and lipid metabolism.Apart from glucose,glutamine and mannose,all those changing metabolites in the fish cultured at 34?were higher than that at 28?.And lactate,trans-4-hydroxyl,creatine,glucose,proline,leucine and valine were elevated in the fish cultured at 22?compared to the fish cultured at 28?.For liver tissue,changing metabolites were mainly involved in glycol metabolism and amino acid metabolism.All changing metabolites in the fish culture at 22?were higher than the fish cultured at 28?and 34?.Whereas in comparison to the fish cultured at 34?,maltose,glutamate,lysine,serine,glutamine,taurine and threonine were increased in fish cultured at 28?.In conclusion,the results indicated that low-water temperature has affected glycol metabolism and amino acid metabolism,reduced the utilization of amino acids and the derivatives in fish,which has led to reduce the growth rate and feed utilization of tilapia.And high-water temperature has significantly affected the choline metabolism and lipid metabolism of tilapia.It was probably an adaptive response to high water temperature.3.In order to study the effects of different culture temperatures on the intestinal microbes of tilapia,this study used 16S r RNA high-throughput sequencing technology to sequence the intestinal microbes of tilapia cultured at different temperatures,and analyzed the intestinal flora of tilapia.Changes in diversity as temperature changes.The tilapia gut samples(labeled LT,MT,HT)cultured at 22?,28?,and 34?were collected,and the total intestinal DNA was extracted.After amplification by PCR,Illumina Mi Seq was high.Flux sequencing,and then using bioinformatics methods to analyze the diversity of intestinal microbial composition of tilapia at different culture temperatures.Results:the effective sequences obtained from LT,MT and HT samples were all around 60,000,and the three groups of OUTs accounted for a large proportion,which could reflect the high similarity of the community.Analyze and compare the microbial populations of LT,MT and HT samples.There were no significant differences in the Ace index,Chao 1 index and Simpson index between the three groups(P>0.05),and the Shannon index of LT and MT was significantly different(P<0.05).Shannon index can reflect colony diversity.The results showed that diversity of intestinal colonies of tilapia showed great similarity at three temperatures,but the richness of tilipia intestinal flora changed significantly at 22?and 28?.There was no significant change in the intestinal flora at 34?,and the abundance of the microbial population of cultured tilapia was the highest at 28?.