| This research,grass carp(Ctenopharyngodon idella)as the research object and soybean oil as fat supplement source,calcium dihydrogen phosphate as the phosphorus source,was conducted to study the optimum supplementation of calcium dihydrogen phosphate at the two different lipid levels,the effects of the combined action between phosphorus and lipid on growth and metabolism of grass carp and compare the effects of bile acid and sucrose fatty acid ester In high lipid diet.The experiments was divided into three parts as follows:Experiment one: To investigate the effect of different calcium dihydrogen phosphate added into low lipid(4.0%)diet of grass carp larval growth,body composition and biochemical indexes,Five levels of calcium dihydrogen phosphate(0%?1.0%?2.0%?3.0% and 4.0%,respectively)were added into low lipid(4.0%)diet for grass carp.The feeding trial(initial weight 105.23±0.55g)were randomly divided into 5 groups with 3 replicates in each group and 15 fish per replicate.Every ration group were raising in the 1.2m×0.5m×0.35 m glass aquarium and the feeding rate was 3.0%-5.0%.The experimental period lasted for 56 days.The result showed that: There were significant effects on weight gain rate(WGR),feed coefficient rate(FCR),body mass ratio(VSI).The contents of total phosphorus and crude ash of whole fish were significantly increased and stable,while the water content of whole fish was not significantly different,and the lipid content of whole fish,muscle and liver were significantly decreased.Intestinal amylase(AMY),intestinal lipase(LPS),intestinal trypsin(TPS)activity were significantly increased.The total antioxidant capacity(T-AOC)activity of the liver was significantly increased.the content of malondialdehyde(MDA)in the liver was opposite and reached the lowest at 3.0% level.Cholesterol(TC)and triglyceride(TG)were decreased,and the activities of serum alanine aminotransferase(GPT)were significantly decreased,while the serum AKP activity increased significantly and reached the maximum at 3.0% level.Carnitine palmitoyl transterase-1(CPT-1)activity increased,and the activity of acetyl-CoA carboxylase(ACC)decreased first and then increased.Conclusions As a result,Taking the growth performance as the index,the optimal level of calcium dihydrogen phosphate in grass carp(100 ~ 250 g)is 2.96% ~3.15%.Experiment two :The study was conducted to evaluate the effect of different calcium dihydrogen phosphate level added into high lipid(8.0%)diet of grass carp larval growth,body composition and biochemical indexes.Five levels of calcium dihydrogen phosphate(0%?1.0%?2.0%?3.0% and 4.0%,respectively)were added into high lipid(8.0%)diet for grass carp.The results showed that the WGR of the grass carp increased first and then decreased with the increase of the level of MCP in the high lipid diet,while the FCR showed the opposite trend,and the dirty body ratio of the grass carp decreased.The crude lipid of the whole fish,the muscle crude lipid and the liver crude lipid content showed the ascending trend first,and the crude protein and the crude lipid of the whole fish showed the opposite trend.The content of phosphorus in the whole fish increased first and then stabilized.Serum TC and TG decreased first and then increased,and serum AKP increased first and then decreased.The LPS and AMY of the grass carp increased first and then decreased,while the TPS increased first and then decreased.Serum T-AOC showed an upward trend,then the liver MDA was the first decline after the upward trend.The liver CPT-1 activity showed a trend of ascending,while liver ACC activity decreased first and then increased.Quadratic brken-line model analysis on weighe gain and feed conversion rate,The optimum content of calcium dihydrogen phosphate was 2.96%~3.26%.Experiment three: The study was conducted to investigate the emulsifying effect of emulsifier supplemented with high lipid diet and Compare of bile acid and sucrose fatty acid ester larval growth,body composition and the influence of the biochemical indicators of grass carp.The bile acid groups were fed with dietary supplementation of bile acid 500 mg / kg diets in the basal diet.The sucrose fatty acid ester group was fed with 500 mg / kg of sucrose fatty acid ester in the basal diet,Each diet was fed to triplicate groups of 15 grass carp with an initial weight of(105.23 ± 0.55)g for 56 d.The contents of serum T-AOC,TC and TG were decreased.the FCR and visceral crude lipid were significantly increased,and the activities of lipase and serum AKP were significantly increased.The effects of bile acid and sucrose fatty acid ester on the growth performance of grass carp and the content of MDA in grass carp were not significantly different.Compared with the two emulsifiers,Sucrose fatty acid ester can significantly increase the protein precipitation and reduce the accumulation of visceral lipid,while the bile acid group can improve the intestinal lipid and protein digestibility,promote the body's antioxidant capacity than sucrose fatty acid ester group.In summary,the following conclusions:1.With the growth performance as the index,the best addition of calcium dihydrogen phosphate was 2.96% to 3.15% for grass carp in low lipid diet(4.0%).The optimum additions of calcium dihydrogen phosphate in high lipid diet(7.0%)was 2.96% ~ 3.26%.2.Bile acid and sucrose fatty acid ester can significantly improve the growth performance and feed efficiency,but there is no significant difference between the two emulsifiers.3.In the same level of calcium dihydrogen phosphate added,high lipid group lower lipid group did not show a significant growth advantage.the growth performance difference of high lipid and low lipid group diet is not obvious is one of the reasons for the lack of emulsifier in high lipid feed. |
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