Studies On Dietary Phosphorus Requirement Of Young Siberian Sturgeon (Acipenser Baeri)

Phosphorus is a necessary constant mineral element for fish growth,which is one of the main components in bones,teeth and scales,at the same time,it has an important physiological function in maintenance of fish acid-base balance,regulation of osmotic pressure,constitutes a coenzyme and organic phosphorus compounds.Also,it plays important role in promoting blood coagulation, muscle contraction,transmission of nerve function and maintaining the integrity of cells. Phosphorus level in dietary neither too high nor too low is conducive to fish grow,a thorough study in the phosphorus requirement for fish has an important theoretical guidance and application meaning to develop feed,while plays a positive role in eutrophication control and maintenance of ecological balance.In order to determine the requirement phosphorus for Siberian sturgeon,the influences on growth performance,whole fish body,muscle,bone plates,vertebrae and plasma biochemical parameters of Siberian sturgeon by different levels of phosphorus was studied.495 healthy fishes weighed average14.50g were selected from stock and randomly distributed(15each) into 33 tanks (eleven treatment with three replicates each),and monobasic sodium phosphate in diets served as the phosphorus source,analyzed concentration P ranged from 0.12%to 1.38%in dry matter.The results showed that:1.The growth performance of Siberian sturgeon improved significantly with the level of phosphorus levels increasing,weight gain rate and specific growth rate arrived at 431.94%and 2.98%/d for the maximum respectively while the phosphorus level up to 0.60%,however,when the phosphorus levels reach 1.19%,the weight gain rate decreased;hepatosomatie index and viscerosomatic index showed the opposite trend to weight gain rate.Dietary phosphorus had no significant effect on condition factor(P＞0.05).2.With the levels of phosphorus in dietary increasing the crude fat content decreased,there was no significant effect on the crude protein,moisture(P＞0.05),fat content had no significant difference when the phosphorus levels greater 0.29%,body ash and phosphorus content remained stable while dietary phosphorus more than 0.99%(P＞0.05).3.Supplementation of dietary phosphorus had no significant effect on the muscle moisture, crude protein,crude fat and phosphorus content(P＞0.05),but when phosphorus levels range from 0.18%to 1.19%,crude ash of muscles increased with the phosphorus levels gradually increasing, then remained stable.4.There were positive correlations between ash,calcium and phosphorus content in bone plates and dietary phosphorus levels.With the levels of phosphorus in dietary increasing these parameters in vertebrae increased,and reached maximum at level of the 0.69%,as well,there was no significant effect on calcium/phosphorus ratio in bone plates and vertebrae.5.Dietary phosphorus had significant effect on plasma calcium,plasma phosphorus content and alkaline phosphatase activity(P＜0.05).With the levels of phosphorus in dietary increaseing from 0.12%to 0.29%,plasma calcium,phosphorus content were significantly increased(P＜0.05) and remain stable between 0.29%and 0.60%.Plasma alkaline phosphatase activity increased with phosphorus levels gradually rising and reached maximum at level of 0.69%(232.71 IU / L),at the same time,plasma calcium,plasma phosphorus content reached maximum,then these indexes showed a gradual downward trend,when the phosphorus levels were greater than 0.99%they maintain a stable status.6.The changes of plasma total protein content,albumin protein content,globulin protein content were gradually rising with the levels of phosphorus in dietary increasing and at 0.69% reached the highest(232.71 IU / L),then with the phosphorus levels decreased gradually,when phosphorus level was higher than 0.29%plasma cholesterol and triglyceride content had no significant differences(P＜0.05).We concluded that when the water temperature was 19.50±0.50℃,the requirement of dietary phosphorus for young Siberian sturgeon of an initial mean weigh of 14.50±1.00g,1.Based on WGR of young Siberian sturgeon as the evaluating index,we can conclude that the requirement of dietary phosphorus for young Siberian sturgeon was 0.50%or 5.00g per kilogram dry diet.2.Based on phosphorus content in body of young Siberian sturgeon as the evaluating index, the requirement of dietary phosphorus for young Siberian Sturgeon was 0.87%or 8.70g per kilogram dry diet.3.Based on phosphorus content in vertebra of young Siberian sturgeon as the evaluating index,the requirement of dietary phosphorus for young Siberian sturgeon was 0.44%or 4.40g per kilogram dry diet.4.Based on phosphorus content in bony plate of young Siberian sturgeon as the evaluating index,the requirement of dietary phosphorus for young Siberian sturgeon was 1.04%or 10.40g per kilogram dry diet.