Effects Of Various Phosphorus Sources And Phosphorus Levels On Growth Performance In Juveniles Black Sea Bream, Acanthopagrus Schlegelii

Phosphorus is essential for fish and other aquatic animals. It's the components of bones and scales. Reproduction, disease resistance and enzyme activity are closely related with phosphorus. The phosphorus in feed is the main phosphorus source. Effect of various phosphorus sources on growth performance is quite different because of fish species, size and feed efficiency. On the other hand, Insufficient dietary phosphorus in feed will affect the normal growth and development, excessive dietary phosphorus will pollute water, so it's urgent to know the effects of phosphorus concentration and phosphorus sources in different period for different fish species.Total phosphorus concentration of the biggest weight gain and mineralization were 1.40% and 1.80%, when our lab studied the effects of dietary phosphorus on growth performance of juvenile black sea bream (Acanthopagrus schlegelii) (synonym:Sparus macrocephalus).This trial was conducted to research the effect of various phosphorus sources in different concentrations on growth performance, body composition, tissue phosphorus content, biochemical indices and phosphorus apparent digestibility in juvenile black sea bream. The healthy experimental fish of the same batch were randomly allotted to seven groups with triplicate of 20 fishes (average body weight,6.50±0.23g). There were six experimental diets (T1-T6) and one basic diet (T0). Basic diet contained 1.0% total phosphorus; T1-T6 groups were fed experimental diets with three phosphorus sources (mono-calcium phosphate, di-calcium phosphate, tri-calcium phosphate) in 1.40% and 1.80% total phosphorus. Add zeolite powder, make sure the dietary calcium level in all diets at the same level, and the ratio of Ca/P is 1.33:1. The faeces samples were collected in the last three weeks. After 8 weeks fed, fish were killed to collect the carcass, liver, muscle, vertebra, skin, scales and plasma samples, and then analyzed the collected samples for body composition, phosphorus content and biochemical indices.Phosphorus source had significant effect on the SGR, WGR, HSI, IPF, PER, efficiency of P utilization and phosphorus retention coefficient (P<0.05). The HIS and IPF were significantly increased in order MCP, DCP and TCP, but the rest were significantly decreased in that order (P<0.05). The IPF of control group (3.89%) was significantly higher than the experimental groups (P<0.05). The phosphorus sources have no significant effect on crude protein and ash in whole fish and muscle (P>0.05), but it significantly affected the fat in whole fish and muscle (P<0.05). And the fat was significantly increased in order MCP, DCP and TCP (P<0.05). Phosphorus source showed no significantly effect on ADC of protein, but ADC of dry matters phosphorus, lipid and phosphorus were significantly decrease in order MCP, DCP and TCP (P<0.05). The control group of ADC of lipid and phosphorus were significantly lower than the experimental groups(P<0.05),90.02% and 75.09%, respectively. The ash, calcium, phosphorus content and Ca/P ratio of spine, skin and scales showed an ascending trend were increase in order MCP, DCP and TCP. Interestingly, the calcium content was more sensitive for phosphorus concentration and phosphorus source instead of phosphorus content.The results show that the phosphorus concentration had no significant effect on the survival rate (SR), the specific growth rate (SGR), weight gain rate (WGR), hepotasomatic index (HSI), intraperitoneal fat ratio (IPF), protein efficiency ratio (PER), efficiency of P utilization and phosphorus retention coefficient (P>0.05). The SR of TP 1.80% group was significantly higher than the 1.80% group for the same phosphorus source (P<0.05), and that of control group (88.65%) was significantly lower than the other groups (P<0.05). Phosphorus concentrations had no significant effect on crude protein and ash in whole fish and muscle (P>0.05), but it significantly affected the fat in whole fish and muscle (P<0.05). And the fat was significantly decreased when phosphorus concentration increased (P<0.05). Phosphorus concentration showed no significantly effect on apparent digestibility coefficients (ADC) of dry matters, protein, phosphorus and lipid (P>0.05). The Ca/P ratio, the ash, calcium and phosphorus content of spine, skin and scales were increased when phosphorus concentration increased.The activity of lipase in liver, stomach, foregut and midgut was significantly affected by phosphorus source (P<0.05) and showed a downtrend in order MCP, DCP and TCP. The activity of AKP in serum, muscle and liver was significantly affected by phosphorus source (P<0.05) and showed ascending trend in order MCP, DCP and TCP. The variation tendency of CK activity was basically the same with the AKP. Phosphorus source had significantly effects on the content of TG, T-CHO and Glu. The Glu content was significantly decreased in order MCP, DCP and TCP, while the TG and T-CHO content was significantly increased (P<0.05).The activity of lipase in liver, stomach, foregut and midgut was significantly affected by phosphorus concentration (P<0.05) and showed an ascending trend with the increasing of phosphorus concentration. The lipase activity of T4 group was significantly higher than the others(P<0.05), it reached up to 44.31 U/gprot,318.52 U/gpro,96.15 U/gprot,94.28 U/gprot, respectively. The activity of AKP in serum, muscle and liver was significantly affected by phosphorus concentration and showed a downtrend with the increasing of phosphorus concentration (P<0.05).The variation tendency of CK activity was basically the same with the AKP. The CK activity of control group (31.36±1.05 U/mg prot) was significantly higher than the experimental groups, and that of T4 group (8.51±0.85U/mgprot) was the lowest. Phosphorus concentration had significantly effects on the content of TG, T-CHO and Glu (P<0.05). The Glu content was significantly increased with the increasing of phosphorus concentration, while the TG and T-CHO content was significantly decreased (P<0.05).In conclusion, from the point of phosphorus sources, the HIS, IPF, the lipid content of the whole fish and muscle, TG and T-CHO content were significantly increased in order MCP, DCP and TCP. The SGR, WGR, PER, ADC, efficiency of P utilization, phosphorus retention coefficientwere, the Ca/P ratio, the ash, calcium and phosphorus content of spine, skin and scales significantly and the Glu content in serum decreased in order MCP, DCP and TCP (P<0.05). For the phosphorus concentration, from the perspective of efficiency P utilization, the T1 (TP 1.40%, MCP) group was significantly higher than T4 (TP 1.80%, MCP) (P<0.05). But the T4 group was significantly higher than T1 from the perspective of the content of calcium, phosphorus and ash in tissue (P<0.05). There was no significantly different between T1 and T4 (P> 0.05).