DIETARY PHOSPHORUS REQUIREMENT OF YOUNG ABALONE, HALIOTIS DISCUS HANNAI INO.

An experiment was performed to determine the dietary phosphorus requirement of the young abalone, Haliotis discus hannai. Five semi-purified diets were formulated to provide a series of graded levels of dietary total phosphorus (0.23%-1.98) from monobasic potassium phosphate (KH2PO4). The brown alga, Laminaria japonica, was used as a control diet. Similar size abalone were distributed in a single-pass, flow-through system using a completely randomized design with six treatments and three replicates each treatment. The abalone were hand-fed to satiation with appropriate diets in excess, once daily at 17:00. The feeding trial was run for 120-d. Survival rate and soft-body to shell ratio (SB/S) were constantly maintained regardless of dietary treatment. However, the weight gain rate (WGR), daily increment in shell length (DISL), muscle RNA to DNA ratio (RNA/DNA), carcass levels of lipid and protein, soft-body alkaline phosphatase (SBAKP), and phosphorus concentrations of whole body (WB) and soft body (SB) were significantly (ANOVA, P<0.05) affected by the dietary phosphorus level. The dietary phosphorus requirements of the abalone were evaluated from the WGR, DISL, and RNA/DNA ratio respectively, by using second-order polynomial regression analysis. Based on these criteria, about 1.0%-1.2% total dietary phosphorus, i.e. 0.9%-1.1% dietary available phosphorus is recommended for the maximum growth of the abalone.

Effect of dietary phosphorus content on milk production and phosphorus excretion in dairy cows

Background：Phosphorus（P） supplementation is costly and can result in excess P excretion.This study investigated the effects of reducing dietary P on milk production and P excretion in dairy cows over a full lactation.Method：Forty-five multiparous Holstein dairy cows were divided into 15 blocks according to expected calving date and previous milk yield,and assigned randomly to one of the three dietary treatments：0.37,0.47,and 0.57%P（DM basis）;these P levels represent the NRC recommendations,Chinese recommendations,and the amount of dietary P commonly fed by Chinese dairy farmers,respectively.Average daily feed intake was calculated from monthly data on feed offered and refused.Milk yields of individual cows were recorded weekly,and milk samples were taken for analysis of protein,fat,solids-not-fat,lactose,and somatic cell count.Blood samples were collected on days-6,-3,0,3,6 relative to calving,and then monthly throughout lactation,and analyzed for P and Ca concentrations.Spot samples of feces and urine were collected for 3 consecutive d during weeks 12,24,and 36,and P concentrations were analyzed.Reproduction and health data were recorded.Results：Dietary P did not affect dry matter intake or milk yield（P〉 0.10）.Milk fat content was slightly higher in cows fed 0.37%P than in cows fed 0.47%P（P = 0.05）.Serum concentrations of P and Ca did not reflect dietary P content（P〉 0.10）.Fecal and urinary P both declined linearly（P〈 0.05） as dietary P decreased from 0.57 to0.37%.Fecal P content was 25%less when dietary P was 0.37%compared to 0.57%.Health events and reproductive performance were not associated with dietary P content（P〉 0.05）.Conclusions：Lowering dietary P from 0.57 to 0.37%did not negatively affect milk production,but did significantly reduce P excretion into environment.

Effects of dietary phosphorus level on growth,body composition,liver histology and lipid metabolism of spotted seabass(Lateolabrax maculatus)reared in freshwater

The present study was conducted to determine the effects of dietary phosphorus(P)levels on growth performance,body composition,liver histology and enzymatic activity,and expression of lipid metabolism-related genes in spotted seabass(Lateolabrax maculatus).Seven diets were prepared to contain available P levels of 0.48%(the control group),0.69%,0.89%,1.10%,1.28%,1.51%and 1.77%and feed fish(4.26±0.03 g)to satiety twice daily for 10 weeks.Significantly higher weight gain and specific growth rate were recorded at P levels of 0.69%-1.51%compared to the control group.Feed conversion ratio decreased with increasing P levels up to 0.89%and increased thereafter.The lowest liver lipid content,viscerosomatic index and lipid content of whole-body were obtained in the 0.89%-P group among dietary treatments.P and calcium(Ca)contents in whole body were increased,while liver triglyceride and cholesterol contents were decreased with increasing dietary P levels from 0.48%to 1.77%.The highest activity of hepatic lipase was recorded in the 1.10%-P group among dietary treatments.Compared to the control group,1.10%P enhanced the proportion of HUFA and reduced the proportion of SFA and MUFA.The histological observations showed that P deficiency(0.48%)led to the vacuolization of hepatocytes and increased number of lipid droplets.Meanwhile,overall liver tissue structure was improved when P level increased to 1.28%.Compared to the control group,expression of lipid metabolism-related genes such as FAS,ACC-2 and SREBP-1 was decreased at 0.89%-1.10%P group while an opposite trend was observed in the expression of PPARa2 and CPT-1 genes.The current study showed that 0.89%dietary P levels could promote growth performance of spotted seabass and reduce lipid accumulation in the liver.A broken-line regression analysis based on weight gain showed that the optimum dietary P level(available P)for juvenile spotted seabass reared in freshwater was 0.72%.