Effect Of Dietary Non-phytate Phosphorus Levels On Growth Performance,Immune Function,and Caecum Microflora In Broilers From 1 To 21 Days Of Age

Two trials were conducted to investigate the effects of dietary non-phytate phosphorus level on growth performance,immune status,and caecum microflora in young broilers.Exp1:Effects of dietary non-phytate phosphorus level on growth performance,intestinal characteristics,immune status,and caecum microflora in broilersA total of 840 1-d-old commercial male Arbor Acres broilers were individually weighed and randomly aloted into 7 treatments（each treatment had 8 pens of 15 birds per pen）.Seven experimental diets were prepared by adding 0%,0.08%,0.14%,0.20%,0.26%,0.32%,0.42%of inorganic phosphorus（in the form Ca（HPO₄）₂·2H₂O）,into corn-soybean meal basal diet to containing 0.13%nonphytate phosphorus（nPP）.As a result,nPP levels of the experimental diets were 0.13%,0.21%,0.27%,0.33%,0.39%,0.45% and0.55%,respectively.The diets were fed to the broilers from 1-21 day.The results are showen as below:1)Broilers under the 0.13% nPP diet had 67.5%mortality rate from day 1 to 21.As the dietary nPP level increased,the day 21 body weight（BW）and day 1 to 21 BW gain（BWG）and feed intake（FI）of the broilers was quadraticly increased（P<0.01）.Broilers under0.33% nPP and 0.45% nPP had the optimal FI and BWG respectively.Using BWG and FI as markers,the suitable non-phytate phosphorus levels determined by establishing a quadratic regression model were 0.46% and 0.44%,respectively.2)Serum levels of Ca and P were also affect by dietary nPP levels（P<0.05）.Briyfly,Increases in dietary nPP levels linearly increased（P<0.05）serum P level.Highest levels of serum Ca and P were observed in broilers fed a 0.45% nPP.Dietary nPP levels had no effect on serum ALP activities（P>0.05）.3)The weights of duodenum,jejunum,and ileum were significantly increased by the increasing nPP levels（quadratic,P<0.05）in day 21 broilers.The relative weight of ileum was apparently increased by dietary nPP levels（P<0.05）.The activity of jejunal ALP was linearly decreased by the increasing dietary nPP levels（P<0.05）.The jejunal sodium-potassium ATPase（Na⁺-K⁺ATPase）was affected by dietary nPP levels in a dose-dependent manner（P<0.05）.Broilers fed 0.39% and 0.45% nPP diets have the lowest Na⁺-K⁺ATPase activity.when compared to the other treatments.4)Weights of the bursa of Fabricius and the spleen index of the broilers were quadraticly changed（P<0.05）with the increasing dietary nPP levels.Broilers under the 0.21% nPP diet had the highest spleen index and the lowest burasa when compared to the other treatments（P<0.05）.5)There were 362,16,42,9,3,and 25 unique caecum microbiota OTUs in broilers fed diets containing 0.21%,0.27%,0.33%,0.39%,0.45%,0.55% nPP,respectively,A total of 469 bacterial OTUS were shared by the broilers from all treatments.Broilers fed with a 0.21% nPP diet had increased numbers of unique OTUs when compared to the other treatment.The clustering analysis revealed that the greatest dissimilarity of the caecal microbial was identified between the broilers fed 0.21% and 0.39% nPP dites.PCA analysis showed that the samples from the 0.39% and 0.45%groups had relatively stable positions.Metastat analysis was performed at the Phyla level and found that the abundance of Bacteroidetes in the 0.21% nPP group was significantly lower than the that of 0.45% nPP group（P<0.05）.These results suggest that broilers fed low nPP diet（0.21% nPP）had decreased growth performance,suppressed bursa and spleen growth,and resulted the disorder of caecum microbiota diversity when compared to the other groups.The optimum nPP level was 0.39%.Exp 2:Effects of dietary non-phytate phosphorus level and LPS challenging on growth performance,tibia quality,immune status,and caecum microflora in broilersA total of 360 1-d-old commercial Arbor Acres male broilers were used in a 3×2 factorial design with 3 concentrations of dietary nPP（0.33%,0.39%,0.45%）and 2 stress condition（saline,LPS）.This experiment was carried out with six treatments,each treatment had 6 cages of ten birds.The broiler was intraperitoneally injected（1 mg/kg）with either LPS or saline at 14d,16d,18d and 20 of age.The results are shown as below:1)Dietary nPP levels had no effect on the day 14 BW,day 1 to14 BWG and FI of the broilers.Broilers fed 0.45% nPP had decreased F/G when compared to thoses fed 0.33% and 0.39% nPP diets.2)Broilers fed with 0.33% and 0.39% nPP diet had decreased（P<0.05）day 21 BW,day 15 to 21 BWG and day 15 to 21 FI when compared to those fed with the 0.45% nPP diet.Also,the LPS challenge decreased（P<0.05）the day 21 BW,day 15 to 21 BWG and day 15 to 21 FI in broilers.While no interaction was noted（P>0.05）,the LPS challenge induced a biger growth supperession,and caused more mortality in broilers fed 0.33% and0.39% nPP,when compared to broilers fed 0.45% nPP.3)Broilers fed with 0.33% and 0.39% nPP diet had decreased（P<0.05）serum Ca level and tibia Ca,P and ash content when compared to those fed with the 0.45% nPP diet.The LPS challenge increased（P<0.05）serum Ca level but decreased the volume of tibia in broilers.Interations were noted on serum Ca level,tibia volume and tibia ash content（P<0.05）.4)Either 0.39% nPP diet or the LPS challenge increased spleen weight（P<0.05）.5)When compared to the 0.33%diet,the 0.45% nPP diet increased the cecal Chao1and ACE indexes（P<0.05）in broilers.In case of LPS challenge,the broilers under 0.33% nPP diet had increased uumbers of cecum OTUs（216 vs 7）when compared to those under the 0.45% nPP diet.Also,abnormal caecum microbiota structure was observed in broilers under 0.33% nPP diet and with LPS challenge.The abundance of Bacteroidetes was increased and the abundance of Firmicute was decreased in broilers under 0.45% nPP when compared to those under 0.33% nPP.These results suggest that LPS challenge decreased the performance of broilers,and disrupted cecal microbial balance.Under the LPS challenge,the increased dietary nPP level（0.39%,0.45%）increased the growth of spleen,balanced the Ca and P metabolism,and improved the cecal microbial community structure,and subsequently,alleviated the LPS-induced negative impacts on growth performance.In conclusion,under normal conditions,the growth,intestional and immune organ growth,and the cecal microbial community of broilers could be well maintained by feeding diets contain 0.39% nPP.However,under the LPS challenge,the suitable nPP was 0.45% that was higher than that without the LPS challenge for maintaining the immune organ development,Ca and P balance,and cecal microbial balance.