Effect Of Dietary Non-phytate Phosphorus Levels On Performance,Caecal Microflora And Tibia Characteristics In Meat Ducks

This study was conducted to investigate the effects of dietary non-phytate phosphorus levels(NPP)on growth performance,nutrient utilization,intestine morphology,cecal microflora,tibia development and quality in meat ducks from 1 to 21 d of age.In total,525 one-d-old ducklings were fed with diets containing five levels of NPP(0.22,0.34,0.40,0.46 or 0.58%)for 21 days.Each dietary treatment consisted of 7 replicate cages of 15 birds.The results showed:1)Body weight gain(BWG,d 1-14,d 15-21 and d 1-21)and feed intake(FI,all period)increased(P<0.05)in a linear manner with increasing of dietary NPP levels.Ducks fed diets with 0.22%NPP had lower(P<0.05)BW(d 14 and d 21)than ducks fed other diets.The utilization of dry matter,calcium and phosphorus in 0.22%NPP were lower(P<0.05)than in 0.40%NPP.Ducks fed diet containing 0.46%NPP had the best performance,and FI also significantly higher(P<0.05)than diet containing 0.22%NPP.2)Serum alkaline phosphatase activity at 14 d and 21 d of age linearly and quadratically decreased(P<0.05)when increasing of dietary NPP levels,while serum phosphorus at 14d of age contents linearly and quadratically increased(P<0.05).3)Ducks fed diet containing 0.46%NPP had better intestinal morphology as compared to those fed the other four diets.With the increase of dietary NPP levels,duodenal muscle thickness at 14 d of age linearly increased(P<0.05),the activity of jejunal sodium-potassium-ATPase(d 14)and the mRNA expression of duodenal Na-Pi Ⅱ b(d 21)linearly decreased(P<0.05),and duodenal villi height(d 14)tend to increase linearly(P=0.077),while the activity of jejunal sodium-potassium-ATPase(d 21)(P=0.058)and the mRNA expression of duodenal Na-Pi Ⅱ b(d 14)(P=0.077)tend to decrease linearly.4)Cecal microflora in ducks at the phylum level of the top ten were the Firmicutes,Bacteroidetes,Actinobacteria,Tenericutes,Proteobacteria,Acidobacteria,Chloroflexi,Gemmatimonadetes,Fusobacteria,and Deferribacteres.Proportion of Firmicutes was dominant over 50%.There was a significant difference in the number(P=0.026)of Fusobacteria among treatment groups.The abundance of Fusobacteria linearly decreased(P=0.005)with the increase of dietary NPP levels,while the abundance of Subdoligranulum linearly increased(P<0.01)and ducks fed diets with 0.46%NPP had maximum OTUs number.5)Ducks fed diet containing 0.22%NPP lowered(P<0.05)the tibia quality,tibia strength,tibia length,diameter and density,and calcium content of tibia at 14 d of age,and tibia ash,calcium and phrosphrus content,and tibia diameter at 21d of age when compared with other diets.The relative expression of FGFR1(d 14)and the number of osteoclast(d 14)in tibia linearly decreased(P=0.043)with the increase of dietary NPP levels.6)The optimum requirement of NPP for BW,BWG and FI or tibia ash,calcium and phrosphrus content in meat duck aged at 14 d and 21 d or from 1 to 14 d,and from 1 to 21 d were 0.37%,0.35%or 0.37%,0.41%,0.37%,or 0.36%or 0.46%,0.47%or 0.39%,0.35%,0.40%or 0.40%based on broken-line regression,respectively,and were 0.47%,0.47%,or 0.47%,0.47%,0.48%,0.48%,or 0.47%,0.45%,or 0.46%,0.51%based on quadratic equation,respectively.These results suggested that dietary NPP levels could regulate F1,calcium and phrosphrus absorption of intestine,cecal microbial diversity,and the number of osteoclast in tibia of ducks.High dietary NPP level(0.58%)decrease the cecal microbial diversity;Low dietary NPP level(0.22%)increase the number of osteoclast and futher decrease the quality and development of tibia in meat ducks.