| Phosphorus that is an essential mineral element distributed in various tissues of the annimals,and also is the most abundant mineral element in the digestive tract.The results showed that the development of digestive tract and its digestion and barrier function play an important role in meat ducks growp rapidly.And,it was not clear that appropriate level of non-phytate phosphorus in the diet of meat ducks.Thus,the purpose of this study was to investigate the effects of dietary non-phytate phosphorus（NPP）level on the performance,the development of digestive organ and its function,and intestinal barrier function in meat duck.With a single factor experiment design,a total of 768 1 days Cherry Valley male ducks were randomly allotted into 6 treatments,that contained 8 replicates per treatment,with 16 brids per replicate.The study designed six NPP levels,and the NPP level in basic diets corresponded to 0.24%,0.34%,0.44%,0.54%,0.64%and 0.74%,respectively.Four ducks per treatment that weight closed to average weight were selected for gavage test,and each duck was given Fluorescein isothiocyanate-conjugated dextran（FITC-d）at4.16mg/kg.The overall experimental period last 35 days.The results showed as follow:1)Ducks that fed the NPP level 0.24%and total phosphorus 0.45%suffered from severe symptoms of P deficiency after 5 d.The BW,BWG,ADG and FI of meat duck firstly increased and then decreased with the increase of NPP level.When NPP level was0.59%,the growth performance of meat ducks was the optimal.2)In 0.34%NPP group,the breast muscle percentage and the pH24h of thign muscle were remarkably lower than those of other treatment groups（P<0.05）.With the increase NPP level,the breast muscle shear force gradually increased,and in 0.64%and 0.74%NPP groups that was noticealy higher than that in 0.34%NPP group（P<0.05）.In 0.44%NPP group,the light of breast muscle and thign muscle were remarkably lower than 0.34%NPP group（P<0.05）.3)As the NPP level increased,several measured parameters,including the tibia fresh weight,length,strength,fat-free heavy of meat ducks at the 14 d and 35 d,firstly increased and then decreased,and reached the maximum in 0.54%NPP group.In 0.34%NPP group,the tibia ash of duck was significantly lower than that in other treatment groups（P<0.05）.4)The absolute weight of liver,pancreas,muscular stomach and glandular stomach firstly increased and then decreased with the increasing NPP level,and it reached the highest level in 0.54%NPP at 14 days.In 0.34%NPP group,the relative weight of liver was remarkably higher than those of other treatment groups（P<0.05）.In 0.64%NPP group,the absolute weight of pancreas and muscular stomach were largest,and noticeably higher than that in 0.34%and 0.74%NPP groups at 35 d.The relative weight of liver in 0.34%NPP group was significantly higher than those of other treatment groups at 35 d（P<0.05）.5)The jejunal and ileal absolute weight in 0.34%NPP group were significantly decreased at 14 d（P<0.05）.And the duodenal relative weight in 0.34%NPP group was noticeably higher than that in 0.44%NPP group at 35 d（P<0.05）.In 0.34%NPP group,the duodenal,jejunal and ileal relative length were significantly increaced than other treatment groups（P<0.05）.The duodenal,jejunal and ileal villus height in 0.44%NPP group were significantly increased than other treatment groups（P<0.05）,and also the duodenal and ileal villus-to-crypt depth were noticeably increaced（P<0.05）.The crypt depth of duodenum and jejunum in 0.64%NPP group were largest and remarkably higher than those of other treatment groups（P<0.05）.6)In 0.44%NPP group,the activity of amylase and trypsinase in pancreas were prominently higher than those of other treatments（P<0.05）.Lipase activity in 0.44%NPP group was significantly higher than that of 0.34%NPP group（P<0.05）,but the not noticeable difference was observed than other treatment groups（P>0.05）.The results showed that the highest activity that of duodenal maltase and jejunal sucras were observed in 0.54%NPP group,but not significant difference compared to other treatment groups（P>0.05）.In 0.44%NPP group,ileal maltase activity was the highest,which significant differed from that of 0.34%NPP group and 0.54%NPP group（P<0.05）.When compared with other treatment groups,the activity of alkaline phosphatase of duodenum and jejunum in 0.34%NPP group were prominently exceeded（P<0.05）.7)The apparent digestibility of the energy,DM,CP and EE gradually increased with the increasing NPP level,and the apparent digestibility of nutrients in 0.54%group were the best.In 0.34%NPP group,the apparent digestibility nutrients were prominently lower than those of other treatments（P<0.05）.8)The content of mucin 2（Muc2）and secretory immunoglobulin A（sIgA）were not prominently difference with increasing NPP level in jejunum of meat ducks at 35 d（P>0.05）,but had an increase tendency.When compared with other treatment groups,the content of FITC-d in the serum of meat ducks was remarkably exceed at 35 d（P<0.05）.9)Through quadratic regression analysis and built quadratic equation showed that when BW,BWG,ADG,FI,tibial fresh weight,strength,fat-free weight and ash reached the maximum value,the NPP level in diet for 1-14 days were 0.59%,0.59%,0.59%,0.59%,0.60%,0.53%,0.58%,0.64%,and the NPP level in diet for 1-35 days were 0.60%,0.60%,0.60%,0.58%,0.57%,0.57%,0.56%,0.59%,respectively.These results indicated that the diets of NPP were recommended 0.59%,0.58%at1-14 d and 1-35 d meat ducks,respectively.And,the diet NPP level can regulate digestive function and intestinal health with the enhanced function as follows:1.The appropriate of NPP level can promote the development of digestive organ such as liver,pancreas,muscular and glandular stomach and intestinal tract;2.The appropriate of NPP level can enhance the activity of digestive enzyme,and thereby improve the digestion and absorption ability of the energy,DM,CP,EE in nutrients;3.The appropriate of NPP level can improve the intestinal barrier function by reducing the intestinal permeability. |
