| Phosphorus is an essential nutrient in animals and plays an important role in bone development and other biochemical metabolism.But excessive phosphorus in animal feed can also cause environmental pollution.Evaluation of the bioavailability of phosphorus in feed ingredients is the basis of precise nutrition of phosphorus and efficient utilization of phosphorus resources.In this thesis,the contents of available phosphorus and digestible phosphorus in some plant feed materials for broiler chickens were assessed and the effects of exogenous phytase on the bioavailability of phosphorus in different plant feed materials were studied by two experiments.The first experiment was conducted to determine the apparent availability and true availability of P in soybean meal(SBM),canola meal(CNM),cottonseeds meal(CSM),peanut meal(PM),corn distiller’s dried grains with solubles(corn DDGS),wheat bran(WB),wheat grain(WG)and wheat middling(WM).In the experiment,576 male Arbor Acres broiler chickens aged 23 days with similar body weight were assigned randomly into16 treatments with 6 replicate(cage)each and six birds in each cage.Sixteen diets were designed by combining 2 experimental factors which include 8 ingredient and microbial phytase(addition or not).Dietary P was only provided by the feed ingredient to be tested.A purified phosphorusfree(P-free)diet was prepared to determined endogenous P loss(EPL).Availability of P was evaluated by collecting feces trial.The results showed that the basal endogenous phosphorus loss(EPL)was 97.45mg/DMI.The true availability of P in soybean meal,canola meal,cottonseeds meal and corn DDGS was53.90%,53.22%,54.73% and 49.45% respectively,which was much higher than peanut meal(42.76%),wheat bran(38.26%),wheat grain(36.77%)and wheat middling(38.33%).Addition of phytase increased the apparent or true availability of P significantly(P<0.05).Phytase had the greatest improvement for wheat ingredients(wheat grain 40.18%;wheat middling 35.61%;wheat bran 27.47%)and soybean meal(31.52%),followed by canola meal(23.07%),cottonseed meal(14.43%),peanut meal(11.51%)and Corn DDGS(6.69%).The available phosphorus equivalent of 1000 FTU microbial phytase corresponding to different ingredients was between 0.2g(corn DDGS)and 1.2g(canola meal).The second experiment was conducted to determine the apparent and standardized ileal digestibility(AID and SID)of phosphorus(P)in soybean meal(SBM),canola meal(CNM),cottonseeds meal(CSM),peanut meal(PM),corn distiller’s dried grains with solubles(corn DDGS),wheat bran(WB),wheat grain(WG)and wheat middling(WM).In the experiment,576 male Arbor Acres broiler chickens aged 23 days with similar body weight were assigned randomly into16 treatments with 6 replicate(cage)each and six birds in each cage.Sixteen diets were designed by combining 2 experimental factors which include 8ingredient and microbial phytase(addition or not).Dietary P was only provided by the feed ingredient to be tested.A purified phosphorus-free(P-free)diet was prepared to determined endogenous P loss(EPL).Digestivity of P was evaluated by collecting ileal digesta trial.The results indicated that significantly higher standardized ileal digestibility was recorded in SBM(52.01%),corn DDGS(49.41%),CNM(47.02%),and CSM(46.09%)compared to WB(38.46%),PM(37.98%),WG(36.90%),and WM(35.69%).Addition of microbial phytase improved the SID of P by more than 40% in SBM and WM.The others were improved from 31.55% in canola meal to 37.77% in cottonseed meal and the least improvement was recorded in corn DGGS(5.12%).The determined ileal endogenous phosphorus loss(EPL)of this study was 46.28mg/kg DMI.The feedstuffs ileal digestible P equivalent value of 1000FTU/kg phytase was ranged from 0.2g to 1.6g.In summary,the true utilization rate of phosphorus in the plant feed evaluated was between 36.77%(wheat)and 54.73%(cottonseeds meal),and the standardized ileal digestibility of phosphorus was between 35.69%(wheat middling)and 52.01%(soybean meal).In the whole digestive tract and ileum level test,the improvement effect of 1000 FTU phytase on the bioavailability of phosphorus was significantly different with the different feedstuffs.In general,the true availability of phosphorus in the t’ested feed stuffs increased by 10.23%-41.35%,and the standardized ileal digestibility increased by5.12%-52.43%.The results of this study enrich the key data of feedstuffs and provide experimental basis for accurately evaluating the phosphorus equivalent of phytase. |
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