Effect Of Phosphorus Source And Level On Performance, Egg Quality, And Bone Quality Of Laying Hens

The experiment was conducted to investigate the effects of different phosphorus levels from mono-dicalcium phosphate (MDCP) or dicalcium phosphate (DCP) on the performance of laying-hens and the eggshell quality. A total of 1 170 commercial Lohmann pink-shell laying hens of 25-wk-old were randomly assigned to 1 of 13 diets involving 1 control plus 2×6 factorial completely randomized arrangement. The 2 phosphorus sources were MDCP and DCP; 6 phosphorus supplementation levels were 0.0.05%,0.10%,0.15%,0.20%,0.25%, and 0.30%. The corn-soybean meal basal diet contained 0.12% non-phytate phosphate (NPP) and all diets were powdery. Feed and water ad libitum.Each treatment consisted of 6 replicates of 15 hens each. The experiment lasted 24 wk. The result showed:1. PerformanceNo significant difference was observed on performance by phosphorus source and source by level interaction (P>0.05). At the experiment 21-24 wks, MDCP can increase the ADFI significantly (P<0.05). Hens fed the basal diet had lowest egg production, egg mass, egg weight, ADFI, with the highest mortality and feed to egg ratio (P<0.05). Added 0.05%-0.30% NPP can significantly increase laying performance, egg mass, and ADFI, while feed to egg ratio was decreased significantly (P<0.05).There was no significant difference in laying performance, egg mass, ADFI, and feed to egg ratio when fed the diets with NPP supplemented level from 0.10% to 0.30% (P>0.05). Egg weight and ADFI increased firstly then decreased when NPP increasing. Increasing NPP level decreased mortality, there was on death at 0.20% and 0.25%supplemented NPP level, but it turn up at 0.30% supplemented NPP level.2. Egg qualityThere was no significant difference on egg shell quality by phosphorus source and sources by levels interaction (P>0.05), MDCP increased dirty egg percentage at 9～12 wks (P<0.05). Dietary NPP level had no significant effect on eggshell thickness and eggshell to egg ratio (P>0.05). Hens fed the basal diet had the highest dirty, cracked and broken, soft, and malformation egg percentage, with the lowest eggshell strength (P<0.05). There was no significant effect on cracked and broken, soft, malformation egg percentage, and eggshell strength when hens fed the diets with NPP supplemented level from 0.05% to 0.30%, while no significant difference in dirty egg percentage when NPP supplemented level between 0.10% and 0.30% (P>0.05).3. Bone qualityThere was no significant effect on bone strength, content of calcium, phosphorus and ash of tibia, concentration of calcium, phosphorus, AKP, PTH, CT, and 1,25(OH)2D3 of serum, as well as expression level of CaBP-D28k and NaPi II b in the intestinal and uterus (P>0.05). Dietary NPP level had no significant effect on AKP activity (P>0.05). Hens fed the basal diet had the lowest BBS, calcium, phosphorus, and ash of tibia, calcium and phosphorus in serum, with the highest content of PTH, CT, and 1,25(OH)2D3 in serum (P<0.05). There was no significant effect on calcium content of tibia, calcium, phosphorus, PTH, CT, and 1,25(OH)2D3 content of serum when hens fed the diet with supplemented NPP level between 0.05% and 0.30% (P>0.05) (except hens fed the diet with 0.05% supplemented NPP level had higher PTH and 1,25(OH)2D3 content of serum than 0.30%), while no significant difference in BBS and ash content of tibia when supplemented NPP level from 0.10% to 0.30% (P>0.05). Nonphytate P level had a linear effect on ash content of tibia, y= 10.986x+ 56.331 (R2=0.9272).Dietary NPP level had significant effect on expression level of CaBP-D28k in duodenum, but not in jejunum, ileum, or uterus. Hens fed the diet with 0.30% supplemented NPP level had lower expression level of CaBP-D28k in duodenum than 0.10% (P<0.05). Dietary NPP level had different effect on expression level of NaPi II b in duodenum and jejunum, but not in ileum. Hens fed the basal diet had lower expression level of NaPiⅡb in duodenum and jejunum than 0.10% and 0.20% supplemented NPP level (P<0.05). The interaction of phosphorus source by level had significant effect on expression level of NaPi II b in duodenum (P<0.05).In conclusion, MDCP can completely replace DCP in the diet of laying hens. The basal diet with 0.12% NPP could not meet the requirement of 25-to 49-wk-old laying hens. Performance, egg quality, and bone quality were improved when hens fed the diet with supplemented NPP level from 0.05% to 0.30%. The suitable supplemented NPP level in corn-soybean meal diet with NPP 0.12% for 25-49 wks hens was 0.10%.