Effects of Calcium and Phosphorus Levels on Production Performance,Eggshell Quality and Bone Metabolism in New Yangzhou Layers

Six hundred New Yangzhou layers which were 36-week-old were randomly divided into four groups to get four kinds of treatments(high calcium and low phosphorus treatment,high calcium and high phosphorus treatment,low calcium and low phosphorus treatment,low calcium and high phosphorus treatment) by 2×2 factors.Each treatment had five repeats,feeding corn-soybean meal diet supplemented with different levels of calcium and phosphorus.The effects of different levels of calcium and phosphorus on the laying performance,eggs quality,endocrine and tibia quality were studied after 42 d feeding.In high calcium and high phosphorus treatment,the average laying rate was significantly higher than that in two low calcium treatments(P0.05).During experiment weight gain,eggs proportion,eggshell strength,eggshell thickness and eggshell proportion of the layers were significantly higher in high calcium and high phosphorus treatment than those in other treatments(P0.05).E2 level of the layers with high calcium and high phosphate treatment was significantly higher than those with low calcium and low phosphorus treatment(P0.05).However the differences in BGP,PTH,CT,tibia index and tibia density among treatments were not significant.The results indicated that production performance,egg quality and bone metabolism were desirable when calcium and phosphorus levels were 3.50%,0.32%,about 11∶1 in diet.