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Utilization of phytate phosphorus and calcium as influenced by microbial phytase, cholecalciferol, and the calcium: total phosphorus ratio in broiler diets.

The present study was performed to evaluate the potential of microbial phytase and cholecalciferol (D3) for improving the utilization of phytate P and Ca and the influence of the Car:total (t) P ratio in a corn-soybean meal diet fed to broilers from hatch to 21 d of age. A 4 x 4 x 2 factorial arrangement of treatments was used: 1.1, 1.4, 1.7, and 2.0:1 Ca:tP ratio; 0, 300, 600, and 900 U of phytase/kg of diet; and 66 and 660 micrograms of D3/kg of diet. Another four treatments were included: the four Ca:tP ratios with 6,600 micrograms of D3 addition, but without phytase. Added phytase linearly increased (P < 0.001) BW gain, feed intake, toe ash content, and P and Ca retention; these measurements were negatively influenced by widening the dietary Ca:tP ratio, and synergetically improved by addition of D3. Increasing the Ca:tP ratio decreased (P < 0.001) all measurements in the presence or absence of supplemental phytase and D3. Dietary Ca:tP ratios between 1.1:1 to 1.4:1 appears critical to the efficient use of supplemental phytase and D3 for improving the utilization of phytate P and Ca. The addition of D3 in corn-soybean meal diets indicated a potential for improving the utilization of phytate P and Ca by increasing Ca and P retention by about 5 to 12% in birds, which led to an increase in toe ash content (P < 0.03). The enhanced phytate P utilization (P < 0.001) was also observed during assay of the phytase activity in the mixed diets with an addition of D3 and without added phytase. In summary, the findings of this study suggested that phytase, D3, and Ca:tP are important factors in degrading phytate and improving phytate P and Ca utilization in broilers.

6-Phytase↗

Influence of cage density and prior dietary phosphorus level on phosphorus requirement of commercial leghorns.

Two studies were conducted to determine whether cage density and prior dietary nonphytate P (NPP) level affect hens' P requirements. In Experiment 1, hens were housed at three cage densities (300, 400, and 600 cm2 or 46.5, 62.0, and 93.0 inches2/hen) and fed four levels of NPP (0.15, 0.25, 0.35, and 0.40%) for 6 wk to determine the effect of cage density on the P requirement. Egg production (EP), feed consumption (FC), egg weight (EW), and egg specific gravity (ESG) were measured to evaluate performance. Cage density influenced EP within Week 1 (P < 0.01), and during Weeks 5 and 6, there was a cage density x NPP-level interaction (P < 0.05). At 300 cm2, EP was more severely affected by 0.15 and 0.25% NPP than at 400 and 600 cm2. A linear decrease (P < 0.001) in FC was observed because of decreased NPP. Hens at 300 cm2 consumed 4 g less feed/hen per d than hens at 400 cm2. A linear decrease in EW was observed as the NPP level decreased (P < 0.01) from 0.25 to 0.15%, and there was no effect of cage density. Experiment 2 was conducted to determine the effect of prior dietary P levels on time required to create a P deficiency. Hens fed 0.4% NPP were divided into two groups and fed 0.25 and 0.4% NPP for 4 wk. At the end of 4 wk, hens fed 0.25% NPP were further divided into three groups and were fed diets containing 0.09, 0.25, and 0.30% NPP for an additional 6 wk. Hens fed 0.4% NPP were divided into three groups and fed diets containing 0.09, 0.4, and 0.45% NPP. Reduction of NPP from 0.4 and 0.25% to 0.09% reduced EP by 8.5 and 6.8%, respectively, within 3 wk. Prior NPP levels had no influence on time required to create a P deficiency in terms of EP. Reduction of NPP from 0.4 and 0.25% to 0.09% reduced (P < 0.05) FC. A decline in FC occurred 2 wk earlier in hens previously fed 0.4% than those fed 0.25% NPP. This result indicates that hens fed 0.4% NPP became P deficient more quickly than hens fed 0.25%. We concluded that cage density and prior NPP level affect the hen P requirements or time required to create a P deficiency.

Animal Husbandry↗

The use of low-protein, low-phosphorus, amino acid- and phytase-supplemented diets on laying hen performance and nitrogen and phosphorus excretion.

Two experiments were conducted to determine whether, by using a low-protein, amino acid-supplemented diet or a low-protein, amino acid-supplemented diet in conjunction with low-P, phytase-supplemented diet, the excretion of N and P could be reduced without affecting the productive performance of laying hens. Eight dietary treatments were assigned to Babcock B300 hens in each of 2 experiments that involved a positive control (16 to 16.5% CP) and a negative control (13% CP) with and without supplementation with the limiting essential amino acids. In experiment 1, supplementing the negative control with lysine, methionine, and tryptophan resulted in performance comparable to that obtained with the positive control, with the exception that egg weight was heavier for the negative control supplemented with amino acids. Supplementing the negative control with additional essential amino acids improved the performance higher than the positive control indicating that the positive control was deficient in one or more essential amino acids. In experiment 2, supplementing the negative control containing 0.2% nonphytate P (NPP) with all the limiting amino acids plus phytase resulted in performance comparable to the positive control group, which was fed 0.4% NPP without phytase. The results of a digestibility assay indicated that daily total P and N excretions of the negative control containing 0.2% NPP and supplemented with limiting amino acids and phytase were reduced by 48 and 45% of the positive control group, respectively, without compromising laying performance.

6-Phytase↗