Response of broiler chickens to different levels of calcium,non-phytate phosphorus and phytase

1. Five hundred and seventy six-d old Ross 308 broiler chicks (6 cages per diet, 8 birds per cage in 3 × 2 × 2 factorial arrangement) were fed on maize–soybean meal-based diets containing three concentrations of Ca (6, 8 or 10 g/kg), two concentrations of non-phytate phosphorus (NPP) (3 or 4 g/kg) and two levels of exogenous microbial phytase (0 or 500 FTU/kg) from d 0 to 35.

2. Body weight (BW), feed intake (FI) and mortality records were collected. Two birds per replicate were killed at 24 d of age to obtain tibia samples.

3. Increasing Ca level significantly reduced the FI and body weight gain (BWG) between hatch and 10 and 24 d, especially with the phytase-supplemented diets. However, phytase supplementation of the diet containing 4 g NPP/kg improved the FI and BWG at d 10 and 24. At d 24, phytase supplementation improved feed conversion ratio (FCR) of birds that consumed diets containing high NPP. The overall FCR was better in birds offered the phytase-supplemented, medium-Ca diet.

4. There was a significant reduction in length, width and breaking strength of the tibia bone in birds fed on a diet with high Ca and low NPP. Phytase supplementation improved the tibia ash content and bone breaking strength of chicks fed on the diet containing 8 and 4 g/kg Ca and NPP, respectively. The Ca content of the tibia bone was low in birds fed on diets with 6 and 4 g/kg Ca and NPP, respectively, but this was counteracted by phytase supplementation.

5. Birds fed on diets with 4 g/kg NPP had the best carcass percentage and parts yield. Phytase supplementation to high-Ca diets significantly reduced the carcass yield of birds.

6. These results confirmed the detrimental effect of high dietary Ca on phytase activity and subsequent growth and bone development of birds, especially when NPP is in short supply.     

Efficacy of different levels of Escherichia coli phytase in broiler diets with a reduced P content

Escherichia coli-derived 6-phytase expressed in Pichia pastoris (Optiphos) was added to broiler rations with considerably reduced levels of phosphorus (by 1.5 g/kg). This experiment, performed over a five-week period, involved Ross 308 male chickens kept in battery cages. Each group was divided into 9 subgroups, each of 9 chickens (81 birds per treatment). Birds were allocated to a positive control group (I), a negative control group (II) and three phytase-supplemented groups (III-V--the diet as in group II + 250, 500 and 750 FTU Escherichia coli phytase/kg feed, respectively). The major components of starter and grower diets were corn, soybean and wheat meals. Starter and grower diets (in meal form) contained 6.73 and 6.05 g total P/kg, 4.05 and 3.46 g available P (aP)/kg, respectively, in group I, and 5.23 and 4.55 total P/kg, 2.54 g and 1.95 g aP /kg, respectively, in groups II-V. Phytase efficacy was evaluated based on performance results, carcass quality and bone mineralization. P reduction in group II decreased weight gains by 9.1% and increased feed conversion by approximately 8.4%, compared with group I. Diet supplementation with phytase in groups IV and V significantly compensated for the decrease in performance observed in group II. The differences in dressing percentage between group II and groups III and V were significant. Phosphorus reduction in the diets negatively influenced the process of bone mineralization, which was enhanced by phytase supplementation.     

The effect of microbial phytase on ileal phosphorus and amino acid digestibility in the broiler chicken

1. The study aimed to assess the effect of a commercially available microbial phytase on phytate phosphorus and total phosphorus content at the terminal ileum as well as true ileal amino acid digestibility. 2. Five diets, each containing a different plant-based feedstuff, were supplemented with microbial phytase and fed, along with a non-supplemented corresponding diet, to 28-d-old broiler chickens, Chromic oxide was used as an indigestible marker. Ileal contents were collected and analysed, along with the diets, for total phosphorus, phytate phosphorus and amino acids. 3. Endogenous phosphorus determined at the terminal ileum was 272 +/- 108 mg/kg food dry matter (mean +/- SE). Endogenous ileal amino acid flows ranged from 58 +/- 10 mg/kg food dry matter for methionine to 568 +/- 47 mg/kg food dry matter for glutamic acid. 4. Supplementation with microbial phytase resulted in a significantly greater phytate P disappearance from the terminal ileum for rice bran (17% units), but not for soyabean meal, maize, wheat or rapeseed meal. Similarly total phosphorus digestibility was significantly (P < 0.05) higher when microbial phytase was added to the rice-bran-based diet but not for any of the other feedstuffs. 5. Amino acid digestibility was significantly greater in the presence of microbial phytase for all the amino acids examined in wheat, for several of the amino acids each in maize and rapeseed meal and for one amino acid in rice bran and soyabean meal. The average increase in amino acid digestibility for those amino acids affected, was 13, 6, 10, 7 and 12% units for wheat, maize, rapeseed meal, rice bran and soyabean meal, respectively. 6. It appears that microbial phytase improves phosphorus digestibility and amino acid digestibility for certain plant-based feedstuffs.     

植酸酶和VD3协同对肉仔鸡生产性能和矿物元素利用率的影响

研究了植酸酶和ＶＤ３协同对采食低磷正常钙日粮的２１日龄肉仔鸡生产性能和矿物元素利用率的影响。结果表明：植酸酶和ＶＤ３显著提高了鸡采食量和日增重,降低了料肉比;植酸酶提高了胫骨灰分及其镁和锌含量;降低了血浆中钙含量,提高了磷和铜含量,ＶＤ３也显著提高了胫骨灰分含量,但其所含矿物元素含量不受影响;日粮中同时添加植酸酶和ＶＤ３,效果更为理想,二者产生了明显的协同效应,显著提高了矿物元素的利用率。     

Effects of citric acid and microbial phytase on amino acid digestibility in broiler chickens

1. Two experiments with growing chickens were carried out to study the effects of the inclusion of a microbial phytase (Natuphos 5000) and citric acid (CA) in maize-soybean-based diets on the performance and apparent ileal digestibility (AID) of crude protein (CP) and amino acids (AA). In both experiments the diets were formulated to contain the same amounts of energy and protein. 2. In the first experiment, data were analysed as a 2 x 2 factorial arrangement with two concentrations of available phosphorus (AP) from one day to 3 weeks of age (3.5 and 2.2 g/kg) and for 3 to 6 weeks (2.7 and 1.4 g/kg), and two inclusions of commercial phytase (0 and 500 FTU/kg) in each period. The AID of CP and dispensable and indispensable AA were not modified by the AP content of the diet. Addition of phytase improved the AID of CP and dispensable and indispensable AA only at low AP levels. 3. In the second experiment, data were analysed as a 3 x 2 factorial arrangement with three concentrations of citric acid (0, 20 and 50 g/kg) and two inclusions of commercial phytase (0 and 750 FTU/kg). Diets were formulated with deficient contents of AP (2.5 g/kg). Performance was not affected by commercial phytase addition. The addition of CA reduced the weight gain but did not modify the feed intake and gain:feed. In general, the AID of CP and dispensable and indispensable AA were not affected by CA addition. Commercial phytase increased the apparent ileal digestibility of crude protein but had no effect on AID of dispensable and indispensable AA. 4. In conclusion, the present work showed that microbial phytase enhanced AA digestibility in maize-soy-based diet only at very low AP concentrations, and that CA had no affect on the AID of CP and dispensable and indispensable AA. No synergism between CA and microbial phytase was detected.     

Influence of different phosphorus levels and phytase supplementation in gestation diets on sow performance

A total of 104 sows of different parities were studied. They were fed four diets with different phosphorus (P) levels during gestation for two reproductive cycles, while the same diet was fed during lactation. The aim was to decrease the total P level in the diet during gestation and to evaluate the effect on sow performance. The gestation treatments were low P (LP-; 3.7 g P/kg feed), low P with phytase (LP+, Ronozyme P; 765 FTU/kg feed), medium P (MP; 4.5 g P/kg feed) and high P (HP; 6.0 g P/kg feed). Daily feed allowances were 2.6 kg during gestation and 9.2 kg during lactation. Number of born piglets and piglet mortality were higher (p < 0.05) in the LP treatments than in the MP and HP treatments. No difference (p > 0.05) in the numbers of live-born piglets, piglet birthweights, sow weights or piglet weight gains was found between the treatments. Phosphorus level in sow milk was the highest (p < 0.05) in the MP treatment, while no effects (p > 0.05) of treatment were found on milk Ca levels, P and Ca levels in serum of sows and piglets, nor on the analysed mineral, fat and protein contents of piglets. The estimated average requirement of P for the entire gestation period was 4.4-4.5 g/day. In conclusion, a reduction of dietary total P content during gestation did not result in negative effects on sow or piglet performance. This suggests that it should be possible to lower the dietary P content for gestating sows, compared with earlier recommendations, and thereby reduce the environmental P pollution.     

Effect of a novel microbial phytase on production performance and tibia mineral concentration in broiler chickens given low-calcium diets

1. In a 42-d feeding trial, 264 one-d-old, as hatched, Cobb 400 broiler chickens (6 pens per group, n = 11 per pen in a 2?×?2 factorial arrangement) were fed on two concentrations of dietary calcium (Ca) (9.0 and 7.5 g/kg in starter, 7.5 and 6 g/kg in grower phases) and supplemental phytase (0 and 500 U/kg diet).

2. During d 0–21, the high Ca + phytase diet improved body weight. During d 0–42, feed intake was increased by the low Ca diet and decreased by phytase supplementation. Feed conversion ratio during d 0–21 was improved by the high Ca + phytase diet.

3. At d 42, Ca in duodenal digesta was reduced by low dietary Ca and supplemental phytase. High dietary Ca reduced P in duodenal and jejunal digesta. Phytase reduced digesta P and increased serum P concentration.

4. Relative tibia length decreased with low dietary Ca and increased with phytase. The robusticity index of tibia was improved by the low Ca diet and phytase supplementation. Phytase supplementation increased tibia ash and concentrations of Ca, magnesium (Mg), manganese (Mn), copper (Cu), zinc (Zn) and iron (Fe) in tibia. The low Ca diet increased Mg, Mn and Fe and reduced Cu and Zn in tibia.

5. It was concluded that 7.5 g Ca/kg during weeks 0–3 and 6 g Ca/kg during weeks 3–6 sustained broiler performance and bone ash, while phytase supplementation facilitated tibia mineralisation, particularly during the grower phase.     

Effects of additional zinc and phytase on zinc availability in piglets and chicks fed diets containing different amounts of phytates

Two maize based diets containing 2.3 g phytic P and 38 mg Zn/kg (P+) or 1.3 g phytic P and 25 mg Zn/kg (P−) were formulated. A third diet (P+/Phytase) was P+ supplemented with 3-phytase (500 FTU/kg). Each of these three basal diets, supplemented or not with 15 mg Zn/kg, was given during 20 days to weaned piglets and to 1-day-old chicks. Chicks fed the P− diets were removed from the data set because of an abnormally low feed intake.

In piglets, added Zn increased bone (P < 0.05) and plasma Zn (P < 0.01) irrespective of the basal diet (basal diet × Zn, P > 0.05). Supplementing P+ with phytase was more efficient in improving these indicators of Zn status than replacing P+ by P−. In chicks, supplemental Zn improved Zn status in a higher extent when added to P+ than to P+/Phytase (basal diet × Zn, P < 0.05). Phytase increased Zn status in a lesser extent than 15 ppm supplemental Zn. More Zn was soluble in gizzard than in stomach which corresponded to the differences in pH (4.2 vs 5.0). Phytase increased soluble Zn in stomach (P < 0.05) but not in gizzard. These results suggest a higher availability of Zn in chicks than in piglets in the absence of phytase. This may explain the higher efficacy of phytase for improved Zn availability in piglets than in chicks.     

Effects of ethylenediaminetetraacetic acid on phytate phosphorus utilization and efficiency of microbial phytase in broiler chicks

Previous studies have suggested that organic acids may improve P utilization in animals. To evaluate the ability of ethylenediaminetetraacetic acid (EDTA) to improve phytate P utilization and the possible synergistic effect between EDTA and microbial phytase (MP) an experiment was conducted using 360 Ross 308 broiler chicks. The experiment was carried out using a completely randomized design with a 3*2 factorial arrangement (0, 0.1 and 0.2% EDTA and 0 and 500 IU MP). Four replicate of 15 chicks per each were fed dietary treatments including (i) P-deficient basal diet [0.2% available phosphorus (aP)] (NC); (ii) NC + 500 IU MP per kilogram of diet; (iii) NC + 0.1% EDTA per kilogram of diet; (iv) NC + 0.1% EDTA and 500 IU MP per kilogram of diet; (v) NC + 0.2% EDTA per kilogram; and (vi) NC + 0.2% EDTA + 500 IU MP per kilogram of diet. Weight gain (WG), feed efficiency and serum Ca, P and alkaline phosphatase (ALP) were assessed. Addition of 0.2% EDTA to low aP diets resulted in significantly lower feed consumption (FC) and WG, but 0.1% EDTA did not depress WG compared to NC. Phytase supplementation of P-deficient diets significantly improved WG and feed efficiency, but it had no effect on FC. Microbial phytase supplementation significantly decreased ALP concentration. Results obtained in our study suggest no synergistic effect between phytase and EDTA in broiler chicks.     

低水平钙磷日粮添加植酸酶对肉鸡生长性能和养分消化的影响

文章旨在探讨植酸酶对饲喂低水平钙磷日粮肉鸡生长性能和养分表观消化率的影响.试验将平均初始体重为(61.56±0.66)g的1日龄肉鸡随机分为4组,每组4个重复,每个重复38只.对照组饲喂正常钙磷水平的玉米豆粕型日粮,T1～T3组饲喂低钙磷水平的玉米豆粕型日粮+0、1000和1500?FIU/kg植酸酶,试验分为1～21...     

The effects of phytase and phytic acid on the loss of endogenous amino acids and minerals from broiler chickens

1. The effects of myo-inositol hexaphosphate (IP6) and phytase (EC 3.1.3.26) on the excretion of endogenous compounds were investigated using growing broiler chickens. 2. A total of 32 female Ross broilers were used in a precision feeding assay involving a 2 x 2 factorial arrangement of treatments. The materials administered were glucose, glucose + 1000 units of phytase activity (FTU), glucose + 1 g of IP6 and glucose + 1 g of IP6 + 1000 FTU. Excreta were collected quantitatively over a 48-h period following intubation of the test materials. The excretion of nitrogen, amino acids, minerals, sialic acid and phytate phosphorus was determined. 3. The ingestion of 1 g of IP6 by broilers increased the excretion of endogenous nitrogen, amino acids, iron, sodium, sulphur and sialic acid compared with birds fed on glucose. Supplementation of IP6 with exogenous phytase reduced the excretion of endogenous amino acids, calcium, sodium, phytate phosphorus and sialic acid compared with birds fed IP6. 4. It can be concluded that IP6 increases the excretion of endogenous minerals and amino acids in broiler chickens. Part of the beneficial effects of the addition of exogenous phytases to the diets of poultry appears to be mediated through a reduction in endogenous losses of these nutrients.     

Effect of dietary calcium level and source on mineral utilisation by piglets fed diets containing exogenous phytase

Calcium and phosphorus are essential minerals, closely linked in digestive processes and metabolism. With widespread use of low P diets containing exogenous phytase, the optimal dietary Ca level was verified. The 40‐day study evaluated the effects of Ca level (4, 7 and 10 g/kg diet) and Ca source (Ca from CaCO₃ and from Lithothamnium calcareum) on mineral utilisation in 72 piglets (7.9 ± 1.0 kg BW) fed an exogenous phytase containing diet with 2.9 g digestible P/kg. Measured parameters were growth performance, stomach mineral solubility, bone breaking strength and urinary, serum and bone mineral concentration. The apparent total tract digestibility of minerals was also assessed in the two diets with 7 g Ca/kg, using 12 additional pigs. Regardless of Ca source, increasing dietary Ca impaired feed conversion ratio, increased urinary pH, increased serum and urinary Ca, decreased serum and urinary P, decreased serum Mg and increased urinary Mg, increased serum AP activity, decreased bone Mg increased bone Zn. Bone breaking strength was improved with 7 compared to 4 g Ca/kg. Compared to CaCO₃, Ca from Lithothamnium calcareum increased serum Mg and with, 10 g Ca/kg, it limited body weight gain. The dose response of Ca in a diet with 2.9 g digestible P/kg and including exogenous phytase indicated that: (i) a low dietary Ca was beneficial for piglet growth, but was limiting the metabolic use of P; (ii) a high dietary Ca level impaired P utilisation; (iii) the optimal P utilisation and bone breaking strength was obtained with a dietary Ca‐to‐digestible P ratio of 2.1 to 2.4:1; (iv). Increasing dietary Ca reduced Mg utilisation, but not Zn status, when fed at adequate level. Finally, Ca from Lithothamnium calcareum had similar effects on Ca and P metabolism as CaCO₃, but impaired growth when fed at the highest inclusion level.     

Effects of supplementing freeze-dried Mitsuokella jalaludinii phytase on the growth performance and gut microbial diversity of broiler chickens

Inclusion of phytase in animal feedstuff is a common practice to enhance nutrients availability. However, little is known about the effects of phytase supplementation on the microbial ecology of the gastrointestinal tract. In this study, freeze-dried Mitsuokella jalaludinii phytase (MJ) was evaluated in a feeding trial with broilers fed a low available phosphorus (aP) diet. A total of 180 male broiler chicks (day-old Cobb) were assigned into three dietary treatments: Control fed with 0.4% (w/w) of available phosphorus (aP); Group T1 fed low aP [0.2% (w/w)] supplemented with MJ; and T2 fed low aP and deactivated MJ. The source of readily available P, dicalcium phosphate (DCP), was removed from low aP diet, whereby additional limestone was provided to replace the amount of Ca normally found in DCP. For each treatment, 4 replicate pens were used, where each pen consisted of 15 animals. The animals' energy intake and caecal bacterial community were monitored weekly for up to 3 weeks. The apparent metabolizable energy (AME) and apparent digestibility of dry matter (ADDM) of broilers fed with different diets were determined. In addition, the caecal microbial diversities of broilers were assessed using high-throughput next-generation sequencing targeting the V3-V4 region of bacterial 16S rRNA. The results showed that broilers fed with T1 diet have better feed conversion ratio (FCR) when compared to the Control (p < .05) and T2 diets (p < .05), demonstrating the efficiency of MJ as a supplement to low aP diet. Nevertheless, MJ did not significantly affect the microbial population and diversity in broilers' caeca, which mainly consists of members from Bacteroidetes, Firmicutes, and Proteobacteria. Regardless, significant variations in the caecal bacterial composition were observed over time, probably due to succession as the broilers aged. This is the first reported study on the effect of MJ on the microbial diversity of broiler's caeca.     

Effects of dietary boron and phytase supplementation on growth performance and mineral profile of broiler chickens fed on diets adequate or deficient in calcium and phosphorus

1. Two experiments were designed to determine the effect of dietary boron (B) in broiler chickens. In Experiment 1, a 2 × 4 factorial arrangement of treatments was used to investigate the effect of dietary calcium (Ca) and available phosphorus (aP) (adequate or deficient) and supplemental B (0, 20, 40, and 60 mg/kg diet). In Experiment 2, B, at 20 mg/kg, and phytase (PHY) (500 FTU/kg diet) were incorporated into a basal diet deficient in Ca and aP, either alone or in combination.

2. The parameters that were measured were growth performance indices, serum biochemical activity as well as ash and mineral (i.e. Ca, P, Mg, Fe, Cu and Zn) content of tibia, breast muscle and liver.

3. Results indicated that both supplemental B and dietary Ca and aP had marginal effects on performance indices of chickens grown for 42 d.

4. There were positive correlations (linear effect) between B concentrations of serum, bone, breast muscle and liver and the amount of B consumed.

5. Serum T₃ and T₄ activities increased linearly with higher B supplementation.

6. Increasing supplemental B had significant implications on breast muscle and liver mineral composition. Lowering dietary Ca and aP level increased Cu content in liver and both Fe and Zn retention in breast muscle. Tibia ash content and mineral composition did not respond to dietary modifications with either Ca–aP or B.

7. The results also suggested that dietary contents of Ca and aP do not affect the response to B regarding tissue mineral profile. Dietary combination with B and PHY did not create a synergism with regard to growth performance and bioavailability of the minerals.     

Effects on performance of growing pigs fed diets containing different levels of dried cashew pulp

The purpose was to investigate the use of dried cashew pulp (DrCP), the sun-dried residue after juice has been extracted from the cashew apple, as a feed ingredient in growing pig diets. The growth rate, feed intake, feed to gain ratio and cost of gain of grower pigs fed diets containing 0 (0DrCP), 100 (100DrCP), 150 (150DrCP) or 200 (200DrCP) g kg⁻¹ of dried cashew pulp was investigated in a feeding trial set up as a Completely randomized design with 4 treatments replicated 3 times and lasting 112 days. There were no significant differences (P > 0.05) among treatments in the parameters measured. It was concluded that dried cashew pulp could be used in growing pig diets up to a level of 200 g kg⁻¹ without any deleterious effects. Future work will look at higher levels of DrCP inclusion in the diets of growing pigs.     

Performance, carcass characteristics, meat quality and plasma constituents of meat type drakes fed diets containing different levels of lysine with or without a microbial phytase.

This experiment was conducted to study growth performance, carcass characteristics, meat quality and plasma constituents of Campbell drakes fed diets containing different levels of lysine with or without a microbial phytase. Basal vegetable duck all-mash diets were fed during the growing (1-35 d of age), and finishing period (36-56 d of age) and were formulated to contain 0.90% and 0.73% lysine (negative control), respectively. These diets were supplemented or not with L-lysine HCl, which resulted in a dietary lysine level of 0.90, 0.95, 1.01 and 1.06% and 0.73, 0.80, 0.87 and 0.94%, during the growing and finishing period, respectively. Furthermore, the diets were fed with or without 600 FTU phytase (Natuphos) except for those containing 1.06 and 0.94% lysine during the growing and finishing period, respectively (positive control). A lysine level of 1.01/0.87% in the growing/finishing diet significantly increased BWG and improved FCR of drakes by 2.1 and 1.8%, respectively. Phytase significantly increased BWG by 2.1% and 3.5% after feeding the basal diet and 1.01/0.87% lysine, respectively. Also, FCR was significantly improved by 2.2 and 1.8% of groups fed 0.95/0.80, and 1.01/0.87% lysine, respectively. Phytase as an independent variable increased BWG by 1.8, and improved FCR by 1.0%. Lysine and/or phytase did not affect carcass yield, and meat quality treats as well as plasma constituents of drakes. However, lysine level at 0.95/0.80% and 1.01/0.87% significantly decreased abdominal fat deposition compared to either the negative or the positive control. In conclusion, a lysine level of 1.01/0.87% in the growing/finishing diets for drakes is adequate. After phytase supplementation of the basal diet the BWG at a lysine level of 0.90/0.73% were similar to the positive control (1.06/0.94% lysine). However, the best FCR was obtained after feeding diets containing 1.01/0.87% lysine supplemented with phytase.     

添加不同水平有机硒对红羽肉鸡生长和饲料报酬的影响

本试验通过研究蛋氨酸硒(Se-Met)对红羽肉仔鸡生产性能、饲料报酬的影响来探讨红羽肉仔鸡有机硒(蛋氨酸硒)的适宜添加量.选择1日龄红羽肉雏鸡180只,分为4组,分别饲喂在玉米-豆粕型基础日粮中分别添加蛋氨酸硒0、0.1、0.3、0.5 mg/kg的试验日粮.试验结果表明:在0～21日龄,0.1 mg/kg的蛋氨酸硒添加量效果最好,可提高日增重17.29%;不同蛋氨酸硒添加水平对红羽肉仔鸡胴体特性无显著影响(P＞0.05);可显著提高红羽内仔鸡的胸肌率与腿肌率(P＜0.05),降低红羽肉鸡的皮下脂肪厚与肌间脂肪宽.     

Effects of microbial phytase on growth and mineral utilisation in broilers fed on maize soyabean-based diets.

1. A 3-week feeding trial with 96 sexed d-old broiler chickens was conducted to examine the effects of microbial phytase supplementation (Natuphos 5000) at 2 dietary energy concentrations on their performance, and the utilisation of nitrogen (N), phosphorus (P), calcium (Ca) and zinc (Zn) and on tibiae ash, Ca, P and Zn concentrations. Four replicate pens (6 birds per pen) of a completely randomised design were used in a 2x2 factorial arrangement of treatments with 2 contents of metabolisable energy (11.72 and 12.55 MJ ME/kg) and 2 additions of phytase (0 and 500 U of microbial phytase/kg). 2. Phytase supplementation significantly improved the utilisation of N, P, Ca and Zn (as a percentage of intake) and increased the concentration of Ca and Zn in the tibiae (P<0.05) because of higher intakes of dry matter, N, P, Ca and Zn. Phytase also significantly reduced the amount of P in the excreta (P<0.05). 3. The AME content of the diet influenced significantly (P<0.05) the excretion of N, P, Ca and Zn and the concentration of P and Ca in tibiae with the birds fed on the high AME diet excreting more minerals and having a smaller percentage of these minerals in their tibiae. However, there were strong interactions between phytase addition and AME in tibia ash and P, with the phytase supplementation producing a higher ash content at the higher AME a and a lower P content at the lower AME.