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SUMMARY: This experiment was conducted to investigate the effect of phytase supplementation in diets reduced in amino acids (AA), crude protein (CP), and phosphorus (P) on growth performance, carcass traits, and tibia ash of broiler chickens. A total of 2,240 unsexed Ross 308 broiler chickens were used in 56 floor pens with 40 birds each and fed one of eight dietary treatments in seven replicates until 35 d of age. A positive control (PC) diet and diets with dietary AA/CP level reduced by 2, 4, and 6% were used with and without supplementation with 1,500 FTU phytase/kg. Starter, grower, and finisher diets were fed from d 1 to 10, d 10 to 25, and d 25 to 35, respectively. For the total period, no significant interaction effects between AA/CP level and phytase supplementation were detected for any measured traits. The ADG, ADFI, carcass weight, breast weight, and tibia ash weight were lower and FCR was higher compared to the PC diets when the AA/CP level was reduced by more than 2%. Phytase supplementation increased ADG, ADFI, final BW, and tibia ash weight. Tibia ash measurements showed that birds were adequately supplied with digestible phosphorus in all treatments, although dietary phosphorus and calcium were reduced in the phytase-supplemented diets. This enabled the feeding of broiler chickens without mineral phosphate supplements in grower and finisher diets. The results showed that supplementation with 1,500 FTU phytase/kg diminished the growth-decreasing effect of lower dietary AA/CP at all reduction steps.

Summary: The objective was to evaluate the effects of different levels of phytase in diets with varying amounts of phytate on live performance and bone characteristics of broiler chickens at 21 D. The treatments consisted of a 3 × 5 factorial arrangement, with 3 levels of phytate, high (HP), medium (MP), and low (LP), and 5 diets consisting of a positive control (PC); negative control (NC, with a reduction of 0.15% of calcium [Ca] and 0.15% of phosphorus [P]), and NC diet plus 0, 500, 1,000, or 1,500 FTU kg−1 of phytase. Feed intake peaked with supplementation of 1,051 FTU kg−1 phytase to the LP diets. Bone ash of broilers receiving LP showed a maximum response at 1,101 FTU kg−1. Birds receiving the NC diet had a larger hypertrophic cartilage zone (P < 0.05) than those receiving the PC diet. Serum Ca and P of birds receiving the NC treatment and LP diet were lower than those in broilers fed with the MP and HP diets. Broilers in the NC plus 500 FYT kg−1 treatments had lower tibia P levels than those in the PC treatment; also, broilers receiving HP diets had a higher tibia Ca content than those receiving LP diets (P < 0.05). In general, bone P of birds fed with diets containing HP was higher than that of birds on a LP or MP diet (P < 0.05). The use of 1,101 FTU kg−1 resulted in better bone characteristics when fed with the lowest phytate level, and this level does not negatively affect the other parameters evaluated.

SUMMARY: Like other poultry species, Pekin ducks may develop gait abnormalities due to increased muscle growth relative to the skeletal system. Previous studies have shown that Pekin leg bones grow exponentially in terms of mineral deposition during the first 2 wk of life. Therefore, we hypothesized that a slight food restriction (FR) during that time would reduce muscle mass development sufficiently to allow the skeletal system to more fully develop. Our primary goal was to determine if FR could occur without increasing the time to market weight. To obtain this goal, ducks were provided either 65% (FR65) or 85% (FR85) of the control ducks daily feed intake. Food restricted ducks had lower (P < 0.05) body weights than controls at days 7 and 14. After day 14, when all ducks were fed ad libitum (ad libitum), food restricted ducks ate significantly (P < 0.01) more feed per day than control ducks and subsequently gained body weight at an increased rate. By day 35 there were no significant differences in body weight between FR85 and controls, however both FR groups showed reduced (P < 0.05) breast mass compared to controls. Qualitative assessment of gait also suggested that FR ducks had more uniform leg conformation and gait then did the control ducks and did not show any biological signs of reduced welfare. These data suggest that a slight FR is possible without adding time to market and this paradigm might reduce the occurrence of lameness in growing ducks.

Aluminum doped magnetite (Fe3O4) magnetic nanoparticle (MNP) has been used as an effective sorbent to remove phosphorus (P) species in poultry processing wastewaters. It was found that spent MNP contains approximately 13% of P by weight. A study was conducted to evaluate the potential of using spent MNP as a P source. A total of 240 one-day-old male broilers were randomly allocated to four dietary treatments and six replicate each for 18 days. Treatments consisted of 1) positive control (PC) with 0.45% nonphytate-P (nPP); 2) negative control (NC) with a reduction of 0.15% nPP; 3) NC with additional 0.075% of P from magnetic nanoparticle (NC + 0.075% P-MNP); and 4) NC with additional 0.15% of P from magnetic nanoparticle (NC + 0.15% P-MNP). Body weight and feed intake were recorded at day 7, 14, and 18. Three birds were randomly selected from each cage for Dual-energy X-ray Absorptiometry (DXA) scanning at d18. The liver, heart, and spleen were collected and analyzed for mineral content. Ileal digesta were collected from the rest of the birds for P digestibility analysis. Data were subjected to SAS using one-way ANOVA model with GLM procedure. The birds fed with additions of 0.075% and 0.15% P from MNP had an increased (P = 0.017) body weight gain at d8 to d14 compared to those with NC diet. Significant lower (P ≤ 0.008) body mineral density and body mineral content were observed in the birds with NC diet compared to those with PC, NC + 0.075% P- magnetic nanoparticle, and NC + 0.15% P- magnetic nanoparticle diets. In addition, the birds with NC + 0.075% P- magnetic nanoparticle and NC + 0.15% P- magnetic nanoparticle had similar body mineral contents and body mineral densities compared to the PC-fed birds, indicating P from spent magnetic nanoparticle has incorporated into the bone mineralization. No significant differences were found between the treatments for mineral residues (Al and Fe) in liver, heart and spleen samples. The ileal P digestibility of dry matter and P was not influenced by the presence of magnetic nanoparticle in diets. In conclusion, 0.15% P from spent magnetic nanoparticle could be efficiently and safely used to replace the same amount P from dicalcium phosphate in the diets for broilers. [ABSTRACT FROM AUTHOR]

Summary: Aluminum doped magnetite (Fe3O4) magnetic nanoparticle (MNP) has been used as an effective sorbent to remove phosphorus (P) species in poultry processing wastewaters. It was found that spent MNP contains approximately 13% of P by weight. A study was conducted to evaluate the potential of using spent MNP as a P source. A total of 240 one-day-old male broilers were randomly allocated to four dietary treatments and six replicate each for 18 days. Treatments consisted of 1) positive control (PC) with 0.45% nonphytate-P (nPP); 2) negative control (NC) with a reduction of 0.15% nPP; 3) NC with additional 0.075% of P from magnetic nanoparticle (NC + 0.075% P-MNP); and 4) NC with additional 0.15% of P from magnetic nanoparticle (NC + 0.15% P-MNP). Body weight and feed intake were recorded at day 7, 14, and 18. Three birds were randomly selected from each cage for Dual-energy X-ray Absorptiometry (DXA) scanning at d18. The liver, heart, and spleen were collected and analyzed for mineral content. Ileal digesta were collected from the rest of the birds for P digestibility analysis. Data were subjected to SAS using one-way ANOVA model with GLM procedure. The birds fed with additions of 0.075% and 0.15% P from MNP had an increased (P = 0.017) body weight gain at d8 to d14 compared to those with NC diet. Significant lower (P ≤ 0.008) body mineral density and body mineral content were observed in the birds with NC diet compared to those with PC, NC + 0.075% P- magnetic nanoparticle, and NC + 0.15% P- magnetic nanoparticle diets. In addition, the birds with NC + 0.075% P- magnetic nanoparticle and NC + 0.15% P- magnetic nanoparticle had similar body mineral contents and body mineral densities compared to the PC-fed birds, indicating P from spent magnetic nanoparticle has incorporated into the bone mineralization. No significant differences were found between the treatments for mineral residues (Al and Fe) in liver, heart and spleen samples. The ileal P digestibility of dry matter and P was not influenced by the presence of magnetic nanoparticle in diets. In conclusion, 0.15% P from spent magnetic nanoparticle could be efficiently and safely used to replace the same amount P from dicalcium phosphate in the diets for broilers.

Summary: An experiment was conducted to evaluate the effects of phytase and multicarbohydrase (MC) on growth performance, bone ash, and nutrient digestibility in broilers fed a nutritionally reduced diet. A total of 480 Cobb 500 male broilers were randomly allocated to 8 treatments with 6 replicates of 10 birds each. Experimental diets consisted of a positive control (PC); a negative control (NC) with the reduction of ME, CP, Ca, and nonphytate phosphorus by 75 kcal/kg, 1.5, 0.15, and 0.15%, respectively; NC plus phytase at 500, 1,000, or 1,500 FTU/kg as T3–T5; and further plus MC at 500 mg/kg as T6–T8. Results showed that during 0–18 d of age, feed conversion ratio (FCR) was increased (P

Summary: An experiment was conducted to evaluate high doses of phytase associated with multicarbohydrase complex in diets with a nutritional reduction on feed cost, performance, intestinal morphometry, digesta viscosity, blood and bone parameters, and carcass yield of broilers. For this purpose, 1,540 1-day-old male broiler chicks were distributed in a completely randomized design with 5 treatments, with 14 replicates and 22 birds each. The treatments consisted of the following: positive control (PC), a diet meeting the nutritional requirements without enzymes; negative control (NC), a PC diet with a reduction of 100 kcal/kg AME, 0.15% available P, 0.12% Ca, 4% digestible lysine, and 5% Na; NC diet + multicarbohydrase complex (MCC) + phytase at 3 levels (1,000, 1,500, and 2,000 FTU/kg). The results demonstrated that the use of phytase associated with MCC in nutrient-restricted diets maintained broiler performance in the prestarter phase. From 1 to 42 d, broilers fed enzyme-supplemented diets had a better performance than those receiving nutrient-restricted diets without enzymes. The different levels of phytase associated with MCC affected the serum biochemical parameters of broilers; however, these modifications did not influence bone characteristics. The mode of action of enzymes is substrate-dependent, which may have limited enzyme activity. As a result, no improvements in carcass yield or intestinal and bone parameters were observed. It is concluded that diets with nutritional reduction and addition of 1,000 FTU/kg phytase in association with MCC maintain the performance and is a feasible strategy to reduce feed cost.

An experiment was conducted to evaluate high doses of phytase associated with multicarbohydrase complex in diets with a nutritional reduction on feed cost, performance, intestinal morphometry, digesta viscosity, blood and bone parameters, and carcass yield of broilers. For this purpose, 1,540 1-day-old male broiler chicks were distributed in a completely randomized design with 5 treatments, with 14 replicates and 22 birds each. The treatments consisted of the following: positive control (PC), a diet meeting the nutritional requirements without enzymes; negative control (NC), a PC diet with a reduction of 100 kcal/kg AME, 0.15% available P, 0.12% Ca, 4% digestible lysine, and 5% Na; NC diet 1 multicarbohydrase complex (MCC) 1 phytase at 3 levels (1,000, 1,500, and 2,000 FTU/kg). The results demonstrated that the use of phytase associated with MCC in nutrient-restricted diets maintained broiler performance in the prestarter phase. From 1 to 42 d, broilers fed enzyme-supplemented diets had a better performance than those receiving nutrient-restricted diets without enzymes. The different levels of phytase associated with MCC affected the serum biochemical parameters of broilers; however, these modifications did not influence bone characteristics. The mode of action of enzymes is substrate-dependent, which may have limited enzyme activity. As a result, no improvements in carcass yield or intestinal and bone parameters were observed. It is concluded that diets with nutritional reduction and addition of 1,000 FTU/kg phytase in association with MCC maintain the performance and is a feasible strategy to reduce feed cost. [ABSTRACT FROM AUTHOR]

An experiment was conducted to evaluate the effects of phytase and multicarbohydrase (MC) on growth performance, bone ash, and nutrient digestibility in broilers fed a nutritionally reduced diet. A total of 480 Cobb 500 male broilers were randomly allocated to 8 treatments with 6 replicates of 10 birds each. Experimental diets consisted of a positive control (PC); a negative control (NC) with the reduction of ME, CP, Ca, and nonphytate phosphorus by 75 kcal/kg, 1.5, 0.15, and 0.15%, respectively; NC plus phytase at 500, 1,000, or 1,500 FTU/kg as T3-T5; and further plus MC at 500 mg/kg as T6-T8. Results showed that during 0-18 d of age, feed conversion ratio (FCR) was increased (P, 0.05) in the NC group compared with the PC group; this was recovered (P, 0.05) in T5 group; BW gain (BWG) was increased (P, 0.05) in T6-T8, and FCR was decreased (P, 0.05) in T6 and T8, compared with the NC group. For bone mineralization, fat-free dry weight, weight, percentage, and concentration of tibia ash were decreased (P, 0.05) in the NC group compared with the PC group; T3-T5 increased (P, 0.05) tibia ash percentage and concentration, compared with the NC group, but only the tibia ash percentage reached to the level that of the PC group; T6-T8 increased (P, 0.05) tibia ash weight, percentage, and concentration compared with the NC group. Similarly, nitrogen retention and AMEn were decreased (P, 0.05) in the NC group and recovered in T3-T8; ileal P digestibility also was increased in T3-T8, to a greater level than that in the PC group. The results from contrasts suggested increasing phytase level with or without carbohydrase linearly increased broiler BWG, FCR, bone mineralization, N retention, and ileal P digestibility. Moreover, when combined with carbohydrase, increased phytase level in the diet linearly increased broiler energy utilization, while phytase alone showed no effect on AMEn. In conclusion, supplementation of a combination of phytase and MC could compensate the decreases in growth performance, bone ash, and nutrient digestibility caused by a nutritionally reduced diet. [ABSTRACT FROM AUTHOR]

Summary: An experiment was conducted to evaluate the effects of dietary nonphytate phosphorus level and a novel corn-expressed phytase (GraINzyme, Agrivida Inc., Woburn, MA) supplementation on broiler growth performance and bone mineralization. Broilers were fed graded levels of nonphytate phosphorus from 0.20 to 0.44% increased by 0.06% and 4 levels of corn-expressed phytase (500; 1,500; 3,000; and 4,500 FTU/kg). Dicalcium phosphate was used as the reference for inorganic phosphorous. Increasing dietary nonphytate phosphorus level or supplementation of phytase linearly (P < 0.01) increased the bodyweight gain, feed intake, tibia fat–free dry weight, ash weight, ash percentage, and ash concentration. Feed conversion ratio was linearly (P < 0.01) improved as the dietary nonphytate phosphorus level was gradually increased. Graded nonphytate phosphorus levels were log-transformed and regressed against the bodyweight gain, tibia ash weight, ash percentage, and ash concentration for calculating the nonphytate phosphorus relative to the phytase efficacy. Both raw and standardized responses were regressed against dietary nonphytate phosphorus levels. Bodyweight gain was less sensitive than bone mineralization results. From the regression estimates using standardized responses, bodyweight gain was about 92% of tibia ash concentration in terms of sensitivity. The calculated nonphytate phosphorus relative to the equivalence for bodyweight gain, tibia ash weight, ash percentage, and ash concentration were 0.166, 0.158, 0.163, and 0.183%, respectively. Results suggest that the corn-expressed phytase is effectively released in the P form phytate and improves broiler growth performance and bone mineralization. Bone mineralization is a better indicator for the broiler response to dietary nonphytate phosphorus levels than bodyweight gain.

The objective was to evaluate the effects of different levels of phytase in diets with varying amounts of phytate on live performance and bone characteristics of broiler chickens at 21 D. The treatments consisted of a 3 3 5 factorial arrangement, with 3 levels of phytate, high (HP), medium (MP), and low (LP), and 5 diets consisting of a positive control (PC); negative control (NC, with a reduction of 0.15% of calcium [Ca] and 0.15% of phosphorus [P]), and NC diet plus 0, 500, 1,000, or 1,500 FTU kg21 of phytase. Feed intake peaked with supplementation of 1,051 FTU kg21 phytase to the LP diets. Bone ash of broilers receiving LP showed a maximum response at 1,101 FTU kg21. Birds receiving the NC diet had a larger hypertrophic cartilage zone (P, 0.05) than those receiving the PC diet. Serum Ca and P of birds receiving the NC treatment and LP diet were lower than those in broilers fed with the MP and HP diets. Broilers in the NC plus 500 FYT kg21 treatments had lower tibia P levels than those in the PC treatment; also, broilers receiving HP diets had a higher tibia Ca content than those receiving LP diets (P, 0.05). In general, bone P of birds fed with diets containing HP was higher than that of birds on a LP or MP diet (P, 0.05). The use of 1,101 FTU kg21 resulted in better bone characteristics when fed with the lowest phytate level, and this level does not negatively affect the other parameters evaluated. [ABSTRACT FROM AUTHOR]

Like other poultry species, Pekin ducks may develop gait abnormalities due to increased muscle growth relative to the skeletal system. Previous studies have shown that Pekin leg bones grow exponentially in terms of mineral deposition during the first 2 wk of life. Therefore, we hypothesized that a slight food restriction (FR) during that time would reduce muscle mass development sufficiently to allow the skeletal system to more fully develop. Our primary goal was to determine if FR could occur without increasing the time to market weight. To obtain this goal, ducks were provided either 65% (FR65) or 85% (FR85) of the control ducks daily feed intake. Food restricted ducks had lower (P < 0.05) body weights than controls at days 7 and 14. After day 14, when all ducks were fed ad libitum (ad libitum), food restricted ducks ate significantly (P < 0.01) more feed per day than control ducks and subsequently gained body weight at an increased rate. By day 35 there were no significant differences in body weight between FR85 and controls, however both FR groups showed reduced (P < 0.05) breast mass compared to controls. Qualitative assessment of gait also suggested that FR ducks had more uniform leg conformation and gait then did the control ducks and did not show any biological signs of reduced welfare. These data suggest that a slight FR is possible without adding time to market and this paradigm might reduce the occurrence of lameness in growing ducks. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effect of the combination of extra-dosing phytase and multi-carbohydrase (MC) on growth performance and bone mineralization in broilers. A total of 640 one-day-old Cobb male broilers were randomly allocated to 8 dietary treatments (4 replicates with 20 birds each) consisting of positive control (PC); negative control (NC; −0.15% Ca and non-phytate-P (nPP)); NC with phytase (500, 1000, and 1500 FTU/kg) with or without MC (500 mg/kg). Feed intake, BW, and FCR were measured at days 7, 21, and 35. At day 35, 3 birds per pen were euthanized to measure body composition using dual-energy X-ray absorptiometry, and right femurs were collected for bone ash. Supplementation of 1000 and 1500 FTU/kg of phytase improved BWG (P < 0.05) from days 0 to 7 compared to NC. There were no differences in BWG, FI and FCR during periods 0–21 d and 0–35 days respectively. NC birds had reduced (P < 0.05) body mineral density, body mineral content, femur ash weight, femur ash percentage, and femur ash concentration compared to PC while phytase at 1,000 or 1,500 FTU/kg, and phytase plus MC restored these metrics to the same levels as PC birds. The results indicate that bone mineralization parameters are more sensitive to evaluate the P sufficiency, and extra-dosing phytase or combined phytase with MC could improve phytate-P release and bone health in broiler chickens. [ABSTRACT FROM AUTHOR]

The objective of this study was to access/identify the effects of phosphorus (P) restriction as a result of non-inclusion of monocalcium phosphate on broiler's diet after 21 d of age and the use of high doses of phytase (PHY). Broilers were divided into 4 treatments: positive control (PC), with phosphate inclusion; with phytase (WPHY), a reduction of 0.15% of available P and calcium (Ca) with the inclusion of 1,000 FYT; and 2 treatments with P restriction starting at 21 d of age: Without phosphate (WoP) and without phosphate supplemented with 4,000 FYT PHY (WoP+4000 FYT). Broilers performance (WG, FI, and FCR) and bone characteristics (bone weight, mineral residue, and Ca and P ratio) were assessed at 41 d of age. In relation to performance, the exclusion of monocalcium phosphate from the diet resulted in worse WG and FCR. However, the inclusion of higher PHY dose (WoP+4000 FYT) overcame the mineral deficiency, and performance was similar to treatments that met bird's mineral requirements (PC and WPHY). The treatment with mineral restriction (WoP) had the worst results in every bone quality assessment. However, broilers of WoP+4000 FYT group had bone parameters similar to PC and WPHY. Therefore, removing phosphate in grower and finishing phases has negative impacts on broiler's performance and bone conformation, but adding high phytase dosage (4,000 FYT) overcome this damages. [ABSTRACT FROM AUTHOR]

An experiment was conducted to assess the most appropriate bone type for measuring bone mineralization in male broiler chicks up to 42 d. A total of 72 male broilers were raised in 0.64 m2 pens on a litter floor. The study design included 2 dietary treatments (Control and Low) containing differing levels of total phosphorus (7.8 and 4.4 g/kg for Control and Low diets respectively) and calcium (22.7 and 13.1 g/kg for Control and Low diets respectively) with each fed to 6 replicate pens of 6 birds. Each wk, 6 birds per diet were euthanized and leg bones removed to measure ash percentage. Foot, toe, tibia, and femur ash were compared using the mean of both legs from each bird, via t-tests to separate Control and Low diets. At the end of wk 1, diets could not be separated using any of the bone ash measures. From wk 2 to wk 5, both tibia and foot ash differentiated between the Control and Low diets, and tibia continued to show significant differences between the diets into wk 6. Femur ash did not show any dietary differences until wk 3, but then showed significant differences between the diets until wk 6. Toe ash only differentiated between diets at wk 2, and variation both within and between birds was high, particularly with younger birds. These results suggest that bird age has implications when choosing a bone for assessing possible differences in dietary phosphorus and calcium uptake. Femur ash may be more appropriate for showing differences in broilers aged 6 wk and older. Foot ash provides a comparable alternative to tibia ash in birds aged 2 to 5 wk of age, providing a labor- and time-saving alternative. [ABSTRACT FROM AUTHOR]

Feeding poultry litter biochar (PLB), a product resulting from litter gasification, could decrease diet cost, maintain broiler growth performance, and decrease land application of manure. Past research observed improved pellet quality and mineral availability with dietary inclusions of 6 to 7% PLB; however, broiler performance was decreased, likely due from toxic-heavymetal content (e.g., 99 ppm arsenic) and increased digesta viscosity of the particular PLB. The objective of the current study was to assess lower dietary inclusions of PLB, with decreased toxic-heavy-metal content, on descriptive feed manufacture, broiler performance, digesta viscosity, bone mineralization, and apparent ileal amino acid digestibility (AIAAD). Treatments were arranged as a Diet Formulation x Phytase Addition factorial in a randomized complete block design with 8 replications per treatment. Four dietary formulations were produced: positive control (PC) with 0.45% non phytate phosphorus (nPP), negative control with 0.23% nPP, and 2 or 4% PLBwith 0.45% nPP. Phytasewas either included at 9,500 ftu/kg or withheld. There were 8 treatments total. Contrasts comparing PC and 2 or 4% PLB also were conducted. Diets were pelleted and crumbled prior to feeding. Positive and negative control formulations and phytase addition affected bird performance as expected. Birds fed 2% PLB had increased FCR and birds fed 4% PLB had decreased LWGwhen compared to PC (P<0.05). However, these performance deficiencies were corrected with phytase inclusion. Birds fed diets with PLB had similar tibia measures compared to the PC. No significant main effects, interactions, or contrast comparisons were observed for viscosity data. The incorporation of PLB into formulations without phytase increased diet AIAAD of some amino acids relative to the corresponding PC (P<0.05). A lower toxic-heavy-metal PLB product (e.g., 22 ppm arsenic) provided available minerals and amino acids to diets, but performance similar to PC necessitated the addition of phytase. [ABSTRACT FROM AUTHOR]

This experiment was conducted to investigate the effect of phytase supplementation in diets reduced in amino acids (AA), crude protein (CP), and phosphorus (P) on growth performance, carcass traits, and tibia ash of broiler chickens. A total of 2,240 unsexed Ross 308 broiler chickens were used in 56 floor pens with 40 birds each and fed one of eight dietary treatments in seven replicates until 35 d of age. A positive control (PC) diet and diets with dietary AA/CP level reduced by 2, 4, and 6% were used with and without supplementation with 1,500 FTU phytase/kg. Starter, grower, and finisher diets were fed from d 1 to 10, d 10 to 25, and d 25 to 35, respectively. For the total period, no significant interaction effects between AA/CP level and phytase supplementation were detected for any measured traits. The ADG, ADFI, carcass weight, breast weight, and tibia ash weight were lower and FCR was higher compared to the PC diets when the AA/CP level was reduced by more than 2%. Phytase supplementation increased ADG, ADFI, final BW, and tibia ash weight. Tibia ash measurements showed that birds were adequately supplied with digestible phosphorus in all treatments, although dietary phosphorus and calcium were reduced in the phytase-supplemented diets. This enabled the feeding of broiler chickens without mineral phosphate supplements in grower and finisher diets. The results showed that supplementation with 1,500 FTU phytase/kg diminished the growth-decreasing effect of lower dietary AA/CP at all reduction steps. [ABSTRACT FROM AUTHOR]

A study was conducted to evaluate the effects of phytase supplementation on growth performance, phosphorus availability, and bone mineralization in broilers. Three hundred fifty Cobb × Cobb 500 slow-feathering male broilers were placed in steel battery cages into 7 treatments with 10 replications of 5 chicks each. The treatments were: a positive control (PC) diet [0.42% nonphytate phosphorus (nPP)], 4 diets containing increases in nPP from dicalcium phosphate (0.14, 0.20, 0.26, and 0.32%), and 2 phytase supplemental levels [500 and 1,000 phytase units (FYT)/kg] on the diet having 0.14% nPP. All diets contained 0.8% calcium. Growth performance and bone data were regressed against the 4 diets having increased nPP. The equations generated were replaced by the corresponding performance obtained with 2 phytase levels to estimate their nPP bioequivalence. An overall reduction in performance and bone mineralization was observed associated with a reduction in nPP. Linear fits provided the best adjustments for all responses with the exceptions of BW gain (BWG) and feed intake (FI). Adding phytase to the 0.14% nPP diet improved growth performance and bone mineralization (P < 0.001). Average bioequivalence nPP for each phytase level was dependent on the evaluated response with lowest and highest values at 500 FYT supplementation of 0.077 and 0.145 for toe P and femur Ca, respectively, whereas lowest and highest values at 1,000 FYT of 0.143 and 0.194 for BWG and toe ash. Averaging all values for 500 and 1,000 FYT provided estimations of 0.100 and 0.166 nPP, respectively. [ABSTRACT FROM AUTHOR]