Effects of Broiler Strain, Dietary Nonphytate Phosphorus, and Phytase Supplementation on Chick Performance and Tibia Ash

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1 2006 Poultry Science Association, Inc. Effects of Broiler Strain, Dietary Nonphytate Phosphorus, and Phytase Supplementation on Chick Performance and Tibia Ash M. E. Persia and W. W. Saylor 1 Department of Animal and Food Sciences, 044 Townsend Hall, 531 S. College Ave., University of Delaware, Newark, DE Primary Audience: Nutritionists, Researchers, Production Managers SUMMARY Three experiments were conducted to study the effects of broiler strain and phytase supplementation on chick nonphytate P (NPP) requirements for growth, feed intake, and tibia ash. The first experiment compared the NPP requirements for 8- to 22-d-old chicks from 2 broiler strains, Ross 308 and 708, that have been selected for differences in early weight gain and performance. The second experiment utilized similar 8- to 22-d-old Ross 308 and 708 chicks but also compared the effects of dietary fungal phytase supplementation (600 U/kg) on broiler NPP requirements. The third experiment utilized a younger starting age, 5 to 23 d old, for Ross 308 and 708 chicks with and without phytase supplementation. Minor differences in chick growth did not affect chick NPP requirements in Experiments 1 and 3, but a substantial and unexplained reduction of growth of the Ross 708 chicks in Experiment 2 resulted in a lower NPP requirement for chick growth and feed intake but not for tibia ash. As expected, supplementation of diets with fungal phytase did result in decreased NPP requirements for growth, feed intake, and tibia ash in both strains used in Experiment 3. Key words: nonphytate phosphorus requirement, phytase, broiler strain, chick performance, tibia ash 2006 J. Appl. Poult. Res. 15:72 81 DESCRIPTION OF PROBLEM Environmental concerns regarding land application of poultry litter have moved the poultry industry to review P management strategies. Currently, land application of poultry litter onto nearby fields is the most economical method of litter disposal available to poultry growers. Environmental problems arise when the nutrient content of litter applied to the land is greater than growing crops can remove or when nutrients are lost from the fields before crops can incorporate them into vegetative material (i.e., nutrient run- off into waterways) [1, 2, 3, 4, 5]. Because there are few viable alternatives to land application of poultry litter, methods to reduce litter or excreta nutrients have been explored. The commercial production of phytase has allowed industry nutritionists to reduce the total amount of P in poultry rations by liberating P bound to phytate and permitting for the reduction of supplemental inorganic sources of P, such as rock phosphate or dicalcium phosphate [6, 7, 8]. For phytase supplementation to be environmentally and economically effective, dietary concentrations of P 1 Corresponding author: bsaylor@udel.edu

2 PERSIA AND SAYLOR: BROILER STRAIN AND PHOSPHORUS USE 73 Table 1. Composition of basal diets used in Experiments 1 to 3 1 Experiment 1 Experiment 2 Experiment 3 Item (%) (%) (%) Ingredient Ground corn Soybean meal (48%) Soybean oil Ground limestone Dicalcium phosphate Salt Vitamin mix Trace mineral mix DL-Methionine Choline chloride, 60% Composition CP, calculated CP, analyzed ME n (kcal/kg) 3,272 3,253 3,272 Ca, calculated Ca, analyzed P, calculated P, analyzed Phytate P, calculated Nonphytate P, calculated Ground limestone, dicalcium phosphate and cellulose were added to basal diets to provide 23% CP, 3,200 kcal of ME n, 1.00% Ca and appropriate concentration of nonphytate P for experimental diets. 2 Provided per kilogram of diet: vitamin A (as retinyl acetate), IU; vitamin D 3 (as cholecalciferol), 4,960 ICU; vitamin E (as DL-α-tocopheryl acetate), 50 IU; riboflavin, 17 mg; niacin (as nicotinic acid), 66 mg; D-pantothenic acid (as calcium pantothenate); 23 mg; vitamin K (as menadione sodium bisulfite), 3.0 mg; folic acid, 2.0; pyridoxine (as pyridoxine hydrochloride), 5.8 mg; thiamine (as thiamine mononitrate), 4.1 mg; selenium (as Na 2 SeO 3 ), 0.3 mg; D-biotin, 0.13 mg. 3 Provided per kilogram of diet: manganese, 60 mg from manganous oxide; zinc, 57.5 mg from zinc oxide; iron, 20 mg from iron carbonate; calcium, 5 mg from calcium carbonate; copper, 2.5 mg from copper oxide; iodine, mg from ethylene diamine dihydroiodide; cobalt, 0.05 mg from cobalt carbonate. must be reduced, as currently recommended [9, 10, 11, 12]. Because of the reduced NPP concentrations being recommended, it is important to have accurate NPP recommendations for modern broiler strains. Previous research has shown that bird growth rate influences the NPP requirement of poultry. In most of this research, the effects of bird strain on NPP requirements were determined by comparing fast-growing broiler strains and slower-growing egg-laying strains [13, 14, 15, 16, 17]. Most broiler strains grow at a similar rate and have similar NPP requirements [18, 19]. However, Orban and Roland [20] did show increases in weight gain, feed intake, bone weight, and strength in one strain of chicks compared with 3 other broiler strains when fed extremely low concentrations of NPP. Most previous research concerning the NPP requirements of various broiler strains is quite dated, and, with the rapid genetic progress in the past 10 to 15 yr, data from modern broiler strains need to be reevaluated. A new strain of broiler, Ross 708 that has been developed for large bird or roaster production, has a slower initial growth rate than the Ross 308 strain that is used for multipurpose broiler production [21, 22]. Because of this difference in growth rate, it is important to determine if the strain difference is reflected in NPP requirement. The increased use of phytase in broiler diets suggests the importance of determining if phytase supplementation of the diets results in differences in bird performance and tibia ash due to bird strain. The few reported studies of bird strain responses on phytase supplementation have focused mainly on laying hen strains not broiler strains [23, 24]. We hypothesize that differences in bird growth will result in differences in dietary NPP requirements for weight gain, feed intake, and tibia ash in broiler chicks and that dietary phytase supplementation will affect the NPP requirements of Ross 308 and 708 chicks differently.

3 74 JAPR: Research Report Table 2. Performance and fat-free tibia ash of Ross 308 and Ross 708 chicks fed various concentrations of nonphytate P (NPP), Experiment 1 1 Strain Weight Feed Fat-free tibia ash and NPP gain intake Gain:feed Mortality (%) (g) (g) (g/kg) (g/bird) (%) (%) Ross Ross Pooled SEM ANOVA Source of variance Probability Strain NPP Strain NPP Data are means of 6 groups of 4 male Ross 308 and 708 chicks from 8- to 22-d; average initial chick weight on d8was 121 g for the Ross 308 chicks and 116 g for the Ross 708. MATERIALS AND METHODS General Chick Procedures Day-old male broiler chicks of 2 commercial strains, Ross 308 [22] and Ross 708 [21], were obtained from a local hatchery. Breeder flocks producing eggs for these experiments were of similar age, P nutrition, and management within each experiment. Breeder flock age in Experiments 1 to 3 for the Ross 308 and 708 birds Table 3. Single-slope broken line regression coefficients estimating calculated nonphytate P concentrations to maximize weight gain, feed intake and fat-free tibia ash of Ross 308 and 708 broiler chicks fed various concentrations of nonphytate P (NPP) with and without phytase (phy) supplementation, Experiments (Exp) 1 to 3 1 Regression coefficients Exp and Ross Weight gain Feed intake Tibia ash % strain Phy (%) r 2 SEM (%) r 2 SEM (%) r 2 SEM Calculated NPP (%) in Experiment 1: 0.13, 0.21, 0.29, 0.37, 0.45, 0.53; Experiment 2: 0.15, 0.21, 0.27, 0.33, 0.39, 0.45; Experiment 3: 0.15, 0.23, 0.31, 0.39, 0.47, Analyzed total P (%) in Experiment 1: 0.40, 0.48, 0.56, 0.64, 0.72, 0.80; Experiment 2: 0.45, 0.51, 0.57, 0.63, 0.69, 0.75; Experiment 3: 0.46, 0.54, 0.62, 0.70, 0.78, 0.86.

4 PERSIA AND SAYLOR: BROILER STRAIN AND PHOSPHORUS USE 75 Table 4. Performance and fat-free tibia ash of Ross 308 and Ross 708 chicks fed various concentrations of nonphytate P (NPP) with and without phytase, Experiment 2 1 Ross strain Weight Feed Fat-free tibia ash and phytase NPP gain intake Gain:feed Mortality (U/kg) (%) (g) (g) (g/kg) (g/bird) (%) (%) Pooled SEM ANOVA Source of variance Probability Strain Phytase NPP Strain phytase Strain NPP Phytase NPP Strain phytase NPP Data are means of 6 groups of 4 male Ross 308 and 708 chicks from 8 to 22 d; average initial chick weight on d8was 112 g for the Ross 308 chicks and 105 g for the Ross 708. were 35 and 36, 43 and 42, 38 and 36 wk, respectively. Chicks were housed in thermostatically controlled starter batteries [25] with raised wire floors contained in environmentally regulated rooms. Chicks were provided ad libitum access to feed and water. Continuous light was provided for the duration of all experiments. Chicks were fed a 23% CP corn-soybean meal pretest diet that met or exceeded all NRC [26] nutrient requirements during the first 7 d in Experiments 1 and 2 and the first 4 d in Experiment 3. Chicks were weighed, allotted to groups of 4 chicks so that mean body weight of all groups was similar, wing-banded, and randomly allotted to dietary treatments as described by Boomgaardt and Baker [27]. Experimental diets were mixed from a common basal diet (Table 1) with additions of limestone, dicalcium phosphate, and cellulose [28] to reach experimental Ca and NPP concentrations without changing energy or CP concentrations of the diets. Analyzed total P concentrations for basal diets in Experiments 1 to 3 were 0.40, 0.45, and 0.46%, respectively; and dicalcium phosphate was added to diets at an

5 76 JAPR: Research Report Table 5. Performance and fat-free tibia ash of Ross 308 and Ross 708 chicks fed various concentrations of nonphytate P (NPP) with and without phytase, Experiment 3 1 Ross strain Weight Feed Fat-free tibia ash and phytase NPP gain intake Gain:feed Mortality (U/kg) (%) (g) (g) (g/kg) (g/bird) (%) (%) Pooled SEM ANOVA Source of variance Probability Strain Phytase NPP Strain phytase Strain NPP Phytase NPP Strain phytase NPP Data are means of 6 groups of 4 male Ross 308 and 708 chicks from 5 to 23 d; average initial chick weight on d5was 72 g for the Ross 308 chicks and 71 g for the Ross 708. analyzed 18.5% total P [29]. Phytase utilized in Experiments 2 and 3 was supplied at the expense of cellulose; the dry product was premixed with a small amount of the basal diet before addition into mash diets [31]. Crude protein concentrations of the basal diets were determined utilizing duplicate 0.5-g diet samples and an Elementer vario max CN combustion analyzer [32]. In all 3 experiments, chick weight gain, feed intake, and feed efficiencies were calculated for the experimental period. At the end of each experiment, chicks were euthanized by CO 2 gas prior to collection of the right tibia for fat-free tibia ash determination [33]. Chicks were monitored daily for leg problems or mortality. Chicks that showed signs of severe leg problems were removed from the experiment, euthanized, and counted as mortalities. When mortality or leg problems occurred, birds were removed from the pen, and wing band, date, weight, and feeder weight were recorded to correct feed intake and feed efficiency for mortality losses. Statistical analysis was carried out utilizing the GLM function of SAS [34]. Statistical significance was

6 PERSIA AND SAYLOR: BROILER STRAIN AND PHOSPHORUS USE 77 assigned at P All animal procedures used in these experiments received approval from the University of Delaware Agricultural Animal Care and Use Committee. Experiment 1 The first chick experiment was designed to test the effects of broiler strain on 8- to 22-dold chicks fed various concentrations of NPP. The design was a 6 2 factorial arrangement with 6 concentrations of dietary NPP and 2 broiler strains. For this experiment, 288 commercial broiler chicks, 144 each of Ross 308 and Ross 708 males were assigned to 1 of 72 pens with 4 chicks per pen. Six replicate pens of each strain were fed 1 of 6 experimental diets containing 0.13, 0.21, 0.29, 0.37, 0.45, or 0.53% NPP. Chick weight gain, feed intake, and feed efficiency were calculated for the 14- d period, and fat-free tibia ash was determined on d 22. Experiment 2 The second chick experiment was designed to test the effects of broiler strain and phytase supplementation on 8- to 22-d-old chicks fed various concentrations of NPP. The design was a6 2 2 factorial arrangement, with 6 concentrations of dietary NPP, 2 broiler strains, and phytase supplementation. A total of 576 commercial broiler chicks, 288 each of Ross 308 and Ross 708 males, was assigned to 1 of 144 pens, 4 chicks per pen. Six replicate groups of each strain were fed 1 of 12 diets containing 0.15, 0.21, 0.27, 0.33, 0.39, or 0.45% NPP, with or without 600 U/kg of fungal phytase activity [37]. A narrower range of NPP concentrations was utilized in this experiment to more closely determine the NPP requirements of the broiler chicks supplemented with phytase. Chick weight gain, feed intake, and feed efficiency were calculated for the 14-d period, and fat-free tibia ash was determined on d 22. Experiment 3 The final chick experiment was designed to test the effects of broiler strain and phytase supplementation on 5- to 23-d-old chicks fed various concentrations of NPP. The design was a6 2 2 factorial arrangement with 6 concentrations of dietary NPP, 2 broiler strains, and phytase supplementation. As in Experiment 2, 576 commercial broiler chicks, 288 each of Ross 308 and Ross 708 males, were assigned to 144 pens, 4 chicks per pen. Six replicate groups of each strain were fed 1 of 12 diets containing 0.15, 0.23, 0.31, 0.39, 0.47, or 0.55% NPP, with or without 600 U/kg of fungal phytase activity. In Experiment 2, a narrow range of dietary NPP concentrations resulted in no plateau region for the Ross 308 chicks not given phytase supplementation, as they never stopped responding to increasing concentrations of NPP up to 0.45%. Therefore, a wider range of NPP concentrations was used to generate single-slope broken-line regression analysis equations for treatments with and without supplemental phytase in this experiment. Chick weight gain, feed intake, and feed efficiency were calculated for the 18-d period, and fatfree tibia ash was determined on d 23. RESULTS AND DISCUSSION In Experiment 1, NPP and broiler strain affected chick weight gain, feed intake, and tibia ash, although no interactions between the 2 were significant (Table 2). As expected, Ross 308 chicks grew significantly faster and consumed more feed than the slower developing Ross 708 chicks. Fat-free tibia ash presented on total grams per bird basis resulted in significant strain and NPP effects, but when expressed on a percentage basis the strain effect was no longer significant and was most likely due to the increased body weight of the Ross 308 chicks in comparison to the Ross 708 chicks. Increase of dietary NPP to 0.37% in both broiler strains resulted in increases in weight gain, feed intake, and fat-free tibia ash percentage after which no large increases in any response variable were noted with increasing dietary NPP. As expected, dietary concentrations of 0.45% NPP and above did not result in differences in weight gain or feed intake and were fed to calculate a single-slope broken-line regression estimate. Single-slope broken-line regression analysis resulted in NPP requirement estimates for weight gain, feed intake, and fat-free tibia ash percentage of 0.34, 0.33, and 0.35% for the Ross 308 chicks and 0.32, 0.33, and 0.36% for the Ross 708 chicks, respectively (Table 3).

7 78 JAPR: Research Report Although the differences in chick weight gain and feed intake were significant between Ross 308 and 708 chicks, they were not numerically large enough to substantially alter the NPP requirement of the 2 strains of chicks [13, 14, 15, 16, 17]. As reported in previous research, there was no difference in NPP requirement between broiler strains [18, 19]. It is interesting to note that the estimated NPP requirements for fat-free tibia ash percentage were higher than the requirements for weight gain and feed intake in both strains. Similar differences between NPP requirements for performance and tibia ash have been noted before [11]. Although tibia ash gives consistent results and is a straightforward measurement of chick P status, it has yet to be strongly correlated with processing losses in the field. Therefore, we believe that the NPP requirements for weight gain and feed intake are more applicable. Feed efficiency was significantly affected by dietary NPP with the 0.13% NPP concentration resulting in reduced feed efficiency in both strains of chicks. Chick mortality was significantly increased in both Ross 308 and 708 chicks fed extremely low NPP concentrations with a slightly greater increase in mortality of the Ross 708 chicks (P = 0.11). Dietary NPP, broiler strain, and phytase supplementation all significantly affected chick weight gain, feed intake, feed efficiency, and tibia ash in Experiment 2 (Table 4). Consistent with Experiment 1, the Ross 308 chicks gained more weight and consumed more feed from 8- to 22-d than the Ross 708 chicks. Unlike in Experiment 1, the Ross 308 chicks showed an increased feed efficiency in comparison to the Ross 708 chicks for the 8- to 22-d period. Similar to Experiment 1, both strain and dietary NPP concentration significantly affected fatfree tibia ash on a weight basis, but only NPP concentration affected fat-free tibia ash as a percentage of bone weight, again indicative of the body weight effect between the 2 strains. The addition of 600 U/kg of fungal phytase to the diets resulted in increases in weight gain, feed intake, feed efficiency, tibia ash, and a reduction in chick mortality in both strains of chicks, primarily in the chicks receiving the low NPP diets resulting in significant phytase NPP interactions. Unfortunately, with the reduced range of dietary NPP concentrations, the Ross 308 chicks fed the phytase-free diets exhibited increases in weight gain through the 0.45% NPP, resulting in a significant strain phytase NPP 3-way interaction. The significant 3-way interaction for feed efficiency was due to the exceedingly low performance of the Ross 708 chicks fed the 0.15 and 0.21% NPP without phytase supplementation compared with the nonsupplemented Ross 308 chicks or all phytase supplemented chicks. The high fatfree total tibia ash value for the Ross 308 chicks fed 0.45% NPP diets without phytase supplementation was responsible for the 3-way interaction noted. This effect can be explained, at least partially, by the increased weight gain of the Ross 308 chicks fed the 0.45% NPP diets without phytase supplementation compared with all other birds fed the 0.45% NPP diets. Chick mortality was not affected by strain, but chicks fed 0.15% NPP diets without phytase supplementation showed increased mortality, resulting in a significant phytase NPP interaction. Due to the increase in weight gain of Ross 308 chicks without phytase supplementation in Experiment 2, broken-line regression analysis was conducted only on the broiler chicks that received phytase supplementation. The results of Experiment 2 were in contrast to those of Experiment 1 in that Ross 308 chicks fed 0.45% NPP without phytase addition had weight gain greater than those chicks fed 0.37 or 0.39% NPP without phytase addition, suggesting a higher requirement for NPP in Experiment 2. A similar increase in weight gain response was noted in a previous report when feeding 0.4 and 0.5% dietary NPP [38]. Regression analysis yielded break-point requirement estimates of 0.35, 0.39, 0.36 and 0.27, 0.30, and 0.39 for chick weight gain, feed intake, and fat-free tibia ash percentage for phytase supplemented Ross 308 and Ross 708 chicks, respectively (Table 3). The low requirement estimates for the Ross 708 chicks for weight gain and feed intake are due to low weight gain and feed intake in comparison to the Ross 308 chicks. The Ross 708 chicks exhibited a general unthriftiness in Experiment 2 in relation to the growth of similar chicks in Experiment 1. Ross 708 chicks reaching the plateau region for gain or feed intake

8 PERSIA AND SAYLOR: BROILER STRAIN AND PHOSPHORUS USE 79 in Experiment 2 were 75 g lighter but consumed only 20 g less than Ross 708 chicks in Experiment 1. The unthriftiness experienced in Experiment 2 also increased the error estimate in comparison to other reported experiments. Although this unthriftiness and reduction in chick weight gain is unexplained, it is clear that it caused the reduced NPP requirement in the 708 chicks fed the phytase enzyme. Other authors have demonstrated differences in poultry NPP requirements with strains selected for either weight gain (broiler) or reproductive performance (layers), but this report is one of the first on differences in NPP requirements of various strains of broiler chicks [13, 14, 15, 16, 17]. In contrast to Experiment 1, the requirement estimates for feed intake are higher than those for weight gain. However, it is important to note the lower r 2 of the estimates for weight gain and feed intake compared with other requirement estimates. It is also important to avoid direct comparison of data from Experiments 1 and 2 to try to extrapolate a phytase effect. To this end, Experiment 3 was conducted with a wider range of NPP concentrations and multiple NPP concentrations above 0.45% NPP to encompass maximal responses of both strains of birds fed diets with and without phytase supplementation. In Experiment 3, Ross 308 chicks gained more weight, consumed more feed, and yielded increased total amounts of bone ash than Ross 708 chicks from d 5 to 23 (Table 5). Phytase supplementation resulted in increases in chick weight gain, feed intake, total tibia ash, and tibia ash percentage and reductions in chick mortality at lower concentrations of dietary CONCLUSIONS AND APPLICATIONS NPP resulting in significant phytase NPP interactions. These interactions were expected as phytase liberated P and increased P use in the chicks fed the low NPP diets [8]. The 3-way interaction among strain, phytase, and NPP for feed efficiency was due to the low gain:feed of the Ross 308 chicks fed the 0.15% NPP diet without phytase supplementation compared with all other chicks fed the 0.15% NPP diets. Single-slope broken-line regression analysis was completed for both strains of birds with and without phytase supplementation (Table 3). The NPP requirement estimates for chick weight gain, feed intake, and tibia ash percentage in Experiment 3 are higher than both requirement estimates in Experiments 1 and 2. This is most likely due to the earlier age of initiation of the dietary treatments in Experiment 3. As in Experiment 1, the NPP requirements for tibia ash percentage are higher than the NPP requirements for both weight gain and feed intake, regardless of phytase supplementation. The NPP requirements for chick weight gain estimated during these experiments are lower than those reported in the NRC [26] but similar to those reported by other authors [11, 39]. Phytase supplementation did reduce the NPP requirement estimate in both strains for weight gain, feed intake, and tibia ash percentage by an average of 8.5, 3.8, and 6.5%, respectively. This reduction in NPP requirement is similar in magnitude to the NPP release values generated by fungal phytase supplementation [8, 40]. Other authors have noted a greater difference in tibia ash response than performance response with fungal phytase supplementation [11]. 1. Nonphytate P requirements for 8- to 22-d old Ross 308 and 708 chicks demonstrating expected performance were 0.32 to 0.35, 0.33 to 0.39, and 0.35 to 0.39% for weight gain, feed intake, and tibia ash percentage, respectively. 2. Unthrifty Ross 708 chicks in Experiment 2 that exhibited below average performance had NPP requirements of 0.27, 0.30, and 0.39% for weight gain, feed intake and tibia ash percentage, respectively. 3. Moderate differences in weight gain between the 2 strains did not substantially alter NPP requirements of the chicks, but large differences in growth noted in Experiment 2 resulted in differences in NPP requirements between the 2 strains.

9 80 JAPR: Research Report 4. In younger, 5- to 23-d old, Ross 308 and 708 chicks, NPP requirements were elevated and ranged from 0.37 to 0.38 for weight gain, 0.39% for feed intake and 0.44 to 0.48% for tibia ash percentage. 5. Generally, NPP requirement for fat-free tibia ash percentage was higher than NPP requirements for weight gain or feed intake. 6. In Experiment 3, phytase supplementation reduced chick NPP requirements by 8.5, 3.8, and 6.5% for chick weight gain, feed intake, and tibia ash percentage, respectively. 1. Sharply, A. N., T. C. Daniel, J. T. Sims, and D. H. Pote Determining environmentally sound phosphorus levels. J. Soil Water Conserv. 51: Sims, J. T., R. R. Simard, and B. C. Joern Phosphorus loss in agricultural drainage: Historical perspective and current research. J. Environ. Qual. 27: Correll, D. L The role of phosphorus in the eutrophication of receiving waters: A review. J. Environ. Qual. 27: Kellogg, R. L., C. H. Lander, D. C. Moffitt, and N. Gollehon Manure nutrients relative to the capacity of cropland and pastureland to assimilate nutrients: Spatial and temporal trends for the United States. USDA, GSA Natl. Forms and Publ. Center, Fort Worth, TX. 5. Maguire, R. O., and J. T. Sims Soil testing to predict phosphorus leaching. J. Environ. Qual. 31: Nelson, T. S., T. R. Shieh, R. J. Wodzinski, and J. H. White Effect of supplemental phytase on the utilization of phytate phosphorus by chicks. J. Nutr. 101: Angel, R., N. M. Tamim, T. J. Applegate, A. S. Dhandu, and L. E. Ellestad Phytic acid chemistry: Influence on phytinphosphorus availability and phytase efficacy. J. Appl. Poult. Res. 11: Augspurger, N. R., D. M. Webel, X. G. Lei, and D. H. Baker Efficacy of an E. coli phytase expressed in yeast for releasing phytate-bound phosphorus in young chicks and pigs. J. Anim. Sci. 81: Angel, R Phosphorus in broilers: Maximizing retention. Pages in Proc. 46th Maryland Nutr. Conf., Timonium, MD. Univ. Maryland, College Park. 10. Angel, R., T. Applegate, and M. Christman Phosphorus requirements for broilers and effect of phytase, citric acid and 25-hydroxycholecalciferol on phosphorus availability for broilers and turkeys. Pages in Proc. 48th Maryland Nutr. Conf., Timonium, MD. Univ. Maryland, College Park. 11. Waldroup, P. W., J. H. Kersey, E. A. Saleh, C. A. Fritts, F. Yan, H. L. Stilborn, R. C. Crum, Jr., and V. Raboy Nonphytate phosphorus requirement and phosphorus excretion of broiler chicks fed diets composed of normal or high available phosphate corn with and without microbial phytase. Poult. Sci. 79: Yan, F., J. H. Kersey, C. A. Fritts, P. W. Waldroup, H. L. Stilborn, R. C. Crum, Jr., D. W. Rice, and V. Raboy Evaluation of normal yellow dent corn and high available phosphorus corn in combination with reduced dietary phosphorus and phytase supplementation for broilers grown to market weights in litter pens. Poult. Sci. 79: Gardiner, E. E Response of two breeds of chickens to graded levels of dietary phosphorus. Poult. Sci. 48: Andrew, T. L., B. L. Damron, and R. H. Harms Single Comb White Leghorn cockerels versus broiler chicks for use in phosphorus assays. Poult. Sci. 50: REFERENCES AND NOTES 15. Gardiner, E. E Inorganic phosphorus, organic phosphorus and inorganic calcium in blood plasma from two breeds of chickens fed various levels of dietary calcium and phosphorus. Can. J. Anim. Sci. 53: Edwards, H. M., Jr Phosphorus. 1. Effect of breed and strain on utilization of suboptimal levels of phosphorus in the ration. Poult. Sci. 62: Elliot, M. A., and H. M. Edwards, Jr Effect of genetic strain, calcium and feed withdrawal on growth, tibial dyschondroplasia, plasma 1,25-dihydroxycholecalciferol and plasma 25- hydroxycholecalciferol in sixteen-day-old chickens. Poult. Sci. 73: Lillie, R. J., P. F. Twining, and C. A. Denton Calcium and phosphorus requirements of broilers as influenced by energy, sex, and strain. Poult. Sci. 43: Shafey, T. M., M. W. McDonald, and R. A. E. Pym Effects of dietary calcium, available phosphorus and vitamin D on growth rate, food utilization, plasma, and bone constituents and calcium and phosphorus retention of commercial broiler strains. Br. Poult. Sci. 31: Orban, J. I., and D. A. Roland, Sr Response of four broiler strains to dietary phosphorus above and below the requirement when brooded at two temperatures. Poult. Sci. 69: Ross Ross 708 North American Broiler Performance Objectives. Aviagen North America, Huntsville, AL. 22. Ross Ross 308 North American Broiler Performance Objectives. Aviagen North America, Huntsville, AL. 23. Scott, T. A., R. Kampen, and F. G. Silversides The effect of adding exogenous phytase to nutrient-reduced corn- and wheat-based diets on performance and egg quality of two strains of laying hens. Can. J. Anim. Sci. 81: Keshavarz, K The effect of different levels of nonphytate phosphorus with and without phytase on the performance of four strains of laying hens. Poult. Sci. 82: Petersime Incubator Co., Gettysburg, OH. 26. National Research Council Nutrient Requirements of Poultry. 9th rev. ed. Natl. Acad. Press, Washington, DC. 27. Boomgaardt, J., and D. H. Baker Tryptophan requirement of growing chicks as affected by dietary protein level. J. Anim. Sci. 33: Solka-Floc, International Fiber Corp., North Tonawanda, NY. 29. Digestion of basal diets was completed in duplicate by burning in a 550 C oven for at least 8 h before boiling in 10 ml of concentrated nitric acid and then 20 ml of 30% hydrogen peroxide before being solubilized in 10% hydrochloric acid [30]. Dicalcium phosphate and limestone were analyzed in triplicate by digestion in 10 ml of concentrated nitric acid before being solubilized in 10% hydrochloric acid. Phosphorus and Ca detection were by inductively coupled plasma atomic emission spectrometry (ICP-AES).

10 PERSIA AND SAYLOR: BROILER STRAIN AND PHOSPHORUS USE Wedekind, K. J., and D. H. Baker Zinc bioavailability in feed-grade sources of zinc. J. Anim. Sci. 68: Ronozyme, DSM Nutritional Products, Inc., Parsippany, NJ. Phytase was added based on analyzed product batch concentration of 3,060 U/g of product. 32. Elementor, Mt. Laurel, NJ. 33. Association of Official Analytical Chemists Official Methods of Analysis, 13th ed. Washington, DC. 34. SAS User s Guide Version 8 ed. SAS Inst. Inc., Cary, NC. In Experiment 1, treatments were analyzed using a 6 2 factorial arrangement of treatments in a completely randomized design. In Experiments 2 and 3, treatments were analyzed using a factorial arrangement of treatments in a randomized complete block design. Chick battery was assigned as the blocking factor due to placement of the 6 batteries in various locations. Data are reported as means of 6 replicate groups of 4 chicks for each treatment with a pooled SEM. Mortality data were arc sin transformed prior to statistical analysis with means and pooled SEM reported from untransformed data [35]. In all 3 experiments, singleslope broken-line regression equations were calculated for each strain of bird fed various levels of NPP with and without phytase supplementation to determine NPP requirement estimates [36]. The NPP requirement estimates, r 2 values and standard error of the means are reported in Table 3. Broken-line regression estimates were not carried out in Experiment 2 on nonphytase supplemented chicks due to the narrow response range and failure of the Ross 308 chicks to reach a plateau in weight gain, feed intake and tibia ash. 35. Freund, R. J., and W. J. Wilson Inferences for two or more means. Pages in Statistical Methods. Academic Press, Inc., San Diego, CA. 36. Robbins, K. R., H. W. Norton, and D. H. Baker Estimation of nutrient requirements from growth data. J. Nutr. 109: A unit is defined as the amount of enzyme required to liberate 1 mol of inorganic P from 1.5 mmol of sodium phytate at 37 C and ph Persia, M. E., C. M. Parsons, and K. W. Koelkebeck Interrelationship between environmental temperature and dietary nonphytate phosphorus in chicks. Poult. Sci. 82: Angel, R., T. J. Applegate, M. Christman, and A. D. Mitchell Effect of dietary non-phytate phosphorus (npp) level on broiler performance and bone measurements in the starter and grower phase. Poult. Sci. 79(Suppl. 1):22. (Abstr.) 40. Angel, R., W. W. Saylor, A. S. Dhandu, W. Powers, and T. J. Applegate Effects of dietary phosphorus, phytase, and 25-hydroxycholecalciferol on performance of broiler chickens grown in floor pens. Poult. Sci. 84: