Determination of Nutrient Mass Balance in Turkeys

Determination of Nutrient Mass Balance in Turkeys

Determination of Nutrient Mass Balance in Turkeys T. Applegate,*1 S. Adedokun,* W. Powers,† and R. Angel‡ *Department of Animal Sciences, Purdue Unive...

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Determination of Nutrient Mass Balance in Turkeys T. Applegate,*1 S. Adedokun,* W. Powers,† and R. Angel‡ *Department of Animal Sciences, Purdue University, West Lafayette, IN 47907-2054; †Department of Animal Science, Michigan State University, East Lansing 48824-1225; and ‡Department of Animal and Avian Sciences, University of Maryland, College Park 20742-2311 percentage of phosphorus consumed was greater at 12, 15, and 18 wk for birds fed the LP diets (67.0, 63.8, and 53.8%) than for birds fed the IND diets (47.3, 44.0, and 32.8%). The difference between the mass of phosphorus excreted, as calculated from litter, compared with feed intake minus carcass retention was less than 5% at 18 wk. The nitrogen retained averaged 90.7, 136.7, and 184.2 g/bird, whereas nitrogen excreted averaged 377.6, 620.7, and 921.8 g/bird at 12, 15, and 18 wk of age, respectively. Additionally, with an 18-wk average litter DM of 78.0%, the unaccounted for nitrogen at 18 wk was 427 and 405 g/bird for birds fed the IND and LP diets, respectively (40 and 37% of excreted nitrogen).

Key words: mass balance, nitrogen, nutrient excretion, phosphorus, turkey 2008 Poultry Science 87:2477–2485 doi:10.3382/ps.2008-00056

INTRODUCTION Nitrogen and phosphorus from poultry litter have been reported to have potential negative effects on air, soil, and water quality (Loehr, 1972; O’Connor et al., 1988; Smith et al., 2001). Some of the potential problems associated with animal emissions are eutrophic conditions that result from phosphorus in excreta and runoff (Smith et al., 2004; Angel et al., 2005), as well as acidification of the environment resulting from ammonia, sulfur compounds, nitrogen oxides, and volatile organic compounds (Groot Koerkamp, 1994). Measures taken to reduce nutrient excretion include dietary modifications (de Lange et al., 1999; Smith et al., 2004; Wu-Haan et al., 2007), which include the mass reduction in dietary nutrients fed over the lifetime of the animal (Elwinger and Svensson, 1996); the use of phytase, an enzyme that works by releasing phosphate groups that are tightly bound to the phytate molecule, thereby making phosphorus available for absorption (Nelson et al., 1968); and a reduction in dietary CP concentration (Ferguson et al., 1998). ©2008 Poultry Science Association Inc. Received January 31, 2008. Accepted August 7, 2008. 1 Corresponding author: [email protected]

Overfeeding of dietary phosphorus is common commercially, with excesses of as much as 30% over published requirements commonly observed. Part of this overfeeding is due to the lack of an up-to-date publication on poultry phosphorus requirements. The most recent nutrient recommendations for poultry were published by NRC in 1994, and the recommendations for turkeys are based on data published from 1954 to 1986, respectively. Genetic progress has greatly changed the performance of commercial turkeys since then, so industry nutritionists have limited resources to which to refer for the requirements of their modern genetic strains. Even though the NRC (1994) recommendations are based on turkey experiments conducted from 1954 to 1986, they appear to be consistent with the current needs of the turkey (Roberson and Fulton, 2000; Roberson et al., 2000; Thompson et al., 2002). Although these studies demonstrate that the NRC (1994) feeding recommendations of phosphorus are still adequate, no data are available quantifying the impact of phosphorus feeding programs in turkeys on the mass of nutrients excreted. This study therefore had several objectives. The first was to confirm the lack of performance differences when turkey toms were fed a typical corn-soybean meal-based industry diet (IND) and a diet containing a reduced concentration of inorganic phosphorus supplemented

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ABSTRACT Retention and excretion of phosphorus and nitrogen were determined for turkeys fed 2 diets at 3 ages, via mass balance based on the nutrient content of consumed feed, carcasses, and litter. The 2 diets consisted of an industry diet (IND) and a low phosphorus + 600 U of phytase/kg (LP) diet. A subsample of birds was weighed and killed at 12, 15, and 18 wk of age for nutrient retention (via whole carcasses) and excretion (via litter). Diet did not affect BW or feed intake from 12 to 18 wk of age. The mass of phosphorus excreted from 0 to 12, 0 to 15, and 0 to 18 wk of age was 37, 46, and 40% greater for birds fed the IND diets compared with birds fed the LP diets. Phosphorus retained as the

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MATERIALS AND METHODS Two feeding regimens were used in this study: a typical corn-soybean meal-based IND diet and an LP diet containing a relatively low concentration of nonphytate phosphorus (nPP) supplemented with 600 units of phytase/kg of diet (Ronozyme, DSM, Ft. Lee, NJ). The CP, nPP, and phytase contents of the experimental diets are reported in Table 1. The formulated CP concentration of both diets was similar at all ages, whereas the nPP was decreased, relative to the IND, in the LP diets at all ages. All diets were initially mixed as a basal ration containing corn, soybean meal, and a vitamin-trace mineral premix to minimize nutrient content variation caused by mixing. The final diets were subsequently mixed with 98% of the basal ration and varying amounts of limestone, monocalcium phosphate, and phytase to meet the desired concentrations of calcium and nPP. All diets were fed in mash form.

Turkey Trial All animal care and use was approved by the Purdue University Animal Care and Use Committee. Toms were reared in 3.72-m2 floor pens containing 10 cm of wood shavings on top of a concrete floor. A total of 192 male turkey poults were individually weighed and placed into 24 pens with 8 poults per pen such that the mean pen BW between pens was not statistically different. Each diet was fed to 12 replicate pens. Turkey poults were provided with starter feed and water ad libitum for 3 wk, after which poults in each pen were weighed. Five turkeys with the weight closest to the mean of all birds in the pen were retained, whereas the rest were removed from the trial. Feed (and nutrient) intake during this initial period was used for mass balance determinations, whereas the BW of the additional 3 birds (less mortality) was not included in the mass of nutrients retained within the body. Diets were changed at the end of every 3-wk period. At the end of every

3-wk period, turkey BW and feed consumption were determined. At wk 12, 4 pens for each of the diets were randomly selected, and birds were killed, labeled, and frozen for determination of carcass nutrient retention. This same procedure was repeated at wk 15 and 18.

Litter and Turkey Carcass Before the beginning of the study, wood shavings in each of the pens were weighed. On wk 12, 15, and 18, when birds from 4 pens per diet were killed, all the litter from each pen was collected, weighed, thoroughly mixed (in a 0.254-m3 cement mixer; Crown Construction Equipment; Winnipeg, Manitoba, Canada), and subsampled. The DM content of litter from each pen was determined after drying for 72 h in a forced-air oven at 55°C in duplicate. Dried litter was then ground to pass through a 1-mm screen. Litter mineral content was determined by inductively coupled plasma spectroscopy (University of Arkansas, Central Analytical Laboratory, Fayetteville; AOAC, 1999) after wet digestion. Nitrogen contents of diets, carcasses, and litter were determined by Kjeldahl digestion and distillation (AOAC, 2000). Phosphorus contents of diets, carcasses, and litter were ashed in a muffle furnace at 550°C for 4 h and then digested, and total phosphorus was determined colorimetrically (AOAC, 1980). Feed phytase content was determined colorimetrically (Engelen et al., 1994). One unit of phytase was defined as the amount of phytase needed to liberate 1 μmol of inorganic phosphorus/min from 5.1 mmol/L of sodium phytate at pH 5.5 and 37°C. The litter weight and nutrient content at the beginning of the trial were subtracted from the pen litter content at the end of each phase to determine actual nutrient excretion values. By pen, frozen turkey carcasses (including feathers) were ground twice through a large meat grinder (Model 810 Gear Head, Autio, Astoria, OR). The ground carcasses were thoroughly mixed, and 25% of the total was subsampled and frozen for further preparation. Dry matter was determined in a portion of the sample by oven-drying duplicate samples (25 g) at 60°C for 72 h. The rest of the sample was partially dried (to approximately 70% DM) in a freeze-drier, frozen, and then ground in a freeze-grinder (Model 6850 Freezer/Mill, SPEX CertiPrep Inc., Metuchen, NJ) with liquid nitrogen. After grinding, the sample was lyophilized and stored frozen until analyzed. Samples were analyzed for mineral content by inductively coupled plasma spectroscopy after acid digestion (AOAC, 1999).

Calculation and Statistical Analysis Nutrient retention and excretion were estimated on both a weight and a percentage basis. True nutrient retention was determined as the mass of nutrient in the carcass of the bird, whereas apparent nutrient retention was determined as the difference between the mass of nutrient in the feed consumed and the mass of nutrient

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with exogenous phytase (LP). The second was to determine the nutrient (phosphorus, nitrogen, sulfur, sodium, potassium, and calcium) retention and excretion by turkey toms fed the IND and LP diets. Because nutrient excretion was determined by 2 distinct methods, differences in apparent nutrient retention (nutrient in feed − nutrient in litter) and true nutrient retention (nutrient in ground carcass) were used to calculate apparent nutrient volatilization. Recently, the American Society for Agricultural and Biological Engineers (ASABE) has updated its Manure Characteristics and Composition standard (D384.2; ASABE, 2005) and has used diet composition as a predictor of nutrient excretion. Because diets differing in phosphorus concentration were fed, data from this study were used to compare the accuracy of the standard D384.2 (ASABE, 2005) equations for turkeys to predict nutrient excretion.

39.55 51.13 3.05 0.41 0.23 0.06 2.01 1.59 0.05 0.35 1.57 0.02 28.5 2,850 1.20 0.29 0.52 0.81 4.50 (28.1) 1.45 0.86 0.29 0.17 1.46 752

28.5 2,850 1.40 0.29 0.70 0.99 4.26 (26.6) 1.54 0.98 0.27 0.12 1.43 98

Low P

39.55 51.13 3.05 0.41 0.23 0.06 2.12 2.45 0.05 0.35 0.62 —

IND

4.02 (25.1) 1.37 0.86 0.24 0.13 1.29 119

26.5 2,950 1.30 0.27 0.65 0.92

43.23 46.32 4.15 0.41 0.13 0.11 1.97 2.31 0.05 0.35 0.99 —

IND

4.10 (25.6) 1.26 0.65 0.23 0.15 1.26 696

26.5 2,950 1.00 0.27 0.42 0.69

43.23 46.32 4.15 0.41 0.13 0.11 1.71 1.21 0.05 0.35 2.32 0.02

Low P

3 to 6 wk

3.64 (22.8) 1.39 0.81 0.23 0.17 1.18 96

24.5 3,101 1.20 0.27 0.6 0.87

48.07 41.29 5.41 0.41 0.14 0.10 1.80 2.14 0.01 0.35 0.29 —

IND

3.79 (23.7) 0.97 0.57 0.22 0.15 1.17 771

24.5 3,101 0.84 0.27 0.34 0.61

48.07 41.29 5.41 0.41 0.14 0.10 1.45 0.90 0.01 0.35 1.85 0.02

Low P

6 to 9 wk

3.75 (23.5) 1.17 0.83 0.22 0.13 1.17 108

24.5 3,101 1.10 0.27 0.6 0.87

48.04 41.29 5.41 0.41 0.14 0.10 1.70 2.12 0.04 0.35 0.40 —

IND

IND 61.13 28.93 5.46 0.40 0.12 0.11 1.38 1.55 0.05 0.35 0.54 — 19.5 3,240 0.90 0.24 0.45 0.69 2.93 (18.3) 1.07 0.70 0.19 0.14 1.07 67

48.04 41.29 5.41 0.41 0.14 0.10 1.50 0.92 0.04 0.35 1.90 0.02 24.5 3,101 0.76 0.27 0.34 0.61 3.61 (23.5) 0.92 0.59 0.21 0.12 1.17 722

2.86 (17.9) 0.76 0.45 0.18 0.12 0.88 630

19.5 3,240 0.64 0.24 0.24 0.48

61.13 28.93 5.46 0.40 0.12 0.11 1.18 0.55 0.05 0.35 1.72 0.02

Low P

12 to 15 wk

Low P

9 to 12 wk

2

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2.39 (14.9) 0.90 0.60 0.16 0.11 0.90 73

17.25 3,300 0.80 0.22 0.40 0.62

67.13 23.26 5.51 0.41 0.08 0.12 1.24 1.37 0.05 0.35 0.65 —

IND

2.48 (15.5) 0.64 0.38 0.15 0.14 0.76 679

17.25 3,300 0.56 0.22 0.20 0.42

67.13 23.26 5.51 0.41 0.08 0.12 1.07 0.42 0.05 0.35 1.75 0.02

Low P

15 to 18 wk

IND = industry-type diet; Low P = low-phosphorus diet. Elanco Animal Health (Greenfield, IN). 3 Supplied per kilogram of diet: vitamin A, 13,233 IU; vitamin D3, 6,636 IU; vitamin E, 44.1 IU; vitamin K, 4.5 mg; thiamine, 2.21 mg; riboflavin, 6.6 mg; pantothenic acid, 24.3 mg; niacin, 88.2 mg; pyridoxine, 3.31 mg; folic acid, 1.10 mg; biotin, 0.33 mg; vitamin B12, 24.8 µg; choline, 669.8 mg; iron from ferrous sulfate, 50.1 mg; copper from copper sulfate, 7.7 mg; manganese from manganese oxide, 125.1 mg; zinc from zinc oxide, 125.1 mg; iodine from ethylene diamine dihydroidide, 2.10 mg; selenium from sodium selenite, 0.30 mg. 4 Contains, in percentage of the basal corn, soybean meal (48%), soybean oil, salt, dl-methionine, lysine, limestone, monocalcium phosphate, Coban 60, and vitamin-mineral premix: 39.6, 51.1, 3.05, 0.41, 0.23, 0.06, 1.78, 1.40, 0.05, 0.34 (0 to 3 wk); 43.2, 46.3, 4.15, 0.41, 0.13, 0.11, 1.20, 1.06, 0.05, 0.34 (3 to 6 wk); 48.1, 41.3, 5.41, 0.41, 0.14, 0.10, 1.00, 0.72, 0.01, 0.34 (6 to 9 wk); 48.1, 41.3, 5.41, 0.41, 0.14, 0.10, 1.00, 0.72, 0.01, 0.34 (9 to 12 wk); 61.1, 28.9, 5.46, 0.41, 0.12, 0.11, 0.59, 0.38, 0.05, 0.34 (12 to 15 wk); and 67.1, 23.1, 5.48, 0.41, 0.08, 0.12, 0.55, 0.21, 0.05, 0.34 (15 to 18 wk). 5 DSM Inc. (Ft. Lee, NJ).

1

  Calcium (%)   Phosphorus (%)   Sulfur (%)   Sodium (%)   Potassium (%)   Phytase (units/kg of diet)

Ingredient (%)   Corn   Soybean meal (48% CP)   Soybean oil   Salt   dl-Methionine   l-Lysine∙HCl   Limestone   Monocalcium phosphate   Coban 602   Vitamin-mineral premix3,4   Celite   Ronozyme phytase5 Calculated nutrient value   CP (%)   MEn (kcal/kg)   Calcium (%)   Phytate phosphorus (%)   Nonphytate phosphorus (%)   Total phosphorus (%) Analyzed value   Nitrogen (%) (CP, %)

Item

0 to 3 wk

Table 1. Composition of the experimental diets1 (as-is basis)

NUTRIENT MASS BALANCE IN TURKEYS AT THREE AGES

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Table 2. References used for average apparent nitrogen and phosphorus excretion for derivation of the American Society for Agricultural and Biological Engineers Manure Production and Characteristics standard (D384.2; ASABE, 2005) Apparent excretion1 Reference

Nitrogen (%) 2

Slaugh et al. (1989) Leeson and Atteh (1995) Mian and Garlich (1995) Piquer et al. (1995) Qian et al. (1996) Yi et al. (1996) Zyla et al. (1996)

53.1 45.2 66.1 57.0 ND ND ND ND ND ND 37.4 41.5 57.3

RESULTS

1 Where 2 values are presented, these are the results from 2 separate experiments. 2 ND = not determined.

in the litter. Additionally, true nutrient excretion was determined as the difference between the mass of nutrient fed and the mass of nutrient in the carcass, whereas apparent nutrient excretion was defined as the mass of nutrient in the litter. Unaccounted for nutrient content was subsequently calculated as the difference between true and apparent nutrient excretion (i.e., this difference is likely the nutrient that was apparently volatilized). Data were analyzed as a completely randomized design by ANOVA to determine differences attributable to dietary regimen within each age (SAS Institute, Cary, NC). A pen of birds was the experimental unit. Additionally, the formulated dietary nitrogen and phosphorus concentrations were used with actual feed consumption data for each pen to predict nitrogen and phosphorus excretion according to the prediction equations of standard D384.2 (ASABE, 2005). The D384.2 publication (ASABE, 2005) uses an average nutrient excretion value for turkeys based on published literature from 1985 to 2002 (Applegate et al., 2003). The publications used only values from turkeys fed cornsoybean meal-based diets and diets that were closer to the age-specific nutrient requirements of the bird. The references and apparent nitrogen and phosphorus excretion values are presented in Table 2. The aver-

The effects of treatments on BW, feed intake, and feed-to-gain ratio (F:G) are reported in Table 3. Dietary treatment did not have a significant effect on the average BW of toms except at wk 15, when toms on the IND diet were heavier than toms fed the LP diet. Toms fed the IND diet consumed more feed than birds fed the LP diet (wk 12 and 15). On wk 18, however, feed intake of toms fed the LP diet was greater than feed intake of those fed the IND diet. There was no difference in F:G at any of the ages evaluated in this study. The mass of excreta (ending litter weight − starting litter weight) was greater for birds fed the LP diet at 12 wk and greater for birds fed the IND diet at wk 15, but was not affected by diet at 18 wk (Table 4). Nitrogen, phosphorus, sulfur, sodium, potassium, and calcium retention values are reported in Table 5. Dietary treatments affected true nitrogen retention at wk 15, with toms fed the IND diet retaining more nitrogen than toms fed the LP diet (140 vs. 134 g). When expressed as a percentage, birds fed the LP diet (wk 15 = 18.3%; wk 18 = 17.0%) had greater true nitrogen retention compared with toms fed the IND diet (wk 15 = 17.8%; wk 18 = 13.3%). For apparent nitrogen retention, feeding the IND diet resulted in greater apparent nitrogen (mass) retention (wk 12), whereas apparent nitrogen retention for toms fed the LP diet was greater (wk 15) than for toms fed the IND diet. Phosphorus retention (true and apparent, mass) was greater in birds fed the LP diet on wk 18, but not on

Table 3. Mean BW, feed intake, and feed-to-gain ratio of turkey toms fed diets with (low-phosphorus diet) or without (industry diet) phytase1 BW (kg/bird) Item Industry Low P2 SEM a,b

12 wk

15 wk

8.86 8.84 0.255

a

12.72 12.08b 0.437

Feed intake (kg/bird) 18 wk 15.99 16.08 0.394

Feed:gain

12 wk

15 wk

18 wk

12 wk

15 wk

18 wk

a

a

b

1.58 1.57 0.301

2.01 2.01 0.365

2.50 2.48 0.091

14.44 13.28b 0.666

24.76 23.53b 0.739

36.67 37.31a 0.519

Means within column with no common superscripts differ (P < 0.05). Means represent 12, 8, and 4 pens per diet (5 birds per pen) at 12, 15, and 18 wk of age, respectively. 2 Low-phosphorus diet plus supplemental phytase. 1

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ND ND 43.0 24.6 52.2 38.4 43.0 49.6 45.8 57.3 47.8 51.9 ND

Phosphorus (%)

age apparent nitrogen and phosphorus excretion values were 41.2 ± 8.3% and 52.0 ± 7.2%, respectively. The equations in standard D384.2 (ASABE, 2005) for apparent excretion were then used to calculate apparent excretion based on feed nutrient content and intake from the current study. Thus, the comparisons were between the standard D384.2 (ASABE, 2005) equation estimations of nutrient excretion and the measured apparent excretion values. Comparisons were then made between predicted nitrogen and phosphorus excretion (via standard D384.2; ASABE, 2005) and measured apparent nutrient excretion by ANOVA within age and dietary regimen. All statements of significance were P < 0.05 unless indicated otherwise.

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NUTRIENT MASS BALANCE IN TURKEYS AT THREE AGES Table 4. Apparent excreta weight (ending litter dry weight − starting litter dry weight) and litter DM concentration from turkey toms at 3 different ages after being fed diets with (low-phosphorus diet) or without (industry diet) phytase1 Excreta (kg/bird) Item Week 0 to 12 Week 0 to 15 Week 0 to 18

Industry b

4.70 8.75a 12.00

Litter DM (%) 2

SEM

Industry

Low P2

SEM

a

0.276 0.310 1.020

77.45 81.73a 77.85

77.23 68.58b 78.23

2.549 3.257 5.364

Low P

5.50 8.35b 12.35

a,b

Means within row with no common superscripts differ (P < 0.05). Means represent 4 pens per diet (5 birds per pen). 2 Low-phosphorus diet plus supplemental phytase. 1

iron, manganese, magnesium, and zinc at wk 18 (IND diet) was 5.8 (±0.3), 0.49 (±0.03), 54.4 (±3.1), 28.5 (±1.6), 60.6 (±3.2), and 5.7 (±0.3) g/bird, respectively (mean ± SEM; data not shown). The amounts of nitrogen, phosphorus, and sulfur that were unaccounted for (grams per bird and percentage) is presented in Table 7. The unaccounted for phosphorus, which was calculated as the difference between true phosphorus and apparent phosphorus excretion, was negative, indicating that phosphorus was not volatilized. Rather, the negative value was due to residual error in each mass balance measurement or the presence of phosphorus from another source, such as drinking water (water mineral content was not measured, however). The unaccounted for nitrogen was greater for birds fed the IND diet (wk 12), and by wk 15 the unaccounted for nitrogen (in grams per bird) was greater for toms fed the LP diet. The amount of sulfur that could not be accounted for was greater for toms fed the IND diet (wk 12 and 15). Notably, when averaged across ages and diet, the ASABE equation estimates were not different from measured values (P ≥ 0.17). The values were within 8.1 and 17.2% of each other (for apparent nitrogen and phosphorus excretion, respectively). When analyzed within a particular age or diet; however, differences between the estimates and measured values were evident (Table 8). In particular, values for toms fed the IND diets were substantially different from those of standard D384.2 (ASABE, 2005), which underestimated excretion by 13.4 to 25.5%. When birds were fed more closely to requirements with supplemental phytase, the predicted values were not different from those measured at 0 to 12 or 0 to 15 wk, but apparent phosphorus excretion was underestimated by 18.5 g/bird (a 14.7% difference).

DISCUSSION The addition of phytase to the diet and feeding closer to the dietary phosphorus requirement resulted in no differences in final BW or F:G between treatments at 18 wk. Excreta weight and litter DM percentage at wk 18 were not affected by dietary treatments. The DM percentage of the litter in this study was within the 60 to 80% required for maximal ammonia emission, as

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wk 12 and 15 for true phosphorus retention (Table 5). Percentage of phosphorus retention was greater in toms fed the LP diet than in toms fed the IND diet. True sulfur retention (mass) at wk 18 was greater in toms fed the IND diet compared with those fed the LP diet. Apparent sulfur retention (mass) was greater at 12 and 15 wk from toms fed the IND diet compared with birds fed the LP diet, but not at 18 wk. Sulfur retention (%) was greater in birds fed the LP diet (true sulfur retention, wk 12 and 15; apparent sulfur retention, wk 15 and 18) than in birds fed the IND diet. Diet did not have any effect on sodium or potassium retention. The mass of calcium retained by toms fed either the IND or LP diet was similar. However, because dietary calcium:phosphorus ratios were maintained, the LP diet resulted in a greater percentage of calcium retained. Nitrogen, phosphorus, sulfur, sodium, potassium, and calcium excretions are reported in Table 6. The relative amount of nitrogen excreted increased with age. When nitrogen excretion was estimated by the difference between nutrient intake and the nutrient in carcass (true excretion), nitrogen excretion was greater in toms fed the IND diet (wk 15), whereas there was no difference at either 12 or 18 wk. Diet affected nitrogen excretion (apparent nitrogen excretion, as determined from litter) with the apparent excretion from LP birds being greater at 12 wk but less than that of the IND-fed birds at 15 wk. Although the trend in nitrogen excretion was similar, the estimate of nitrogen excretion from the litter was approximately 50% of that determined from the carcass method. True phosphorus excretion, both in percentage and in grams per bird, was greater for the IND diet, and there was a relative increase in phosphorus excretion with age. True sulfur excretion (in grams per bird) was greater for toms on the IND diet (wk 12 and 15) and at wk 15 and 18 (in percentage, apparent method). Diet did not affect sodium and potassium excretion (grams or percentage) at any age evaluated in this study. Mineral excretion per turkey increased with age, with nitrogen, phosphorus, sulfur, sodium, potassium, and calcium true excretion at wk 18 (IND diet) being 939, 201, 38, 84, 306, and 241 g/ bird, respectively. The corresponding values for apparent excretion were 482, 209, 39, 170, 334, and 253 g/ bird. Apparent mineral excretion of aluminun, copper,

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Table 5. Nitrogen, phosphorus, sulfur, sodium, and potassium retention of turkey toms fed diets with (low-phosphorus diet) or without (industry diet) phytase1 True retention2 Item Nitrogen   g/bird  % Phosphorus   g/bird  %

 % Sodium   g/bird  % Potassium   g/bird  % Calcium   g/bird

 %

Industry

Low P4

SEM

Industry

Low P4

SEM

0 0 0 0 0 0

to to to to to to

12 15 18 12 15 18

91.4 139.8a 185.7 18.8 17.8b 13.3b

90.0 133.7b 182.7 19.3 18.3a 17.0a

4.76 4.06 5.54 0.99 0.38 2.49

265.3a 389.5b 576.0 56.0a 49.8b 53.3

214.0b 417.4a 587.4 46.8b 57.0a 53.8

16.12 22.98 52.96 2.83 1.99 3.66

0 0 0 0 0 0

to to to to to to

12 15 18 12 15 18

58.3 91.5 97.3b 47.3b 44.0b 32.8b

59.1 90.2 111.6a 67.0a 63.8a 53.8a

3.03 8.85 8.34 2.96 4.37 2.59

51.2a 74.2a 101.9a 41.8b 36.0b 34.3b

43.2b 69.6b 87.3b 48.5a 49.5a 42.3a

3.87 2.76 9.31 3.59 0.79 2.69

0 0 0 0 0 0

to to to to to to

12 15 18 12 15 18

20.1 27.9 30.6a 70.3b 58.0b 45.5

20.3 28.0 29.3b 75.7a 64.8a 45.5

1.02 0.61 0.84 2.09 1.17 2.52

15.1a 22.2a 30.0 52.5a 46.3b 44.3b

13.1b 21.2b 30.5 49.0b 49.0a 47.0a

0.72 0.98 2.48 2.64 2.13 2.54

0 0 0 0 0 0

to to to to to to

12 15 18 12 15 18

7.4 10.3 12.2 43.8 33.0 27.0

7.2 10.1 12.5 43.3 35.8 26.8

0.21 0.34 0.38 1.33 0.73 1.095

7.0 10.3 11.8 41.3 32.5 26.0

5.7 8.1 12.7 34.8 28.8 26.8

0.40 0.75 1.90 3.31 2.69 3.53

0 0 0 0 0 0

to to to to to to

12 15 18 12 15 18

27.3 38.8 45.7 18.3 15.8 13.3

27.6 36.8 46.3 19.0 16.0 13.8

1.25 1.21 1.41 0.73 0.34 0.38

7.7 10.1 17.6 5.8 3.8 5.0

−5.2 7.5 20.9 −3.8 3.0 5.8

6.99 6.95 16.54 4.77 3.07 4.53

0 to 12 0 to 15 0 to 18

93.9 145.6 143.1

84.5 140.5 164.8

68.7 104.9 130.7

53.9 106.1 144.5

7.6 11.3 11.9

0 to 12 0 to 15 0 to 18

58.5 53.8 37.8b

69.0 71.5 57.0a

8.7 18.3 18.9 5.9 7.3 5.5

43.8 39.0 34.3b

49.0 54.5 50.3a

5.9 5.1 2.7

a,b

Means within row with no common superscripts differ (P < 0.05). Means represent 4 pens per diet (5 birds per pen). 2 Nutrients in carcass. 3 Difference between nutrients consumed in feed and nutrients in litter. 4 Low-phosphorus diet plus supplemental phytase. 1

reported by Groot Koerkamp (1994). The reduced DM content of the litter on the LP diet at wk 15 may have resulted in greater ammonia emission compared with the other ages. Notably, unaccounted for nitrogen was still 27 to 40% of excreted nitrogen. To quantify the amount of nitrogen and sulfur volatilized during the course of the experiment, the difference between the 2 methods of estimating nutrient retention and excretion was used. The true retention values were the quantity of a specific nutrient found in ground carcass, whereas true excretion was the difference between the nutrient consumed in the diets and nutrient retained in the carcass. Apparent retention values were determined as the difference between the

nutrient consumed in feed and the nutrient in the litter, and apparent excretion was the quantity of the nutrient found in the litter. Any appreciable difference between the true and apparent values would be an indication of the direction and magnitude of losses attributable to volatilization from the litter or contamination from the diet or drinking water. Using unaccounted for phosphorus as a nonvolatilized indicator of the sensitivity of this measurement (i.e., the difference between true and apparent excretion), an average of 9.5% error was associated with these measures. True retention values for phosphorus in grams per bird or percentage were relatively greater than the corresponding values from apparent retention. This may

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Sulfur   g/bird

Age (wk)

Apparent retention3

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NUTRIENT MASS BALANCE IN TURKEYS AT THREE AGES

Table 6. Nitrogen, phosphorus, sulfur, sodium, and potassium excretion in toms fed diets with (low-phosphorus diet) or without (industry diet) phytase1 True excretion2 Item

Age (wk)

Nitrogen   g/bird  % Phosphorus   g/bird  %

Sodium   g/bird  % Potassium   g/bird  % Calcium   g/bird  %

Industry

Low P4

SEM

Industry

Low P4

SEM

0 0 0 0 0 0

to to to to to to

12 15 18 12 15 18

388.0 641.4a 938.5 81.4 82.1 86.7

367.3 600.1b 905.1 80.6 81.8 83.1

17.80 18.89 47.35 0.95 0.26 2.60

205.4b 375.3a 481.8 44.1b 50.2a 46.8

234.5a 303.6b 472.9 53.3a 43.3b 46.1

17.00 12.04 47.69 2.84 1.94 3.66

0 0 0 0 0 0

to to to to to to

12 15 18 12 15 18

65.3a 116.0a 201.3a 52.8a 56.1a 67.2a

29.8b 50.9b 94.6b 32.9b 36.3b 46.1b

3.87 6.15 13.76 3.05 4.34 2.65

74.9a 138.9a 208.7a 58.1a 64.2a 65.8a

47.2b 74.7b 125.8b 51.5b 50.7b 57.9b

6.78 2.76 13.06 3.62 0.75 2.64

0 0 0 0 0 0

to to to to to to

12 15 18 12 15 18

8.7a 20.3a 37.9 30.0a 42.0a 54.6

6.6b 15.4b 35.5 24.3b 35.4b 54.7

0.86 0.96 3.68 2.14 1.15 2.59

13.7 26.0a 38.5a 47.5b 53.8 55.8a

13.4 22.3b 34.2b 51.0a 51.0 53.0b

1.21 1.26 2.77 2.64 2.13 2.54

0 0 0 0 0 0

to to to to to to

12 15 18 12 15 18

9.53 21.16 33.64 56.1 67.2 73.1

9.49 18.06 34.07 56.4 64.2 73.1

0.698 0.628 2.474 1.41 0.69 1.16

0 0 0 0 0 0

to to to to to to

12 15 18 12 15 18

123.7 209.7 305.9 81.9 84.4 86.9

119.5 193.1 292.1 81.1 84.0 86.3

0 0 0 0 0 0

to to to to to to

12 15 18 12 15 18

65.5a 124.6a 240.5a 41.4 46.4 62.2a

40.1b 55.3b 121.7b 30.9 28.3 43.0b

50.1 106.1 170.2 58.8 67.5 74.0

54.0 100.0 169.3 65.3 71.3 73.3

4.81 4.71 11.96 3.31 2.69 3.53

8.00 6.14 18.13 0.76 0.30 0.38

143.2 238.5 334.0 94.3 96.3 95.0

149.9 222.5 317.5 103.8 97.0 94.3

12.03 9.06 17.80 4.77 3.07 4.53

8.4 16.1 22.8 5.8 7.4 5.4

90.8a 165.3a 252.9a 56.3 61.0 65.8a

63.0b 89.7b 142.0b 51.0 45.5 49.8b

11.7 15.8 15.3 5.9 5.1 2.7

a,b

Means within row with no common superscripts differ (P < 0.05) Means represent 4 pens per diet (5 birds per pen). 2 Difference between mineral consumed in feed and mineral retained in carcass. 3 Mineral in litter. 4 Low-phosphorus diet plus supplemental phytase. 1

Table 7. Unaccounted for nutrients1,2 for turkey toms fed industry or low-phosphorus (low P) diets containing phytase resulting from the difference between true (feed nutrient – carcass nutrient) and apparent nutrient excretion (nutrient excreted in litter)3 P Age (wk)

N

S

Industry

Low P4

SEM

Industry

Low P4

SEM

Industry

Low P4

SEM

−7.4a −17.2 4.7a

−15.8b −20.7 −24.3b

5.78 7.13 10.85

176.2a 249.8b 427.2

125.6b 283.7a 404.7

14.95 19.98 52.16

9.2a 14.0a 21.63

7.2b 12.7b 22.0

0.75 0.92 2.30

−5.0 −8.5 1.0

−18.5 −14.3 −11.8

5.29 4.42 3.59

37.3a 32.0b 40.0

27.3b 38.3a 37.0

3.24 1.97 4.62

32.3a 29.3 31.8

27.3b 29.0 33.5

3.24 1.99 2.40

1

g/bird   0 to 12   0 to 15   0 to 18 %2   0 to 12   0 to 15   0 to 18 a,b

Means within row with no common superscripts differ (P < 0.05). Difference between true excretion (feed − carcass) and apparent excretion (litter). 2 Percentage of volatilization [(true excretion-apparent excretion/mineral intake) × 100]. 3 Means represent 4 pens per diet (5 birds per pen). 4 Low-phosphorus diet plus supplemental phytase. 1

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Sulfur   g/bird

Apparent excretion3

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Applegate et al. Table 8. Comparison of apparent nitrogen and phosphorus excretion of turkey toms fed an industry or a low-phosphorus diet containing phytase (low P) vs. apparent excretion predicted by the American Society for Agricultural and Biological Engineers manure production and characteristics standard (D384.2; ASABE, 2005)1 Nutrient Nitrogen (g/bird)   Industry

  Low P4

Phosphorus (g/bird)   Industry

ASABE predicted apparent excretion3

SEM

0 to 12 0 to 15 0 to 18

205.0 375.5a 481.8

196.8 322.3b 448.3

15.62 9.06 51.16

0 to 12 0 to 15 0 to 18

234.5a 303.8 473.0

188.0b 302.8 448.8

11.56 12.10 16.79

0 0 0 0 0 0

74.8 138.8a 208.8a 47.3 74.8 125.8a

64.8 107.8b 155.5b 46.3 73.3 107.3b

6.82 2.45 14.96 2.50 2.80 4.08

to to to to to to

12 15 18 12 15 18

a,b

Means within row with no common superscripts differ (P < 0.05) Means represent 4 pens per diet (5 birds per pen). 2 Nutrients in litter. 3 Values were predicted by using the percentages of nitrogen and phosphorus excretion of 41.24 and 52.02%, respectively, of total nitrogen and phosphorus intake. 4 Low-phosphorus diet plus supplemental phytase. 1

be a result of feed contamination in the litter, which may eventually have resulted in a greater phosphorus content in the litter. Phosphorus from the drinking water may also have contributed to observed differences. Feed contamination could also be responsible for the relatively low apparent sulfur retention values relative to the true value. Retention of sulfur increased with age (grams per bird), likely in part because of feather growth. Unlike phosphorus and sulfur, the apparent retention for nitrogen was more that 100% greater than the corresponding values for true retention. This observation indicates that a huge amount of nitrogen was unaccounted for at all 3 ages evaluated. Wu-Haan et al. (2007) noted, in measuring emissions from laying hens, that 99.7% of ammonia, nitrous oxide, and nitrogen dioxide emissions were as ammonia. Therefore, the overwhelming majority of unaccounted for nitrogen likely was emitted as ammonia in this study. This difference between apparent and true phosphorus excretion ranged between 1 and 18.5%. Unlike what was seen for phosphorus, however, the difference between true and apparent excretion for sulfur and nitrogen was a net loss. The loss was between 27 and 34% for sulfur and 27 and 40% for nitrogen. These minerals that could not be accounted for were assumed to have been lost as either hydrogen sulfide or ammonia. Further calculation shows that the unaccounted for nitrogen as a percentage of excreted nitrogen for the IND diet or LP diet for wk 12, 15, and 18 was 45 or 34, 39 or 47, and 46 or 45%, respectively. When comparing apparent excretion of nitrogen values, the predicted nitrogen excretion value (standard

D384.2; ASABE, 2005) based on literature reports (41.2%) was somewhat less than that in the current study (47.3%). This difference was not substantial and, on average, underestimated apparent nitrogen excretion by 8.1%. The predicted phosphorus excretion value (standard D384.2; ASABE, 2005) based on literature reports (52.0%) was numerically, but not significantly, different from that in the current study (58.05%). The estimated phosphorus excretion therefore underestimated phosphorus excretion by 17.2%. Much of this underestimation could be accounted for largely by birds fed the IND diets. In conclusion, the mass of phosphorus excreted at 0 to 12, 0 to 15, and 0 to 18 wk of age was 37, 46, and 40% greater for birds fed the IND diets compared with birds fed the LP diets. These results indicate that feeding birds more closely to nutrient requirements with supplemental phytase did not affect bird performance but could substantially reduce the amount of phosphorus excreted.

ACKNOWLEDGMENTS The research reported herein was sponsored in part by grants from the United States Poultry and Egg Association (Tucker, GA) and by United States Department of Agriculture funding through the Midwest Poultry Consortium (St. Paul, MN) and the Iowa Turkey Federation (Ames). The assistance of Pat Jaynes, Kristina Thompson, Darrin Karcher, and members of the Poultry Unit of the Purdue University Animal Science Research Center during weighing is acknowledged.

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  Low P4

Apparent excretion2

Age (wk)

NUTRIENT MASS BALANCE IN TURKEYS AT THREE AGES

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