Value of Non-Phosphorus Effects of Exogenous Phytase in Swine

ROMMEL C. SULABO Dept. of Animal Sciences & Industry Kansas State University Value of Non-Phosphorus Effects of Exogenous Phytase in Swine

Outline Introduction Phytase and protein/AA utilization Phytase and energy utilization Use of phytase matrix values Discussion Evaluation and conclusions

Introduction Wide acceptance of phytase use in pig and poultry diets: Increased environmental legislation Ban of animal origin P sources (e.g. EU) Lower feed enzyme inclusion costs relative to inorganic P sources Increasing ingredient costs (corn, SBM, etc.) More commercial sources of phytases Current ideas of phytase use: account for potential effects in improving protein/AA and energy utilization

Introduction Phytic acid: Myo-inositol hexakisphosphate Poly-anionic molecule with a tremendous capacity to bind positively-charged nutrients (‘chelating capacity’) Probable basis of its anti-nutritive properties

Thompson, 1988 Interactions of phytic acid with protein, minerals and starch Binary nutrient-phytate complex Ternary nutrient-mineral-phytate complex H O P O O O H O P OH O O H O P O O O H O P O O O H O P O O O H OH P O O O O O O CH 2 OH STARCH + Ca + + Ca + O C PROTEIN O CH 2 NH 3 CH 2 PROTEIN STARCH

Net Variable Cost (or Savings) with Phytase Supplementation Net Cost Change equals summation of: Added Cost > Cost of phytase > Cost of added ingredients due to phytase addition Added Returns > Value of reduced ingredient needs due to phytase > Value of reduced P excretion in pig manure

Nutrient matrix values of commercial phytases for pig diets Item Natuphos ® 5000 Ronozyme ® P5000 (CT) Phyzyme XP ® 5000 Optiphos ® 2000 Dose (U/kg) 500 750 500 250 Inclusion rate (g/ton) 100 150 100 125 Nutrient matrix Total P (%) 1111 342? 1329 - Available P (%) 1000 - 1196 960 Ca (%) 1000 232? 931 672 DE (kcal/kg) 98958 - 304398 - ME (kcal/kg) - - - 76000 Dig Protein (%) 2000 - 2444 1600 Dig Lys (%) 80 - 151 64 Dig Met (%) 25 - 46 20 Dig Cys (%) 30 - 102 - Dig Thr (%) 50 - 237 40 Dig Trp (%) 30 - 62 24 Dig Leu (%) 120 - 404 -

Introduction Rojas and Scott (1969) – first suggested the potential interaction between phytate and protein utilization in poultry Possible interactions 1 : Presence of protein-phytate complexes in feedstuffs De novo formation of binary and ternary protein-phytate complexes in the digestive tract Phytate inhibition of proteolytic enzymes (e.g. trypsin activity?) 1 Selle et al. (2000)

De novo formation of protein-phytate complexes Pre-bound dietary protein less readily digested Pigs: Stomach Poultry: Crop, Proventriculus, gizzard Small intestine Protein Phytate Proposed mode of action of phytate and phytase Reduced absorption of dietary AA and reduced re-absorption of endogenous AA Mucin loss Refractory to pepsin digestion Additional outputs of pepsin and HCl Extra mucin secretion Na + as NaHCO 3 Reduction of Na + -dependent transport and Na + -pump activity Compromised AA uptakes Selle et al. (2000)

Pig studies: Phytase vs. protein/AA utilization 1 Pig type: G = grower, N = nursery 2 Phytase: A. niger (N) – Natuphos ® 3 Method: PVTC = Post-valve T-cannulation, SICV = Steered-ileocecal valve T-cannulation T = Simple T-cannulation All studies used Latin square design with n number of pigs and periods Ave. adaptation period of 7 days (4-5 d adaptation to exptl. diets, 2 and 1-2 d for ileal digesta and fecal collection, respectively) No. Study n Pig type 1 Diet Phytase 2 Dose (FTU/kg) Method 3 Inert Marker 1 Mroz et al. (1994) 5 G C-Tapioca-SBM A. niger (N) 800 PVTC Cr 2 O 3 2 Johnston et al. (2004) 8 G C-SBM A. niger (N) 800 SICV Cr 2 O 3 3 Liao et al. (2005a)-1 6 N C-SBM A. niger (N) 500 T Cr 2 O 3 Liao et al. (2005a)-2 6 N Wheat-SBM A. niger (N) 500 T Cr 2 O 3 Liao et al. (2005a)-3 6 N Wheat-SBM-canola A. niger (N) 500 T Cr 2 O 3 Liao et al. (2005a)-4 6 N Barley-peas-canola A. niger (N) 500 T Cr 2 O 3 4 Liao et al. (2005b)-1 8 G C-Rice bran-SBM A. niger (N) 2000 T Cr 2 O 3 Liao et al. (2005b)-2 8 G C-SBM A. niger (N) 2000 T Cr 2 O 3 5 Radcliffe et al. (2006) 10 G C-SBM A. niger (N) 500 SICV Cr 2 O 3

Effect of exogenous phytase on AID of CP in complete diets fed to pigs Inclusion: 500 to 2000 U/kg

CP digestibility: Response (%) to phytase supplementation Phytase response (% of control)

Effect of exogenous phytase on AID of mean AA in complete diets fed to pigs Inclusion: 500 to 2000 U/kg

Phytase response (% of control) Mean AA digestibility: Response (%) to phytase supplementation

Effect of phytase supplementation on the AID (%) of CP and AA in corn- and wheat-SBM diets fed to nursery pigs Liao et al . (2005) n = 6 barrows; Phytase (Natuphos at 500 FTU/kg) No effect of phytase level (500 vs. 1000 U) Corn-SBM Wheat-SBM Control Phytase Response (%) Control Phytase Response (%) CP 0.76 0.76 0.26 0.83 0.84 0.36 Arg 0.86 0.87 0.46 0.89 0.89 0.56 His 0.84 0.83 -0.48 0.86 0.86 -0.23 Ile 0.79 0.81 1.51 0.86 0.86 -0.23 Leu 0.78 0.76 -2.44 0.86 0.86 0.00 Lys 0.76 0.76 -0.40 0.85 0.85 0.12 Phe 0.82 0.83 1.22 0.87 0.87 -0.12 Thr 0.73 0.73 0.00 0.78 0.78 -0.90 Val 0.76 0.77 1.06 0.84 0.83 -0.36

Effect of phytase supplementation on the AID (%) of CP and AA in wheat-SBM-canola meal and barley-peas-canola meal diets Liao et al . (2005) ; a P <0.05, b P <0.07 n = 6 barrows; Phytase (Natuphos at 500 FTU/kg) No effect of phytase level (500 vs. 1000 U) Wheat-SBM-Canola Barley-Peas-Canola Control Phytase Response (%) Control Phytase Response (%) CP 0.72 0.75 3.89 b 0.73 0.74 0.27 Arg 0.82 0.85 3.17 a 0.85 0.85 -0.23 His 0.82 0.85 4.16 a 0.84 0.82 -1.32 Ile 0.75 0.79 4.51 b 0.77 0.77 0.13 Leu 0.78 0.81 3.98 b 0.79 0.79 -0.13 Lys 0.77 0.80 4.42 b 0.82 0.82 0.24 Phe 0.78 0.82 4.99 a 0.80 0.80 -0.13 Thr 0.69 0.72 4.93 a 0.68 0.68 0.59 Val 0.73 0.77 5.18 a 0.74 0.74 0.00

Effect of reduction of dietary Ca and P and/or phytase addition on AID (%) of AA in diets for finishing pigs n = 8 barrows; Contrasts: a Diet 1 vs. 4 = P <.05, b Ca/aP = P <.06 Johnston et al . (2004) Diet No. 1 2 3 4 Ca, % 0.50 0.40 0.50 0.40 aP, % 0.19 0.09 0.19 0.09 Phytase, U/kg 0 0 500 500 SEM Lys 77.2 80.8 79.9 80.2 1.1 Ile ab 77.3 81.6 81.0 81.6 1.0 Leu ab 80.0 83.6 83.2 83.8 0.9 Phe ab 78.4 81.8 81.1 82.1 1.1 His 83.4 86.0 85.3 85.6 0.9 Arg a 85.7 87.1 86.9 88.3 0.8 Val ab 76.6 82.0 79.0 81.1 1.1 Thr ab 70.5 75.9 74.4 75.0 1.3 Trp 77.4 80.4 79.8 80.3 1.2

Effects of dietary phytase and CP on N balance in growing pigs n = 10 barrows; a Linear effect of protein level, P <.003 Radcliffe et al . (2006) Diet No. 1 2 3 4 5 Ca, % 0.44 0.44 0.44 0.44 0.44 P, % 0.40 0.40 0.40 0.40 0.40 CP, % 12.0 11.1 10.2 10.2 10.2 Phytase, U/kg 0 0 0 250 500 SEM N intake, g/d a 39.9 37.2 35.7 35.7 36.1 1.9 Fecal N, g/d 5.5 5.7 5.0 5.4 4.9 0.7 Urinary N, g/d 1.6 2.6 2.3 1.6 2.2 1.7 N digested, g/d a 34.4 31.6 30.7 30.3 31.2 1.9 N retained, g/d a 32.4 28.9 28.4 28.7 29.1 2.8 N digested, % 86.3 84.8 85.9 84.9 86.6 1.7 N retained, % 81.2 77.6 79.5 80.2 80.4 5.3

Effects of dietary phytase and CP on AID (%) of CP and AA in growing pigs n = 10 barrows; Radcliffe et al . (2006) a Linear effect of protein level, P <.005, b Linear effect of phytase, P <.07 Diet No. 1 2 3 4 5 Ca, % 0.44 0.44 0.44 0.44 0.44 P, % 0.40 0.40 0.40 0.40 0.40 CP, % 12.0 11.1 10.2 10.2 10.2 Phytase, U/kg 0 0 0 250 500 SEM CP ab 73.8 72.0 66.7 69.3 70.1 6.1 His a 83.9 82.3 80.4 80.7 81.7 3.6 Lys ab 79.4 78.2 72.7 76.3 76.0 5.5 Arg ab 87.1 85.8 84 85.3 85.9 3.1 Met a 79.8 78.6 75.8 77.2 78.0 4.4 Thr ab 72.3 70.3 66 68.2 70.0 6.7

Discussion Fewer published data on the effects of phytase addition on the ileal digestibility of AA in pigs vs. poultry Effect of exogenous phytase on AID of CP/AA digestibility in pigs: - Variable and small responses (mostly no effect) - Earlier study 1 : significant effect of phytase supplementation in 10 AA in slaughtered pigs vs. 4 AA in cannulated pigs (effect of method?) - Protein deposition studies – more appropriate method to determine effect of phytase on protein digestibility - Lack of data – no growth performance study evaluating phytase vs. protein utilization in pigs - No data evaluating effects of phytase on TID values in pigs 1 Kornegay et al . (1998)

Discussion N balance study: No effect of phytase on N retention in pigs 1 - Numerous broiler studies showed similar effects of phytase addition on N retention and protein efficiency ratio (PER) 2 Effect of dietary ingredients: Inconsistent effect of phytase addition in weanling pigs, positive effect only in wheat-SBM-canola meal diet - Largest theoretical response to phytase is expected when diet is high in phytate and low in intrinsic phytase activity - Liao et al. (2005b): no difference in AID of AA between high vs. low phytate diet - Phytate-P per se may not be a primary determinant; it may be the amount of AA complexed with phytate-P? 1 Radcliffe et al . (2006) 2 Ledoux and Firman (2001); Boling-Frankenbach et al. (2001)

Effect of exogenous phytase on flow and composition of endogenous AA losses Cowieson and Ravindran (2007): Evaluated the effects of supplemental phytase and phytate on flow and composition of endogenous protein in the ileum of 28-d old broilers Phytase effect – ameliorate effect of phytic acid in increasing ileal endogenous AA flow? Previous work showed that phytate ↑ and microbial phytase ↓ excretion of sialic acid, an endogenous compound associated with gastrointestinal mucin 1 May help explain the variability in AA responses to phytase and understand the mode of action in relation to AA 1 Cowieson et al . (2004)

a Phytic acid (purified source) added at 0, 8.5, 11.5 or 14.5 g/kg ; Microbial phytase (Phyzyme XP) at 0 or 0.1 kg (500 FTU) Experimental diets Casein diet EHC diet a Casein 180 - EHC - 200 Dextrose 670 647 Vegetable oil 50 50 Cellulose 35 35 DCP 24 24 Na-bicarbonate 20 20 K 2 HPO 4 12 12 Salt 4 4 Titanium oxide - 3 MgO 2 2 Mineral premix 2.5 2.5 Vitamin premix 0.5 0.5

Ileal endogenous flow of the sum of AA (mg/kg DMI) as affected by dietary phytate level and phytase Na-phytate added to synthetic diet, corresponds to 2.4, 3.2 and 4.0 g/kg phytate-P; Phyzyme XP ® Cowieson and Ravindran, 2007 Ileal endogenous AA flow (mg/kg DMI)

Amino acid (AA) composition of endogenous protein (g/100 g crude protein) in 28-d old broilers as influenced by dietary levels of phytate Amino acid composition (g/100 g CP) Increasing PA level influenced concentrations of Asp, Ser, Pro, Gly, Val, Leu, and His

Amino acid (AA) composition of endogenous protein (g/100 g crude protein) in 28-d old broilers as influenced by microbial phytase Amino acid composition (g/100 g CP) Phytase inclusion: = Asp, Thr, Ser, Gly, Cys = Glu, Ala, Val, Phe

Discussion Phytic acid (PA): ↑ flow of EAA and N with increasing phytate concentration Microbial phytase: ↓ inimical effects of phytic acid on endogenous AA flow at all dietary phytic acid levels Levels of PA and phytase: Both influenced the composition of endogenous protein PA also selectively increased flow of some endogenous protein sources more than others (Asp, Ser, Thr, Tyr) - Mucins – rich in Thr, Ser, Pro, Cys Effects on AA digestibility should be evaluated based in TID (or RID) to account for changes in amount (composition) of endogenous AA losses

Dietary AA content AA losses Non-specific or basal endogenous loss Specific endogenous loss Dietary loss Partitioning of total ileal output Mosenthin and Rademacher, 2003

Effect of inert markers Pig studies: all used chromic oxide as their inert marker for estimating nutrient flow Broiler studies: Phytase response was inconsistent (summary of 13 AA digestibility studies) Phytase responses were greater when either titanium oxide or acid-insoluble ash were used as dietary markers vs. chromic oxide Selle et al. (2006): attributed the choice of markers as a potential source of variability in AA responses to phytase

Effect of digestibility marker on average increase in mean AA digestibility in broilers fed diets with and without phytase Percent

Introduction Theoretical basis 1 : - Phytate bind starch via H bonding - Phytate has the capacity to inhibit α-amylase activity - Phytate reduces glucose absorption in humans Broiler studies: Positive effects on energy uitilization were reported 1 Effects of phytase on energy digestibility in pigs are rarely studied 1 Selle et al. (2006)

Pig studies: Phytase vs . energy utilization 1 Pig type: G = grower, N = nursery 2 Phytase: A. niger (N) – Natuphos ® , E. coli (P) – Phyzyme XP ® 3 Method: SICV = Steered-ileocecal valve T-cannulation, T = Simple T-cannulation All studies used Latin square design with n number of pigs and periods Ave. adaptation period of 7 days (4-5 d adaptation to exptl. diets, 2 and 1-2 d for ileal digesta and fecal collection, respectively) No. Study n Pig type 1 Diet Phytase 2 Dose (FTU/kg) Method 3 Inert Marker 1 Johnston et al. (2004) 8 G C-SBM A. niger (N) 800 SICV Cr 2 O 3 2 Liao et al. (2005a)-1 6 N C-SBM A. niger (N) 500 T Cr 2 O 3 Liao et al. (2005a)-2 6 N Wheat-SBM A. niger (N) 500 T Cr 2 O 3 Liao et al. (2005a)-3 6 N Wheat-SBM-canola A. niger (N) 500 T Cr 2 O 3 Liao et al. (2005a)-4 6 N Barley-peas-canola A. niger (N) 500 T Cr 2 O 3 3 Liao et al. (2005b)-1 8 G C-Rice bran-SBM A. niger (N) 2000 T Cr 2 O 3 Liao et al. (2005b)-2 8 G C-SBM A. niger (N) 2000 T Cr 2 O 3 4 Nortey et al. (2007) 18 G Wheat-wheat millrun-SBM E. coli (P) 500 T Cr 2 O 3

AID of energy (%) as affected by dietary phytase in pig diets Apparent ileal digestibility of GE (%) Ave: Control = 78.4 , Phytase = 79.4 (+1.0%)

Effect of dietary phytase on apparent fecal digestibility in weaned piglets n = 12 pigs/treatment; Kies et al . (2005) Control diet Phytase diet SEM P < DM, % 82.6 84.6 0.45 0.05 N, % 80.2 82.0 0.52 0.09 Crude fat, % 81.9 83.1 0.26 0.05 Crude ash, % 45.0 54.8 1.40 0.02 Energy, % 84.7 86.0 0.41 0.10

Effect of dietary phytase on energy intake, energy loss, and heat production in weaned piglets n = 12 pigs/treatment; Kies et al . (2005) Control diet Phytase diet SEM P < GE intake 1162 1162 2.8 0.84 DE intake 983 1000 6.8 0.19 ME intake 958 961 3.1 0.65 Urinary energy 19 32 5 0.17 Methane production 5.5 6.7 0.16 0.02 Total HP (H tot ) 638 640 3.2 0.66 Activity related HP (H act ) 123 122 1.5 0.55 Activity corrected HP (H rest ) 515 519 3.8 0.55 Total energy retention (RE) 213 249 24 0.37 Energy retention as protein (RE p ) 148 163 7 0.21 Energy retention as fat (RE f ) 65 86 17 0.46 ME for maintenance (ME m ) 459 469 5 0.25

Effect of phytase level and ME intake on protein, fat, and ash accretion of growing pigs n = 6 pigs/treatment; a Energy, P <.05 Shelton et al . (2003) Item 2.9 x M 3.2 x M SEM 0 500 0 500 Protein deposition, g/d 92.5 101.4 110.3 112 8.9 Fat deposition, g/d a 55.7 65.5 84.0 83.1 10.4 Ash deposition, g/d 14.6 11.6 17.0 14.6 3.1 Heat production, Mcal a 3.14 3.21 3.41 3.39 0.07 Ne m , Mcal/kg 1.45 1.50 1.55 1.53 0.04 Ne p , Mcal/kg 0.75 0.83 0.88 0.90 0.07 RE, Mcal a 39.8 46.0 54.8 53.9 5.0

Effect of diet on growth performance and ultrasound measurements of growing pigs n = 128 pigs blocked by weight and ancestry (RCBD), 8 reps/trt and 4 pigs per replication Diets: (1) C-SBM control and (2) C-SBM with 0.10% lower P and Ca + 500 U/kg phytase Shelton et al . (2003) Item Control Phytase SEM ADG, kg 0.85 0.84 0.02 ADFI, kg 1.92 1.85 0.04 G/F 0.44 0.45 0.01 Ultrasound measurements Initial LMA, cm 2 10.48 10.44 0.12 Final LMA, cm 2 17.28 17.58 0.25 Initial 10th-rib fat, cm 0.91 0.87 0.03 Final 10th-rib fat, cm 1.40 1.43 0.04 LMA difference, cm 2 6.83 7.11 0.21 10th-rib fat difference, cm 0.49 0.56 0.05

Discussion Effect of phytase on energy digestibility: 11/14 (80%) comparisons showed no response to phytase addition in pigs No effect of phytase addition on total energy retention (RE) in weaned pigs and growing pigs (for pigs fed 3.2 x M) Phytase addition increased fat deposition, HP, and RE numerically in growing pigs fed 2.9 x M No effect of phytase addition on growth performance and ultrasound measurements in finishing pigs

3. Use of phytase matrix values

Using nutrient matrix values Maintain performance at lower feed cost Optimize least cost formulation using the nutrient equivalencies for P, Ca, AA and energy from X amount of phytase “ Down-spec” or enter phytase a a feed ingredient with nutrient values Reduce feed cost and improve performance Incorporate X amount of phytase to replace P and Ca from mineral sources; plus utilize extra nutients released to realize benefit in performance

Nutrient matrix values used in the study Natuphos 1200 added at 0.05% of the diet, 500 FTU/kg Nutrient Matrix value Amount provided in the diet Available P, % 188 0.094 Ca, % 188 0.094 CP, % 427 0.214 Lys, % 29 0.015 Met, % 5 0.003 Cys, % 10 0.005 SAA, % 15 0.008 Trp, % 6 0.003 Nutrient Matrix value Amount provided in the diet Thr, % 24 0.012 Val, % 26 0.013 Ile, % 22 0.011 Leu, % 33 0.017 Arg, % 16 0.008 Phe, % 21 0.011 His, % 11 0.006 ME, kcal/kg 61937 30.969

Growth performance of broilers using nutrient matrix for AA, Ca, and aP Data are means of 7 reps of 6 broilers/rep (14 d trial); ab P <.03 Diet 2 deficient in AA = 0.82% TID Lys (vs. 1.12%), rest of AA met or exceeded ratio to Lys Diet 3 = Diet 2 + phytase with nutrient matrix values for AA, Ca, and aP Diet 4 = Diet 3 with no phytase but with supplemental Ca and P Shelton et al . (2004) Treatment ADG ADFI G/F 1. C-SBM control diet 41.3 a 51.4 a 0.80 a 2. C-SBM deficient in AA 33.9 b 49.0 a 0.69 b 3. C-SBM diet deficient in AA but with 600 FTU/kg 33.2 b 49.0 a 0.68 b 4. Diet 3 without phytase but adequate in Ca and aP 33.1 b 48.6 b 0.68 b SEM 0.7 0.8 0.01

Growth performance of broilers using nutrient matrix for ME, Ca, and aP Data are means of 7 reps of 6 broilers/rep (14 d trial); ab P <.04 Diet 2 low in ME = 2937 kcal ME/kg (vs. 3200), Diet 3 = Diet 2 + phytase with nutrient matrix values for ME, Ca, and aP Diet 4 = Diet 3 with no phytase but with supplemental Ca and P Shelton et al . (2004) Treatment ADG ADFI G/F 1. C-SBM diet (Control) 41.3 a 51.4 0.80 a 2. C-SBM diet low in ME 38.1 b 51.9 0.74 b 3. C-SBM diet low in ME but with 600 FTU/kg 39.3 b 52.6 0.75 b 4. Diet 3 without phytase but adequate in Ca and aP 38.8 b 52.7 0.74 b SEM 0.6 0.9 0.01

Effect of dietary phytase on growth performance of 42-d old broilers N = 1575; Data are means of 10 reps of 105 broilers/rep Starter (0-15 d), Grower (16-35 d), Finisher (36-42 d) Diet 1 = C-SBM control diet Diet 2 = Diet 1 + 600 FTU/kg phytase with nutrient matrix values for ME, Ca, and aP Diet 3 = Diet 1 + 600 FTU/kg phytase with nutrient matrix values for ME, AA, Ca, and aP Shelton et al . (2004) Item 1 2 3 SEM Control ME ME and AA Final weight, g 2220 2201 2189 13.2 ADG, g 51.7 51.3 51.0 0.3 Feed intake, g 94.1 92.8 92.0 1 Gain:feed, g:kg 549 550 552 5 Tibia ash, % 57.27 58.02 57.12 0.56

Effect of dietary phytase on carcass traits of 42-d old broilers N = 1575; Data are means of 10 reps of 105 broilers/rep Shelton et al . (2004) 1 2 3 Item Control ME ME and AA SEM LW, kg 2.2 2.15 2.17 0.03 Eviscerated weight, kg 1.58 1.53 1.55 0.02 Chill weight, kg 1.62 1.57 1.58 0.02 Carcass yield, % 72.1 71.8 71.3 0.3 Moisture gain due to chill, % 2.54 2.35 2.32 0.27 24-h moisture loss, % 1.1 1.07 1.05 0.08 Breast weight PLW, % 13.3 12.7 13.1 0.14

Discussion Reducing AA or ME concentration in broiler diets resulted in decreased performance; phytase addition did not affect growth of broilers fed diets deficient in AA or ME Using nutrient matrix values for phytase in formulating C-SBM diets for broilers resulted in similar growth performance and carcass traits Authors: “matrix values are accurate and can be used in formulating diets for commercial broilers”

Basis of Natuphos ® AA matrix values

Conclusions Consistent response in improving P utilization by microbial phytase supplementation Current body of evidence: Inconsistent and mostly lacking in any microbial phytase-induced improvement in protein/AA and energy utilization Conflicting base of information

Implications Cost effectiveness of phytase addition can be improved if phytase can consistently  protein/AA and energy utilization Lack of response in pigs - caution needed in using over simplistic guidelines (“AA and energy matrix values”) Several factors merit further research

Value of Non-Phosphorus Effects of Exogenous Phytase in Swine

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Value of Non-Phosphorus Effects of Exogenous Phytase in Swine