TY - JOUR
AU - de Lange, C. F. M.
AB - ABSTRACT The application of phytase in conventional dry swine diets has been shown to improve P availability and utilization. The effectiveness of phytase may be further improved by steeping feedstuffs with phytase before feeding. A study was conducted to determine the value of steeping high-moisture corn (HMC) with phytase in P-deficient liquid diets for starter pigs. A total of 384 pigs were weaned at 19 to 23 d of age and 6.7 ± 0.1 kg of BW. Pigs were randomly assigned to pens, with 8 barrows and 8 gilts per pen and 5 pens per dietary treatment (only 4 pens for the control treatment). The 5 dietary treatments (all HMC-based 3-phase feeding programs) were 1) negative control with no added phytase, 2 and 3) negative control with phytase added to the HMC to achieve 62.5 or 125 phytase units (FTU)/kg of HMC (DM basis) of phytase added to the HMC and allowed to steep for 24 h before feeding, and 4 and 5) negative control with the same amount of phytase added to the base mix without steeping before feeding. Total P content (88% DM basis) averaged 0.49% in phase I and 0.37% in phase II and III diets. Individual pig BW and per pen ADFI were measured on a weekly basis. Apparent total tract digestibility of DM, OM, CP, P, and Ca were measured using titanium dioxide as an indigestible marker in phase III diets. At the end of the study (7 wk postweaning), 4 pigs from each pen were killed for assessment of body composition, breaking strength and mineral content of metacarpals, total and soluble P content in duodenal digesta, and urinary P content. There was no effect of added phytase on ADG, ADFI, or G:F. The soluble P:total P ratio in duodenal digesta was increased with the addition of phytase (P < 0.05). Steeping HMC with phytase resulted in greater digestibility of DM and CP (P < 0.01). A trend toward increased digestibility of Ca with added phytase was observed (P = 0.07), but there was no effect of dietary treatment on P digestibility. Urinary P content was considerably greater in pigs fed diets with exogenous phytase (P < 0.05). Additional phytase resulted in increased P and Ca content in the empty body (P < 0.05). Metacarpal content of P (P < 0.05) and Ca (P = 0.07) and breaking strength (P < 0.05) were improved with added phytase. Despite a lack of effect on P digestibility, added phytase improved retention of Ca and P in starter pigs fed P-deficient HMC-based liquid diets. There was little benefit from steeping HMC with phytase before feeding. INTRODUCTION In grains, most P is bound in the form of phytate (NRC, 1998), reducing its availability to pigs. The addition of phytase to conventional dry diets has been shown to improve P availability and utilization in pigs. However, apparent fecal P digestibility rarely exceeds 55% under these conditions (Kornegay and Verstegen, 2001). The response to exogenous phytase may be constrained by feed retention time in the stomach (Schlemmer et al., 2001) and inappropriate conditions in the gastrointestinal tract of the pig (Kemme et al., 2006). Liquid feeding provides opportunities to enhance the feeding value of feedstuffs for pigs (Brooks et al., 2001). In grains with intrinsic phytase activity, phytate degradation and P availability may be increased by soaking grains in water (Skoglund et al., 1997). Corn, however, has negligible intrinsic phytase activity (Poulsen, 2000). It has been shown that steeping of high-moisture corn (HMC) with added phytase results in release of almost all phytate P (Niven et al., 2007). Also, Liu et al. (1997) showed that the efficacy of exogenous phytase in corn and soybean meal-based grower pig diets was increased when diets were fed in a liquid form. The response to 250 phytase units (FTU)/kg of added phytase in liquid diets was equivalent to 500 FTU/kg in dry diets in terms of ADG and nutrient absorption (Liu et al., 1997). To our knowledge, the effect of steeping individual feed ingredients with added phytase on P utilization in pigs has not been investigated. It was hypothesized that steeping HMC with small amounts of phytase for a minimum of 24 h before feeding would result in improved growth performance and nutrient utilization in pigs, when compared with adding phytase immediately before liquid feed preparation and delivery. The objectives of the current study were to determine the phytase activity required for maximum release of P in HMC and the impact of steeping HMC with phytase in P-deficient liquid diets on growth performance and nutrient utilization in starter pigs. MATERIALS AND METHODS The experimental protocol was reviewed and approved by the Animal Care Committee of the University of Guelph. Pigs were cared for according to the guidelines of the Canadian Council on Animal Care (1993). In Vitro Release of Phytate P in HMC with Added Phytase An in vitro steeping study was performed to determine the least amount of phytase activity that would result in maximum release of phytate P in HMC. The procedures for this in vitro study were described previously in detail by Niven et al. (2007). Briefly, HMC was mixed with water in a ratio of 1:2 (wt/vol) and placed in sterilized, 500-mL Nalgene bottles. Phytase [Ronozyme P (CT) 2500, DSM Nutritional Products Canada Inc., Ayr, Ontario, Canada] was added to the mixture at 0, 62.5, 125, 250, or 500 FTU/kg of DM. Triplicate samples were placed in an incubator at 25°C under continuous agitation at 230 rpm. Sub-samples were taken at 0, 1, 2, 4, 6, 9, 12, and 24 h after addition of phytase and were immediately frozen at –20°C. Samples were later thawed and centrifuged at 17,000 × g for 6 min at 4°C. The supernatant was analyzed for soluble P content to determine release of phytate P (Niven et al., 2007). Growth Performance Study A total of 384 purebred Yorkshire pigs were weaned at 19 to 23 d of age and 6.7 ± 0.24 kg of BW. They were randomly assigned to 24 wean-to-finish pens (396 × 198 cm) with 8 barrows and 8 gilts per pen (balanced for similar initial BW and litter mates across treatments) at the University of Guelph's Arkell Swine Research Station (Guelph, Ontario, Canada). A 3-phase feeding program with HMC and soybean meal-based diets was used, with gradual transitions between phases occurring from d 7 to 9 and 21 to 23 postweaning. Feed ingredients other than HMC were supplied from base mixes (Table 1). The dietary treatments were 1) negative control with no added phytase (NC), 2) NC with a low level of phytase (62.5 FTU/kg of HMC on a DM basis) added to HMC and allowed to steep for 24 h before feeding (LS), 3) NC with a high level of phytase (125 FTU/kg of HMC on a DM basis) added to HMC and allowed to steep for 24 h before feeding (HS), 4) NC with the low level of phytase added to the base mix and not steeped before feeding (LNS), and 5) NC with the high level of phytase added to the base mix and not steeped before feeding (HNS). Diets were formulated to be similar in DM and nutrient content within each phase and to meet or exceed NRC (1998) nutrient requirements for starter pigs, except for P and Ca (Table 2). No inorganic P was added to the diets and limestone was added to achieve a Ca to P ratio between 1:1 and 1.4:1 in all diets. Diets were formulated using nutrient contents of ingredients according to NRC (1998), except for Ca and P content in HMC and fish meal. Total P and Ca content in a representative sample of HMC were determined to be 0.33 and 0.07% (88% DM basis), respectively. The nutrient content of fish meal has been found to vary considerably from published values, and therefore a representative sample of the batch used in this study was analyzed before the study. The sample contained 7.34% Ca and 3.88% P (88% DM basis). The phase III diets contained 0.10% titanium dioxide (Sigma-Aldrich Corporation, St. Louis, MO) as an indigestible marker for determining apparent total tract digestibility of DM, OM, CP, P, and Ca, as well as apparent ileal digestibility of P. The diets did not contain any growth-promoting feed additives. Table 1. Ingredient composition (as-fed basis) of starter pig base mixes1 Ingredient, %  Phase I  Phase II  Phase III  NC  HNS  NC  HNS  NC  HNS  Wheat  17.49  17.49  22.05  22.04  25.13  25.12  Whey, dried2  35.01  35.01  21.84  21.84  —  —  Animal/vegetable fat blend3  3.50  3.50  4.37  4.37  5.02  5.02  Fishmeal, herring4  7.00  7.00  —  —  —  —  Blood plasma5  7.00  7.00  —  —  —  —  Soy protein concentrate  —  —  8.74  8.74  —  —  Soybean meal, dehulled  26.26  26.26  37.13  37.13  62.80  62.80  L-Lys  0.53  0.53  1.09  1.09  1.13  1.13  DL-Met  0.26  0.26  0.44  0.44  0.40  0.40  L-Thr  0.18  0.18  0.44  0.44  0.45  0.45  L-Trp  0.05  0.05  0.07  0.07  —  —  Limestone  1.49  1.49  2.08  2.08  2.56  2.56  Salt  0.35  0.35  0.66  0.66  1.00  1.00  Vitamin/mineral premix6  0.88  0.88  1.09  1.09  1.26  1.26  Titanium dioxide  —  —  —  —  0.25  0.25  Phytase7  —  0.0037  —  0.0059  —  0.0075  Ingredient, %  Phase I  Phase II  Phase III  NC  HNS  NC  HNS  NC  HNS  Wheat  17.49  17.49  22.05  22.04  25.13  25.12  Whey, dried2  35.01  35.01  21.84  21.84  —  —  Animal/vegetable fat blend3  3.50  3.50  4.37  4.37  5.02  5.02  Fishmeal, herring4  7.00  7.00  —  —  —  —  Blood plasma5  7.00  7.00  —  —  —  —  Soy protein concentrate  —  —  8.74  8.74  —  —  Soybean meal, dehulled  26.26  26.26  37.13  37.13  62.80  62.80  L-Lys  0.53  0.53  1.09  1.09  1.13  1.13  DL-Met  0.26  0.26  0.44  0.44  0.40  0.40  L-Thr  0.18  0.18  0.44  0.44  0.45  0.45  L-Trp  0.05  0.05  0.07  0.07  —  —  Limestone  1.49  1.49  2.08  2.08  2.56  2.56  Salt  0.35  0.35  0.66  0.66  1.00  1.00  Vitamin/mineral premix6  0.88  0.88  1.09  1.09  1.26  1.26  Titanium dioxide  —  —  —  —  0.25  0.25  Phytase7  —  0.0037  —  0.0059  —  0.0075  1Base mixes were used in the preparation of complete diets for negative control with no added phytase (NC) and NC with 125 phytase units (FTU) of phytase/kg of high-moisture corn (DM basis) added to the base mix and not steeped before feeding (HNS). Combinations of these base mixes were used to generate diets for all dietary treatments. 211982409 (Saputo, St. Leonard, Québec, Canada). 3Lacta-Fat (Kenpal Farm Products Inc., Centralia, Ontario, Canada). 4CO1090F (Swimco, Georgetown, Ontario, Canada). 5AP920 (American Protein Corporation, Ames, IA). 6Supplied per kilogram of complete diet: vitamin A, 10,000 IU as retinyl acetate (2.5 mg) and retinyl palmitate (1.7 mg); vitamin D3, 1,000 IU as cholecalciferol; vitamin E, 56 IU as DL-α-tocopherol acetate (44 mg); vitamin K, 2.5 mg as menadione; choline, 500 mg; pantothenic acid, 15 mg; riboflavin, 5 mg; folic acid, 2 mg; niacin, 25 mg; thiamine, 1.5 mg; vitamin B6, 1.5 mg; biotin, 0.2 mg; vitamin B12, 0.025 mg; Se, 0.3 mg from Na2SeO3; Cu, 15 mg from CuSO4∙5H2O; Zn, 104 mg from ZnO; Fe, 100 mg from FeSO4; Mn, 19 mg from MnO2; and I, 0.3 mg from KI (DSM Nutritional Products Canada Inc., Ayr, Ontario, Canada). 7Ronozyme P (CT) 2500, 2,500 FTU/g activity (DSM Nutritional Products Canada Inc.); added at the expense of wheat. View Large Table 1. Ingredient composition (as-fed basis) of starter pig base mixes1 Ingredient, %  Phase I  Phase II  Phase III  NC  HNS  NC  HNS  NC  HNS  Wheat  17.49  17.49  22.05  22.04  25.13  25.12  Whey, dried2  35.01  35.01  21.84  21.84  —  —  Animal/vegetable fat blend3  3.50  3.50  4.37  4.37  5.02  5.02  Fishmeal, herring4  7.00  7.00  —  —  —  —  Blood plasma5  7.00  7.00  —  —  —  —  Soy protein concentrate  —  —  8.74  8.74  —  —  Soybean meal, dehulled  26.26  26.26  37.13  37.13  62.80  62.80  L-Lys  0.53  0.53  1.09  1.09  1.13  1.13  DL-Met  0.26  0.26  0.44  0.44  0.40  0.40  L-Thr  0.18  0.18  0.44  0.44  0.45  0.45  L-Trp  0.05  0.05  0.07  0.07  —  —  Limestone  1.49  1.49  2.08  2.08  2.56  2.56  Salt  0.35  0.35  0.66  0.66  1.00  1.00  Vitamin/mineral premix6  0.88  0.88  1.09  1.09  1.26  1.26  Titanium dioxide  —  —  —  —  0.25  0.25  Phytase7  —  0.0037  —  0.0059  —  0.0075  Ingredient, %  Phase I  Phase II  Phase III  NC  HNS  NC  HNS  NC  HNS  Wheat  17.49  17.49  22.05  22.04  25.13  25.12  Whey, dried2  35.01  35.01  21.84  21.84  —  —  Animal/vegetable fat blend3  3.50  3.50  4.37  4.37  5.02  5.02  Fishmeal, herring4  7.00  7.00  —  —  —  —  Blood plasma5  7.00  7.00  —  —  —  —  Soy protein concentrate  —  —  8.74  8.74  —  —  Soybean meal, dehulled  26.26  26.26  37.13  37.13  62.80  62.80  L-Lys  0.53  0.53  1.09  1.09  1.13  1.13  DL-Met  0.26  0.26  0.44  0.44  0.40  0.40  L-Thr  0.18  0.18  0.44  0.44  0.45  0.45  L-Trp  0.05  0.05  0.07  0.07  —  —  Limestone  1.49  1.49  2.08  2.08  2.56  2.56  Salt  0.35  0.35  0.66  0.66  1.00  1.00  Vitamin/mineral premix6  0.88  0.88  1.09  1.09  1.26  1.26  Titanium dioxide  —  —  —  —  0.25  0.25  Phytase7  —  0.0037  —  0.0059  —  0.0075  1Base mixes were used in the preparation of complete diets for negative control with no added phytase (NC) and NC with 125 phytase units (FTU) of phytase/kg of high-moisture corn (DM basis) added to the base mix and not steeped before feeding (HNS). Combinations of these base mixes were used to generate diets for all dietary treatments. 211982409 (Saputo, St. Leonard, Québec, Canada). 3Lacta-Fat (Kenpal Farm Products Inc., Centralia, Ontario, Canada). 4CO1090F (Swimco, Georgetown, Ontario, Canada). 5AP920 (American Protein Corporation, Ames, IA). 6Supplied per kilogram of complete diet: vitamin A, 10,000 IU as retinyl acetate (2.5 mg) and retinyl palmitate (1.7 mg); vitamin D3, 1,000 IU as cholecalciferol; vitamin E, 56 IU as DL-α-tocopherol acetate (44 mg); vitamin K, 2.5 mg as menadione; choline, 500 mg; pantothenic acid, 15 mg; riboflavin, 5 mg; folic acid, 2 mg; niacin, 25 mg; thiamine, 1.5 mg; vitamin B6, 1.5 mg; biotin, 0.2 mg; vitamin B12, 0.025 mg; Se, 0.3 mg from Na2SeO3; Cu, 15 mg from CuSO4∙5H2O; Zn, 104 mg from ZnO; Fe, 100 mg from FeSO4; Mn, 19 mg from MnO2; and I, 0.3 mg from KI (DSM Nutritional Products Canada Inc., Ayr, Ontario, Canada). 7Ronozyme P (CT) 2500, 2,500 FTU/g activity (DSM Nutritional Products Canada Inc.); added at the expense of wheat. View Large Table 2. Ingredient composition (as-fed basis) and calculated energy and nutrient content (adjusted to 88% DM basis) of high-moisture corn (HMC)-based starter pig diets1 Item  Phase I2  Phase II2  Phase III2  NC  LNS  HNS  LS  HS  NC  LNS  HNS  LS  HS  NC  LNS  HNS  LS  HS  Ingredient, %                                HMC  42.9  42.8  42.9  —  —  54.2  54.2  54.2  —  —  60.2  60.2  60.2  —  —  HMC + 62.53  —  —  —  42.9  —  —  —  —  54.2  —  —  —  —  60.2  —  HMC + 1253  —  —  —  —  42.9  —  —  —  —  54.2  —  —  —  —  60.2  Base mixes                                           Phase I NC  57.1  28.5  —  57.1  57.1  —  —  —  —  —  —  —  —  —  —   Phase I HNS  —  28.5  57.1  —  —  —  —  —  —  —  —  —  —  —  —   Phase II NC  —  —  —  —  —  45.8  22.9  —  45.8  45.8  —  —  —  —  —   Phase II HNS  —  —  —  —  —  —  22.9  45.8  —  —  —  —  —  —  —   Phase III NC  —  —  —  —  —  —  —  —  —  —  39.8  19.9  —  39.8  39.8   Phase III HNS  —  —  —  —  —  —  —  —  —  —  —  19.9  39.8  —  —  Calculated energy  and nutrient content4                                           DE, MJ/kg  14.6  14.6  14.6  14.6  14.6  14.7  14.7  14.7  14.7  14.7  14.8  14.8  14.8  14.8  14.8   Ca, %  0.85  0.85  0.85  0.85  0.85  0.55  0.55  0.55  0.55  0.55  0.51  0.51  0.51  0.51  0.51   Total P, %  0.61  0.61  0.61  0.61  0.61  0.42  0.42  0.42  0.42  0.42  0.40  0.40  0.40  0.40  0.40   Available P,5 %  0.42  0.42  0.42  0.46  0.49  0.20  0.20  0.20  0.25  0.26  0.15  0.15  0.15  0.20  0.22   Ca:P  1.39  1.39  1.39  1.39  1.39  1.31  1.31  1.31  1.31  1.31  1.28  1.28  1.28  1.28  1.28   CP, %  21.7  21.7  21.7  21.7  21.7  19.7  19.7  19.7  19.7  19.7  20.1  20.1  20.1  20.1  20.1   Total Lys, %  1.51  1.51  1.51  1.51  1.51  1.32  1.32  1.32  1.32  1.32  1.29  1.29  1.29  1.29  1.29   SID6 Lys, %  1.36  1.36  1.36  1.36  1.36  1.21  1.21  1.21  1.21  1.21  1.17  1.17  1.17  1.17  1.17  Item  Phase I2  Phase II2  Phase III2  NC  LNS  HNS  LS  HS  NC  LNS  HNS  LS  HS  NC  LNS  HNS  LS  HS  Ingredient, %                                HMC  42.9  42.8  42.9  —  —  54.2  54.2  54.2  —  —  60.2  60.2  60.2  —  —  HMC + 62.53  —  —  —  42.9  —  —  —  —  54.2  —  —  —  —  60.2  —  HMC + 1253  —  —  —  —  42.9  —  —  —  —  54.2  —  —  —  —  60.2  Base mixes                                           Phase I NC  57.1  28.5  —  57.1  57.1  —  —  —  —  —  —  —  —  —  —   Phase I HNS  —  28.5  57.1  —  —  —  —  —  —  —  —  —  —  —  —   Phase II NC  —  —  —  —  —  45.8  22.9  —  45.8  45.8  —  —  —  —  —   Phase II HNS  —  —  —  —  —  —  22.9  45.8  —  —  —  —  —  —  —   Phase III NC  —  —  —  —  —  —  —  —  —  —  39.8  19.9  —  39.8  39.8   Phase III HNS  —  —  —  —  —  —  —  —  —  —  —  19.9  39.8  —  —  Calculated energy  and nutrient content4                                           DE, MJ/kg  14.6  14.6  14.6  14.6  14.6  14.7  14.7  14.7  14.7  14.7  14.8  14.8  14.8  14.8  14.8   Ca, %  0.85  0.85  0.85  0.85  0.85  0.55  0.55  0.55  0.55  0.55  0.51  0.51  0.51  0.51  0.51   Total P, %  0.61  0.61  0.61  0.61  0.61  0.42  0.42  0.42  0.42  0.42  0.40  0.40  0.40  0.40  0.40   Available P,5 %  0.42  0.42  0.42  0.46  0.49  0.20  0.20  0.20  0.25  0.26  0.15  0.15  0.15  0.20  0.22   Ca:P  1.39  1.39  1.39  1.39  1.39  1.31  1.31  1.31  1.31  1.31  1.28  1.28  1.28  1.28  1.28   CP, %  21.7  21.7  21.7  21.7  21.7  19.7  19.7  19.7  19.7  19.7  20.1  20.1  20.1  20.1  20.1   Total Lys, %  1.51  1.51  1.51  1.51  1.51  1.32  1.32  1.32  1.32  1.32  1.29  1.29  1.29  1.29  1.29   SID6 Lys, %  1.36  1.36  1.36  1.36  1.36  1.21  1.21  1.21  1.21  1.21  1.17  1.17  1.17  1.17  1.17  1Dietary treatments were 1) negative control with no added phytase (NC), 2) NC with 62.5 phytase units (FTU) of phytase/kg of HMC (DM basis) added to HMC and allowed to steep for 24 h before feeding (LS), 3) NC with 125 FTU of phytase/kg of HMC (DM basis) added to HMC and allowed to steep for 24 h before feeding (HS), 4) NC with 62.5 FTU of phytase/kg of HMC (DM basis) added to the base mix and not steeped before feeding (LNS), and 5) NC with 125 FTU of phytase/kg of HMC (DM basis) added to the base mix and not steeped before feeding (HNS). 2Pigs were placed on a 3-phase feeding program with transitions to phase II and III diets occurring from d 7 to 9 and 21 to 23 postweaning, respectively. 3Added phytase given as FTU/kg of HMC on a DM basis [(Ronozyme P (CT) 2500, DSM Nutritional Products Canada Inc., Ayr, Ontario, Canada]. 4Energy and nutrient content of complete diets were estimated based on published energy and nutrient contents of feed ingredients according to NRC (1998), except for HMC (P, 0.33%; Ca, 0.07%) and fish meal (P, 3.88%; Ca, 7.34%), and expressed on an 88% DM basis. 5Based on P availability in ingredients according to NRC (1998) and measured P solubility (assumed to represent availability) in representative samples of stored HMC. For treatments LS and HS, available P also represents increases in P solubility observed during in vitro steeping of HMC with phytase. 6Standardized ileal digestible. View Large Table 2. Ingredient composition (as-fed basis) and calculated energy and nutrient content (adjusted to 88% DM basis) of high-moisture corn (HMC)-based starter pig diets1 Item  Phase I2  Phase II2  Phase III2  NC  LNS  HNS  LS  HS  NC  LNS  HNS  LS  HS  NC  LNS  HNS  LS  HS  Ingredient, %                                HMC  42.9  42.8  42.9  —  —  54.2  54.2  54.2  —  —  60.2  60.2  60.2  —  —  HMC + 62.53  —  —  —  42.9  —  —  —  —  54.2  —  —  —  —  60.2  —  HMC + 1253  —  —  —  —  42.9  —  —  —  —  54.2  —  —  —  —  60.2  Base mixes                                           Phase I NC  57.1  28.5  —  57.1  57.1  —  —  —  —  —  —  —  —  —  —   Phase I HNS  —  28.5  57.1  —  —  —  —  —  —  —  —  —  —  —  —   Phase II NC  —  —  —  —  —  45.8  22.9  —  45.8  45.8  —  —  —  —  —   Phase II HNS  —  —  —  —  —  —  22.9  45.8  —  —  —  —  —  —  —   Phase III NC  —  —  —  —  —  —  —  —  —  —  39.8  19.9  —  39.8  39.8   Phase III HNS  —  —  —  —  —  —  —  —  —  —  —  19.9  39.8  —  —  Calculated energy  and nutrient content4                                           DE, MJ/kg  14.6  14.6  14.6  14.6  14.6  14.7  14.7  14.7  14.7  14.7  14.8  14.8  14.8  14.8  14.8   Ca, %  0.85  0.85  0.85  0.85  0.85  0.55  0.55  0.55  0.55  0.55  0.51  0.51  0.51  0.51  0.51   Total P, %  0.61  0.61  0.61  0.61  0.61  0.42  0.42  0.42  0.42  0.42  0.40  0.40  0.40  0.40  0.40   Available P,5 %  0.42  0.42  0.42  0.46  0.49  0.20  0.20  0.20  0.25  0.26  0.15  0.15  0.15  0.20  0.22   Ca:P  1.39  1.39  1.39  1.39  1.39  1.31  1.31  1.31  1.31  1.31  1.28  1.28  1.28  1.28  1.28   CP, %  21.7  21.7  21.7  21.7  21.7  19.7  19.7  19.7  19.7  19.7  20.1  20.1  20.1  20.1  20.1   Total Lys, %  1.51  1.51  1.51  1.51  1.51  1.32  1.32  1.32  1.32  1.32  1.29  1.29  1.29  1.29  1.29   SID6 Lys, %  1.36  1.36  1.36  1.36  1.36  1.21  1.21  1.21  1.21  1.21  1.17  1.17  1.17  1.17  1.17  Item  Phase I2  Phase II2  Phase III2  NC  LNS  HNS  LS  HS  NC  LNS  HNS  LS  HS  NC  LNS  HNS  LS  HS  Ingredient, %                                HMC  42.9  42.8  42.9  —  —  54.2  54.2  54.2  —  —  60.2  60.2  60.2  —  —  HMC + 62.53  —  —  —  42.9  —  —  —  —  54.2  —  —  —  —  60.2  —  HMC + 1253  —  —  —  —  42.9  —  —  —  —  54.2  —  —  —  —  60.2  Base mixes                                           Phase I NC  57.1  28.5  —  57.1  57.1  —  —  —  —  —  —  —  —  —  —   Phase I HNS  —  28.5  57.1  —  —  —  —  —  —  —  —  —  —  —  —   Phase II NC  —  —  —  —  —  45.8  22.9  —  45.8  45.8  —  —  —  —  —   Phase II HNS  —  —  —  —  —  —  22.9  45.8  —  —  —  —  —  —  —   Phase III NC  —  —  —  —  —  —  —  —  —  —  39.8  19.9  —  39.8  39.8   Phase III HNS  —  —  —  —  —  —  —  —  —  —  —  19.9  39.8  —  —  Calculated energy  and nutrient content4                                           DE, MJ/kg  14.6  14.6  14.6  14.6  14.6  14.7  14.7  14.7  14.7  14.7  14.8  14.8  14.8  14.8  14.8   Ca, %  0.85  0.85  0.85  0.85  0.85  0.55  0.55  0.55  0.55  0.55  0.51  0.51  0.51  0.51  0.51   Total P, %  0.61  0.61  0.61  0.61  0.61  0.42  0.42  0.42  0.42  0.42  0.40  0.40  0.40  0.40  0.40   Available P,5 %  0.42  0.42  0.42  0.46  0.49  0.20  0.20  0.20  0.25  0.26  0.15  0.15  0.15  0.20  0.22   Ca:P  1.39  1.39  1.39  1.39  1.39  1.31  1.31  1.31  1.31  1.31  1.28  1.28  1.28  1.28  1.28   CP, %  21.7  21.7  21.7  21.7  21.7  19.7  19.7  19.7  19.7  19.7  20.1  20.1  20.1  20.1  20.1   Total Lys, %  1.51  1.51  1.51  1.51  1.51  1.32  1.32  1.32  1.32  1.32  1.29  1.29  1.29  1.29  1.29   SID6 Lys, %  1.36  1.36  1.36  1.36  1.36  1.21  1.21  1.21  1.21  1.21  1.17  1.17  1.17  1.17  1.17  1Dietary treatments were 1) negative control with no added phytase (NC), 2) NC with 62.5 phytase units (FTU) of phytase/kg of HMC (DM basis) added to HMC and allowed to steep for 24 h before feeding (LS), 3) NC with 125 FTU of phytase/kg of HMC (DM basis) added to HMC and allowed to steep for 24 h before feeding (HS), 4) NC with 62.5 FTU of phytase/kg of HMC (DM basis) added to the base mix and not steeped before feeding (LNS), and 5) NC with 125 FTU of phytase/kg of HMC (DM basis) added to the base mix and not steeped before feeding (HNS). 2Pigs were placed on a 3-phase feeding program with transitions to phase II and III diets occurring from d 7 to 9 and 21 to 23 postweaning, respectively. 3Added phytase given as FTU/kg of HMC on a DM basis [(Ronozyme P (CT) 2500, DSM Nutritional Products Canada Inc., Ayr, Ontario, Canada]. 4Energy and nutrient content of complete diets were estimated based on published energy and nutrient contents of feed ingredients according to NRC (1998), except for HMC (P, 0.33%; Ca, 0.07%) and fish meal (P, 3.88%; Ca, 7.34%), and expressed on an 88% DM basis. 5Based on P availability in ingredients according to NRC (1998) and measured P solubility (assumed to represent availability) in representative samples of stored HMC. For treatments LS and HS, available P also represents increases in P solubility observed during in vitro steeping of HMC with phytase. 6Standardized ileal digestible. View Large The base mixes (Table 1) were mixed, pelleted, and crumbled at the University of Guelph's Arkell Feed Mill. The HMC was stored in a sealed silo at the feed mill until being ground (4.8-mm screen) and transferred in batches of 500 or 1,000 kg to fermentation tanks and mixed with water to achieve a mix of approximately 25% DM. Separate fermentation tanks were dedicated to the preparation and feeding of the HMC with and without phytase, and all HMC was managed in the same manner. For the treatments LS and HS, HMC was steeped with phytase for a minimum of 24 h before feeding. During storage the HMC and water mixtures were agitated for 10 min/h to keep the HMC from settling and to facilitate action of the phytase. Steeped HMC was kept for a maximum of 1 wk before it was disposed of and a new batch prepared. The complete liquid diets (Table 2) were automatically prepared for each pen at each feeding time using a computer controlled liquid feeding system (Big Dutchman HydroJet, Big Dutchman Int., Vechta, Germany). The complete diets were achieved by mixing the appropriate base mix or combination of base mixes, with steeped or unsteeped HMC according to Table 2. The feeding system combined the base mixes, HMC, and water to achieve a DM to water ratio of 1:2.5. The liquid diets were mixed and agitated for 2 min in the feed mixing tank just before feeding. The feed system was programmed to rinse the feed mixing tank and feed lines with water between diet treatments to prevent cross contamination. This rinse water was disposed of in the manure pit. Five pens were assigned to each of the LS, HS, LNS, and HNS treatments, and 4 pens were assigned to the NC treatment according to a randomized block design, with 5 blocks spaced 1 wk apart. The experiment duration was 7 wk postweaning. Feed was offered 6 times per day in equal sized meals starting at 0600 h and at 3-h intervals. The feeding troughs provided 16 cm of feeding space per pig, allowing all pigs to eat simultaneously. Feed delivery to individual pens was computer controlled and involved the use of sensors located 10 mm from the bottom of the troughs (Big Dutchman) that detected if feed was left over from the previous meal. If any feed remained in the trough, the subsequent feeding was skipped. Daily feed allowance was adjusted automatically by the feeding system computer (Big Dutchman) based on a reference feed intake curve (NRC, 1998). However, feed allowance for each pen was manually increased or decreased, relative to the reference feeding curve, to optimize feed intake and to ensure that fresh feed was delivered to each trough at least 4 times daily. Pigs were given free access to water from bowl drinkers throughout the study. Observations and Sampling Pigs were individually weighed and per pen feed usage was determined at weekly intervals for the duration of the study. Pig health and behavior was monitored daily, and any abnormalities were recorded. Pigs that performed poorly, relative to their pen mates, were removed from the study. A minimum of 3 complete diet samples were obtained for each of the diets throughout the study for evaluation of accuracy of feed mixing and determination of nutrient digestibility. Meals representing the actual diet composition as specified at 1, 3, and 7 wk postweaning were mixed by the feeding system and sent to a collecting tank at a valve dedicated to feed sampling, where 2 representative subsamples were taken. Analysis was performed on pooled diet samples. During a 2-d period at the end of wk 7 postweaning, 4 or more random samples of fresh and uncontaminated fecal material were collected from each pen and pooled. Feed and fecal samples were stored at −20°C until subsequent analysis. At the end of the study period, 2 barrows and 2 gilts from each pen with BW closest to the average pen BW were killed by injection of sodium pentobarbital (Euthansol, 340 mg of sodium pentobarbital/mL and 0.3 mL/kg of BW; Schering-Plough Animal Health, Pointe Claire, Québec, Canada) via the intraorbital sinus. Immediately after euthanasia, all internal organs of each pig were removed, and the digestive tract was emptied of all contents. Samples of digesta from the proximal duodenum and distal ileum (1-m segments) were obtained by gentle squeezing immediately after euthanasia and frozen. The bladder was isolated from the killed pigs, and urine samples were obtained via an incision into the bladder and collection of urine into a vial. To prevent nutrient losses, an appropriate amount of HCl was added to urine samples to achieve a pH of less than 2, and samples were then frozen. The front feet were removed at the joint immediately proximal to the metacarpals and frozen individually in plastic bags. The remaining empty body parts (empty carcass, empty viscera) were pooled and frozen until further processing. Sample Processing and Chemical and Statistical Analysis To prepare complete diet and fecal samples for analysis, frozen samples were freeze-dried (Virtis Model 100, SP Scientific, Stone Ridge, NY) and ground through a 1-mm mesh screen. Base mixes, complete diets, and feces were analyzed for DM, OM, CP, P, and Ca (Table 3). Week 7 fecal and ileal digesta samples and phase III complete diets were also analyzed for titanium dioxide content. Pooled frozen empty body parts were ground (Autio Meat Grinder #801, Autio Company, Astoria, OR), and 2 subsamples were taken and immediately frozen for subsequent analysis (Tuitoek et al., 1997). The resulting subsamples were freeze-dried, ground in liquid N to a powder, and analyzed for DM, CP, crude fat, P, and Ca content. The right feet were thawed and the third and fourth metacarpals were removed, manually cleaned of adhering tissue, and refrozen. Both metacarpals were analyzed for DM, P, and Ca content and breaking strength. Duodenal and ileal digesta samples were analyzed for soluble and total P content and ileal digesta samples were analyzed for titanium dioxide content. Urine samples were analyzed for P content. All analysis was performed in duplicate (digesta, urine, feces, carcass, and metacarpal) or triplicate (diet). Table 3. Analyzed nutrient content (adjusted to 88% DM basis) of starter pig base mixes and complete diets1 Item  Phase I2  Phase II2  Phase III2  NC  LNS  HNS  LS  HS  NC  LNS  HNS  LS  HS  NC  LNS  HNS  LS  HS  Base mixes                                            DM, %  90.2  —  91.0  —  —  90.3  —  89.4  —  —  89.3  —  89.1  —  —   CP, %  26.0  —  27.8  —  —  30.6  —  32.2  —  —  32.6  —  34.3  —  —   Total P, %  0.78  —  0.85  —  —  0.57  —  0.52  —  —  0.55  —  0.55  —  —   Ca, %  1.38  —  1.51  —  —  0.87  —  0.95  —  —  1.03  —  1.01  —  —  Complete liquid diets                                           DM, %  22.1  23.3  23.4  21.8  21.3  21.7  23.8  24.7  25.2  23.7  28.7  28.0  28.9  28.0  27.9   CP, %  20.5  19.2  19.8  19.4  21.3  18.9  17.7  18.6  18.3  18.5  17.8  16.4  18.2  18.6  19.5   Total P, %  0.48  0.50  0.52  0.48  0.48  0.38  0.37  0.36  0.38  0.38  0.37  0.37  0.37  0.37  0.37   Soluble P,3 %  0.26  0.30  0.28  0.34  0.34  0.26  0.31  0.35  0.31  0.30  0.20  0.27  0.28  0.25  0.28   Ca,4 %  0.82  0.86  0.89  0.82  0.82  0.44  0.45  0.47  0.44  0.44  0.45  0.45  0.44  0.45  0.45   Ca:P  1.71  1.72  1.71  1.71  1.71  1.16  1.22  1.31  1.16  1.16  1.22  1.22  1.19  1.22  1.22  Item  Phase I2  Phase II2  Phase III2  NC  LNS  HNS  LS  HS  NC  LNS  HNS  LS  HS  NC  LNS  HNS  LS  HS  Base mixes                                            DM, %  90.2  —  91.0  —  —  90.3  —  89.4  —  —  89.3  —  89.1  —  —   CP, %  26.0  —  27.8  —  —  30.6  —  32.2  —  —  32.6  —  34.3  —  —   Total P, %  0.78  —  0.85  —  —  0.57  —  0.52  —  —  0.55  —  0.55  —  —   Ca, %  1.38  —  1.51  —  —  0.87  —  0.95  —  —  1.03  —  1.01  —  —  Complete liquid diets                                           DM, %  22.1  23.3  23.4  21.8  21.3  21.7  23.8  24.7  25.2  23.7  28.7  28.0  28.9  28.0  27.9   CP, %  20.5  19.2  19.8  19.4  21.3  18.9  17.7  18.6  18.3  18.5  17.8  16.4  18.2  18.6  19.5   Total P, %  0.48  0.50  0.52  0.48  0.48  0.38  0.37  0.36  0.38  0.38  0.37  0.37  0.37  0.37  0.37   Soluble P,3 %  0.26  0.30  0.28  0.34  0.34  0.26  0.31  0.35  0.31  0.30  0.20  0.27  0.28  0.25  0.28   Ca,4 %  0.82  0.86  0.89  0.82  0.82  0.44  0.45  0.47  0.44  0.44  0.45  0.45  0.44  0.45  0.45   Ca:P  1.71  1.72  1.71  1.71  1.71  1.16  1.22  1.31  1.16  1.16  1.22  1.22  1.19  1.22  1.22  1Dietary treatments were 1) negative control with no added phytase (NC), 2) NC with 62.5 phytase units (FTU) of phytase/kg of high-moisture corn (HMC; DM basis) added to HMC and allowed to steep for 24 h before feeding (LS), 3) NC with 125 FTU of phytase/kg of HMC (DM basis) added to HMC and allowed to steep for 24 h before feeding (HS), 4) NC with 62.5 FTU of phytase/kg of HMC (DM basis) added to the base mix and not steeped before feeding (LNS), and 5) NC with 125 FTU of phytase/kg of HMC (DM basis) added to the base mix and not steeped before feeding (HNS). Phytase: Ronozyme P (CT) 2500, DSM Nutritional Products Canada Inc., Ayr, Ontario, Canada. 2Pigs were placed on a 3-phase feeding program with transitions to phase II and III diets occurring from d 7 to 9 and 21 to 23 postweaning, respectively. 3Soluble P content in NC was different from all other diets (P = 0.081, 0.074, and 0.004 for phase I, II, and III, respectively; n = 2). 4Based on analyzed content of Ca in base mixes and representative samples of HMC (0.07% Ca, DM basis) and inclusion level of ingredients in the complete diets. View Large Table 3. Analyzed nutrient content (adjusted to 88% DM basis) of starter pig base mixes and complete diets1 Item  Phase I2  Phase II2  Phase III2  NC  LNS  HNS  LS  HS  NC  LNS  HNS  LS  HS  NC  LNS  HNS  LS  HS  Base mixes                                            DM, %  90.2  —  91.0  —  —  90.3  —  89.4  —  —  89.3  —  89.1  —  —   CP, %  26.0  —  27.8  —  —  30.6  —  32.2  —  —  32.6  —  34.3  —  —   Total P, %  0.78  —  0.85  —  —  0.57  —  0.52  —  —  0.55  —  0.55  —  —   Ca, %  1.38  —  1.51  —  —  0.87  —  0.95  —  —  1.03  —  1.01  —  —  Complete liquid diets                                           DM, %  22.1  23.3  23.4  21.8  21.3  21.7  23.8  24.7  25.2  23.7  28.7  28.0  28.9  28.0  27.9   CP, %  20.5  19.2  19.8  19.4  21.3  18.9  17.7  18.6  18.3  18.5  17.8  16.4  18.2  18.6  19.5   Total P, %  0.48  0.50  0.52  0.48  0.48  0.38  0.37  0.36  0.38  0.38  0.37  0.37  0.37  0.37  0.37   Soluble P,3 %  0.26  0.30  0.28  0.34  0.34  0.26  0.31  0.35  0.31  0.30  0.20  0.27  0.28  0.25  0.28   Ca,4 %  0.82  0.86  0.89  0.82  0.82  0.44  0.45  0.47  0.44  0.44  0.45  0.45  0.44  0.45  0.45   Ca:P  1.71  1.72  1.71  1.71  1.71  1.16  1.22  1.31  1.16  1.16  1.22  1.22  1.19  1.22  1.22  Item  Phase I2  Phase II2  Phase III2  NC  LNS  HNS  LS  HS  NC  LNS  HNS  LS  HS  NC  LNS  HNS  LS  HS  Base mixes                                            DM, %  90.2  —  91.0  —  —  90.3  —  89.4  —  —  89.3  —  89.1  —  —   CP, %  26.0  —  27.8  —  —  30.6  —  32.2  —  —  32.6  —  34.3  —  —   Total P, %  0.78  —  0.85  —  —  0.57  —  0.52  —  —  0.55  —  0.55  —  —   Ca, %  1.38  —  1.51  —  —  0.87  —  0.95  —  —  1.03  —  1.01  —  —  Complete liquid diets                                           DM, %  22.1  23.3  23.4  21.8  21.3  21.7  23.8  24.7  25.2  23.7  28.7  28.0  28.9  28.0  27.9   CP, %  20.5  19.2  19.8  19.4  21.3  18.9  17.7  18.6  18.3  18.5  17.8  16.4  18.2  18.6  19.5   Total P, %  0.48  0.50  0.52  0.48  0.48  0.38  0.37  0.36  0.38  0.38  0.37  0.37  0.37  0.37  0.37   Soluble P,3 %  0.26  0.30  0.28  0.34  0.34  0.26  0.31  0.35  0.31  0.30  0.20  0.27  0.28  0.25  0.28   Ca,4 %  0.82  0.86  0.89  0.82  0.82  0.44  0.45  0.47  0.44  0.44  0.45  0.45  0.44  0.45  0.45   Ca:P  1.71  1.72  1.71  1.71  1.71  1.16  1.22  1.31  1.16  1.16  1.22  1.22  1.19  1.22  1.22  1Dietary treatments were 1) negative control with no added phytase (NC), 2) NC with 62.5 phytase units (FTU) of phytase/kg of high-moisture corn (HMC; DM basis) added to HMC and allowed to steep for 24 h before feeding (LS), 3) NC with 125 FTU of phytase/kg of HMC (DM basis) added to HMC and allowed to steep for 24 h before feeding (HS), 4) NC with 62.5 FTU of phytase/kg of HMC (DM basis) added to the base mix and not steeped before feeding (LNS), and 5) NC with 125 FTU of phytase/kg of HMC (DM basis) added to the base mix and not steeped before feeding (HNS). Phytase: Ronozyme P (CT) 2500, DSM Nutritional Products Canada Inc., Ayr, Ontario, Canada. 2Pigs were placed on a 3-phase feeding program with transitions to phase II and III diets occurring from d 7 to 9 and 21 to 23 postweaning, respectively. 3Soluble P content in NC was different from all other diets (P = 0.081, 0.074, and 0.004 for phase I, II, and III, respectively; n = 2). 4Based on analyzed content of Ca in base mixes and representative samples of HMC (0.07% Ca, DM basis) and inclusion level of ingredients in the complete diets. View Large All samples were analyzed for DM content by oven drying at 103°C to a constant weight for a minimum of 24 h (method 950.46B; AOAC, 2003). Nitrogen content in feed, feces, and carcass samples were determined using an automatic analyzer [LECO-FP 428, Leco Instruments Ltd., Mississauga, Ontario, Canada; method 990.03, AOAC (2003)]. Crude protein content was determined by multiplying N content by 6.25. Crude fat content in carcass samples was determined by extraction using a fat analyzer (Ankom XT20, method 2, 01–30–09, Ankom Technology Corp., Macedon, NY). Phosphorus content in feed, feces, carcass, bone, digesta, and urine samples were determined as described by Heinonen and Lahti (1981). Calcium content in feed, feces, carcass, and bone were determined as described by Themelis et al. (2001). Titanium dioxide content in diet, fecal, and ileal digesta samples was analyzed according to Myers et al. (2004). Apparent ileal digestibility and apparent total tract digestibility values for DM, CP, and P were calculated using titanium dioxide as an indigestible marker according to Zhu et al. (2005). Organic matter in feed and feces was determined by subtracting the ash content from the total dry weight for these samples. Metacarpal length was measured at the longest point along the entire bone, and widths were measured at the narrowest and widest points at the midpoint of the shaft (Digital Caliper 06-664-16, Fisher Scientific Company, Ottawa, Ontario, Canada). Breaking strength of bones was determined using a 3-point break test machine (Instron 4204, Instron, Norwood, MA). Force was applied by a load cell to the mid-point of the bone, which was supported at either end by 2 supports placed 3 cm apart. The 50-kN load cell descended onto the bone at a rate of 10 mm/min. Force applied (kg) was monitored by the data sampling program (500 scans/s, Instron LabView, Instron), and the breaking force was determined as the largest recorded force at point of bone failure (Combs et al., 1991; Gentile et al., 2003). Data were subjected to ANOVA based on the mixed model procedure (PROC MIXED, SAS Inst. Inc., Cary, NC). The pen was the experimental unit for all analyses. Block was considered a random effect, and treatment was considered a fixed effect. Initial BW, final carcass plus viscera weight, and bone weight were used as covariables for growth performance, carcass nutrient content and metacarpal characteristics, respectively. Orthogonal contrasts were used to determine the overall response to addition of phytase (LNS, HNS, LS, and HS vs. NC), determine the effect of steeping HMC (LS and HS vs. LNS and HNS), compare the amounts of added phytase (LS and LNS vs. HS and HNS), and assess interaction of added phytase and steeping of HMC. Least squares means were determined for all treatments. When the interactive effect of added phytase and steeping of HMC was significant, treatment means were compared using the Tukey-Kramer test of SAS. Treatment effects and differences between treatment means were considered statistically significant at P ≤ 0.05. A trend toward significance was also considered at P < 0.10. RESULTS AND DISCUSSION In Vitro Release of Phytate P in HMC with Added Phytase All of the quantities of added phytase resulted in release of phytate P in HMC (P < 0.05; Figure 1). There were no differences in the amount of P released among the 3 largest amounts of phytase addition (125, 250, and 500 FTU/kg of DM), all of which showed greater release of P than the 62.5 FTU/kg of DM treatment (P < 0.05). Based on these results, and to observe a dose response to phytase addition, diets for the growth performance study were formulated to contain 62.5 FTU/kg of HMC (DM basis) for treatments LS and LNS and 125 FTU/kg of HMC DM for treatments HS and HNS. Figure 1. View largeDownload slide Effect of graded amounts of added phytase [0, 62.5, 125, 250, and 500 phytase units/kg of DM; Ronozyme P (CT) 2500; DSM Nutritional Products Canada Inc., Ayr, Ontario, Canada] on release of phytate P in a high-moisture corn and water mixture of 1:2 (wt/vol) steeped at 25°C for 32 h. Values represent means of 3 observations ± SE. Figure 1. View largeDownload slide Effect of graded amounts of added phytase [0, 62.5, 125, 250, and 500 phytase units/kg of DM; Ronozyme P (CT) 2500; DSM Nutritional Products Canada Inc., Ayr, Ontario, Canada] on release of phytate P in a high-moisture corn and water mixture of 1:2 (wt/vol) steeped at 25°C for 32 h. Values represent means of 3 observations ± SE. General Observations in Growth Performance Study In total, 34 pigs were removed from study due to BW loss or poor BW gain. There did not seem to be a treatment effect on the number of pigs that were removed. The remaining pigs seemed to be healthy for the duration of the study. Given that published values were used to estimate nutrient contents in most of the feed ingredients, slight differences between formulated and analyzed nutrient content in the base mixes and complete diets were expected (Table 3) and are believed to represent variability in ingredient nutrient content. Mineral analysis tends to have poor repeatability (AAFCO, 1998), especially when analyzing mineral content in complete liquid diets (Columbus et al., 2010). The latter reflects difficulty in proper sampling of liquid feed. Settling of high density feed ingredients, such as limestone, in liquid feed tends to occur quickly, even after vigorous agitation just before sampling. Therefore, the content of Ca in the complete liquid diets were calculated from analyzed contents in HMC and the base mixes, as well as the inclusion of these ingredients in the complete diets. Mineral sources of P were not included in the experimental diets. Therefore, feed ingredient separation was not considered an issue for analyzed P content in the liquid diets. Analyzed titanium dioxide content did not differ between diets in phase III, and so an average value for titanium dioxide content of 0.112% (DM basis) was used for calculating digestibility. Solubilization of P and Nutrient Digestibility The addition of phytase increased the analyzed soluble P content in complete diets, indicating release of phytate P (Table 3; P < 0.01); however, the amount of phytate P release was not affected by steeping or amount of added phytase. Addition of phytase to the NC diet, regardless of amount and steeping, resulted in greater soluble P content as a percentage of total P content in duodenal digesta (P < 0.05; Table 4), which is consistent with treatment effects on soluble P content in the diets and the in vitro observations. These findings indicate that access of phytase to feed during mixing, delivery, and retention in the stomach is sufficient for degradation of phytate, and steeping of HMC with phytase before feeding has little additional effect on phytate P release. Table 4. Effect of phytase [0, 62.5, and 125 phytase units (FTU)/kg of high-moisture corn (HMC; DM basis)] added to the base mix or steeped with HMC on total and soluble P content in digesta sampled from the duodenum, P content in urine, as well as apparent total tract digestibility of DM, OM, CP, P, and Ca in starter pigs fed P-deficient and HMC-based phase III diets1 Item  Treatment  SEM2  Contrast (P-value3)  NC  LNS  HNS  LS  HS  Phytase  Steep  Level  S × L  n4  4  5  5  5  5                 Digesta (slaughter at 7 wk  postweaning)                           Total P, %  0.56  0.61  0.54  0.45  0.55  0.07  0.791  0.234  0.800  0.158   Soluble P, %  0.27  0.34  0.33  0.29  0.33  0.03  0.129  0.271  0.558  0.236   Soluble P, % of total P  49.8  61.7  68.2  62.9  59.7  4.3  0.013  0.352  0.666  0.219  Urine (slaughter at 7 wk  postweaning)                             P, µg/mL  29.7  347  230  205  180  84  0.036  0.211  0.353  0.541  Apparent total tract digestibility  (at wk 7 postweaning)                          DM, %  84.1  82.2  83.8  85.1  84.9  0.7  0.889  0.006  0.300  0.143   OM, %  85.0  83.4  84.7  86.1  85.8  0.7  0.987  0.006  0.392  0.204   CP, %  72.9  69.2  72.8  74.2  76.2  1.1  0.895  0.001  0.012  0.423   P, %  60.9  63.4  67.5  64.4  66.3  2.8  0.159  0.974  0.240  0.662   Ca, %  36.0  39.5  56.5  39.0  41.4  5.6  0.205  0.136  0.067  0.158  Item  Treatment  SEM2  Contrast (P-value3)  NC  LNS  HNS  LS  HS  Phytase  Steep  Level  S × L  n4  4  5  5  5  5                 Digesta (slaughter at 7 wk  postweaning)                           Total P, %  0.56  0.61  0.54  0.45  0.55  0.07  0.791  0.234  0.800  0.158   Soluble P, %  0.27  0.34  0.33  0.29  0.33  0.03  0.129  0.271  0.558  0.236   Soluble P, % of total P  49.8  61.7  68.2  62.9  59.7  4.3  0.013  0.352  0.666  0.219  Urine (slaughter at 7 wk  postweaning)                             P, µg/mL  29.7  347  230  205  180  84  0.036  0.211  0.353  0.541  Apparent total tract digestibility  (at wk 7 postweaning)                          DM, %  84.1  82.2  83.8  85.1  84.9  0.7  0.889  0.006  0.300  0.143   OM, %  85.0  83.4  84.7  86.1  85.8  0.7  0.987  0.006  0.392  0.204   CP, %  72.9  69.2  72.8  74.2  76.2  1.1  0.895  0.001  0.012  0.423   P, %  60.9  63.4  67.5  64.4  66.3  2.8  0.159  0.974  0.240  0.662   Ca, %  36.0  39.5  56.5  39.0  41.4  5.6  0.205  0.136  0.067  0.158  1Dietary treatments were 1) negative control with no added phytase (NC), 2) NC with 62.5 phytase units (FTU) of phytase/kg of HMC (DM basis) added to HMC and allowed to steep for 24 h before feeding (LS), 3) NC with 125 FTU of phytase/kg of HMC (DM basis) added to HMC and allowed to steep for 24 h before feeding (HS), 4) NC with 62.5 FTU of phytase/kg of HMC (DM basis) added to the base mix and not steeped before feeding (LNS), and 5) NC with 125 FTU of phytase/kg of HMC (DM basis) added to the base mix and not steeped before feeding (HNS). Phytase: Ronozyme P (CT) 2500, DSM Nutritional Products Canada Inc., Ayr, Ontario, Canada. 2Reported SEM is largest among measurements. 3Probability of effects of addition of phytase to the NC diet (phytase), steeping of HMC with phytase (steep), level of phytase (level), and interaction of level of added phytase and steeping (S × L). 4Number of pens per treatment. View Large Table 4. Effect of phytase [0, 62.5, and 125 phytase units (FTU)/kg of high-moisture corn (HMC; DM basis)] added to the base mix or steeped with HMC on total and soluble P content in digesta sampled from the duodenum, P content in urine, as well as apparent total tract digestibility of DM, OM, CP, P, and Ca in starter pigs fed P-deficient and HMC-based phase III diets1 Item  Treatment  SEM2  Contrast (P-value3)  NC  LNS  HNS  LS  HS  Phytase  Steep  Level  S × L  n4  4  5  5  5  5                 Digesta (slaughter at 7 wk  postweaning)                           Total P, %  0.56  0.61  0.54  0.45  0.55  0.07  0.791  0.234  0.800  0.158   Soluble P, %  0.27  0.34  0.33  0.29  0.33  0.03  0.129  0.271  0.558  0.236   Soluble P, % of total P  49.8  61.7  68.2  62.9  59.7  4.3  0.013  0.352  0.666  0.219  Urine (slaughter at 7 wk  postweaning)                             P, µg/mL  29.7  347  230  205  180  84  0.036  0.211  0.353  0.541  Apparent total tract digestibility  (at wk 7 postweaning)                          DM, %  84.1  82.2  83.8  85.1  84.9  0.7  0.889  0.006  0.300  0.143   OM, %  85.0  83.4  84.7  86.1  85.8  0.7  0.987  0.006  0.392  0.204   CP, %  72.9  69.2  72.8  74.2  76.2  1.1  0.895  0.001  0.012  0.423   P, %  60.9  63.4  67.5  64.4  66.3  2.8  0.159  0.974  0.240  0.662   Ca, %  36.0  39.5  56.5  39.0  41.4  5.6  0.205  0.136  0.067  0.158  Item  Treatment  SEM2  Contrast (P-value3)  NC  LNS  HNS  LS  HS  Phytase  Steep  Level  S × L  n4  4  5  5  5  5                 Digesta (slaughter at 7 wk  postweaning)                           Total P, %  0.56  0.61  0.54  0.45  0.55  0.07  0.791  0.234  0.800  0.158   Soluble P, %  0.27  0.34  0.33  0.29  0.33  0.03  0.129  0.271  0.558  0.236   Soluble P, % of total P  49.8  61.7  68.2  62.9  59.7  4.3  0.013  0.352  0.666  0.219  Urine (slaughter at 7 wk  postweaning)                             P, µg/mL  29.7  347  230  205  180  84  0.036  0.211  0.353  0.541  Apparent total tract digestibility  (at wk 7 postweaning)                          DM, %  84.1  82.2  83.8  85.1  84.9  0.7  0.889  0.006  0.300  0.143   OM, %  85.0  83.4  84.7  86.1  85.8  0.7  0.987  0.006  0.392  0.204   CP, %  72.9  69.2  72.8  74.2  76.2  1.1  0.895  0.001  0.012  0.423   P, %  60.9  63.4  67.5  64.4  66.3  2.8  0.159  0.974  0.240  0.662   Ca, %  36.0  39.5  56.5  39.0  41.4  5.6  0.205  0.136  0.067  0.158  1Dietary treatments were 1) negative control with no added phytase (NC), 2) NC with 62.5 phytase units (FTU) of phytase/kg of HMC (DM basis) added to HMC and allowed to steep for 24 h before feeding (LS), 3) NC with 125 FTU of phytase/kg of HMC (DM basis) added to HMC and allowed to steep for 24 h before feeding (HS), 4) NC with 62.5 FTU of phytase/kg of HMC (DM basis) added to the base mix and not steeped before feeding (LNS), and 5) NC with 125 FTU of phytase/kg of HMC (DM basis) added to the base mix and not steeped before feeding (HNS). Phytase: Ronozyme P (CT) 2500, DSM Nutritional Products Canada Inc., Ayr, Ontario, Canada. 2Reported SEM is largest among measurements. 3Probability of effects of addition of phytase to the NC diet (phytase), steeping of HMC with phytase (steep), level of phytase (level), and interaction of level of added phytase and steeping (S × L). 4Number of pens per treatment. View Large Based on the observation that phytate P is the main contributor to both insoluble and unavailable P, it can be assumed that P solubility is a reasonable estimate of P availability (Schlemmer et al., 2001; Niven et al., 2007). In stored HMC that has been soaked in water without added phytase, 45% of P is present in a soluble and thus available form (Niven et al., 2007). It can be calculated that HMC contributed 31, 35, and 39% of the total phytate P in phase I, II, and III NC diets, respectively, whereas the remainder was supplied by the base mixes. It has been shown that phytase remains active for at least 2 wk after being added to HMC (Niven et al., 2007). Therefore, further release of phytate P was expected when phytate-containing ingredients were mixed with steeped HMC at time of feeding. This did not seem to be the case in the current study because soluble P content in diets was not influenced by steeping with added phytase. Given that more of the phytate P in this study was present in the base mixes than in HMC, it can be hypothesized that phytase added to the base mixes is more effective in degrading phytate P associated with the base mixes than phytase added to the HMC. This may explain why, in the current study, there was no effect of steeping of HMC with phytase before feeding on P solubilization, and thus P availability. Values for soluble and total P content in ileal digesta and apparent ileal digestibility of P were generated (data not shown), but variation associated with these observations was too large to draw any meaningful conclusions. In this study, sampling ileal digesta at a single time point seemed to be an insufficiently sensitive method for obtaining data on apparent ileal digestibility of P in starter pigs. In future studies, the use of pigs with ileal cannulas would allow for more representative sampling of ileal digesta and may improve measurement of apparent ileal P digestibility. There was no effect of added phytase on apparent total tract digestibility of P (Table 4), which is in contrast to previous studies with starter pigs (Kies et al., 2006; Sands et al., 2009). This discrepancy may reflect differences in methodology and the relatively large variability in P digestibility observed in the current study. It should be noted that P digestibility values reported previously for pigs fed diets without added phytase (Kies et al., 2006; Sands et al., 2009) were substantially less than that for the NC diet in the current study. It is possible that the response to added phytase is reduced at greater P digestibility. In addition, Kies et al. (2006) and Sands et al. (2009) used much larger amounts of added phytase than in the current study, which may have resulted in greater improvements in P digestibility as well. The absence of an effect of added phytase on P digestibility is not consistent with the observed increase in P solubility in duodenal digesta and may reflect the role of P absorption in whole body P homeostasis. It has been shown that pigs reduce P absorption when dietary P exceeds requirements to maintain P homeostasis (Quamme, 1985). However, it has also been demonstrated that P digestibility remains relatively constant over a wide range of dietary P concentrations (Stein et al., 2008). The concept of P digestibility in relation to homeostatic mechanisms requires further exploration. Across treatments added phytase did not affect apparent total tract digestibility of DM, OM, CP, P, and Ca (Table 4). However, steeping of HMC with phytase before feeding resulted in greater apparent total tract digestibility of DM, OM, and CP (P < 0.01) compared with phytase added to the base mix. Moreover, digestibility of CP (P < 0.05) and Ca (P = 0.067) was greater when 125 FTU/kg of HMC DM phytase was added to the diets when compared with diets with 62.5 FTU/kg of HMC DM added phytase. The lack of an overall effect of added phytase is inconsistent with previous studies, in which phytase improved nutrient digestibility in pigs fed conventional dry diets (Kim et al., 2005; Veum et al., 2006) and liquid diets (Columbus et al., 2010). Phytase has been shown to improve the digestibility of protein, carbohydrates, and minerals other than P in starter pigs (Kornegay and Qian, 1996; Han et al., 1997; Brana et al., 2006) and grower-finisher pigs (Johnston et al., 2004; Fan et al., 2005; Kim et al., 2005). Such positive response to phytase can be attributed to the anti-nutritional properties of phytate, and more specifically the binding of nutrients to phytate (Harland and Morris, 1995; Skoglund et al., 1997). The improvement in CP and Ca digestibility when HMC was steeped with increasing amounts of added phytase indicates that further improvements in digestibility of these nutrients can be expected at amounts of phytase supplementation that are greater than 125 FTU/kg of HMC (DM basis). The interactive effects of steeping time and added phytase on nutrient digestibility should be explored further. Urinary P Content Urinary P content was increased considerably with the addition of phytase (P < 0.05; Table 4). Numerically, urinary P content was greatest in pigs fed diets with phytase in the base mix, but likely because of large variability, this effect of steeping vs. nonsteeping was not statistically significant. Pigs fed less than the P requirements will respond by absorbing a greater fraction of their P intake (Quamme, 1985) and increasing renal reabsorption of P to minimize losses (Schroder et al., 1996; Petersen and Stein, 2006). The latter is consistent with observations in the current study because urinary P content was least in pigs fed the diet without added phytase. Based on urinary P content, the available P content seems to be in excess of P requirements in pigs fed diets with added phytase. In future studies, total urinary P excretion should be quantified and used to assess P requirements of pigs in response to feeding graded levels of added phytase. Animal Performance Initial and final BW averaged 6.7 ± 0.1 and 22.0 ± 0.8 kg, respectively, and did not differ among treatments. The addition of phytase, regardless of amount or prior steeping of HMC, resulted in improvements in ADG (45 vs. 53 g/d; SE, 3 g/d; P < 0.05) but had no effect on ADFI or G:F during phase I. There was a trend for greater ADG (183 vs. 153 g/d; SE, 19 g/d; P = 0.094) and ADFI (264 vs. 224 g of DM/d; SE, 21 g of DM/d; P = 0.057) during phase II when phytase was added to base mix when compared with phytase added to HMC. However, over the entire study period, there was no effect of dietary treatment on ADG, ADFI, or G:F (Table 5). Table 5. Effect of phytase [0, 62.5, and 125 phytase units (FTU)/kg of high-moisture corn (HMC; DM basis) added to the base mix or steeped with HMC on overall ADG, ADFI, and G:F of starter pigs fed P-deficient and HMC-based diets during wk 1 to 7 postweaning1 Item  Treatment  SEM2  Contrast (P-value3)  NC  LNS  HNS  LS  HS  Phytase  Steep  Level  S × L  n4  4  5  5  5  5                 ADG, g  305  311  336  308  318  22  0.580  0.577  0.388  0.709  ADFI, g of DM  477  483  526  455  485  28  0.750  0.174  0.167  0.792  G:F, g/g of DM  0.65  0.65  0.64  0.68  0.66  0.02  0.258  0.003  0.226  0.341  Item  Treatment  SEM2  Contrast (P-value3)  NC  LNS  HNS  LS  HS  Phytase  Steep  Level  S × L  n4  4  5  5  5  5                 ADG, g  305  311  336  308  318  22  0.580  0.577  0.388  0.709  ADFI, g of DM  477  483  526  455  485  28  0.750  0.174  0.167  0.792  G:F, g/g of DM  0.65  0.65  0.64  0.68  0.66  0.02  0.258  0.003  0.226  0.341  1Dietary treatments were 1) negative control with no added phytase (NC), 2) NC with 62.5 phytase units (FTU) of phytase/kg of HMC (DM basis) added to HMC and allowed to steep for 24 h before feeding (LS), 3) NC with 125 FTU of phytase/kg of HMC (DM basis) added to HMC and allowed to steep for 24 h before feeding (HS), 4) NC with 62.5 FTU of phytase/kg of HMC (DM basis) added to the base mix and not steeped before feeding (LNS), and 5) NC with 125 FTU of phytase/kg of HMC (DM basis) added to the base mix and not steeped before feeding (HNS). Phytase: Ronozyme P (CT) 2500, DSM Nutritional Products Canada Inc., Ayr, Ontario, Canada. 2Reported SEM is largest among measurements. 3Probability of effects of addition of phytase to the NC diet (phytase), steeping of HMC with phytase (steep), level of phytase (level), and interaction of level of added phytase and steeping (S × L). 4Number of pens per treatment. View Large Table 5. Effect of phytase [0, 62.5, and 125 phytase units (FTU)/kg of high-moisture corn (HMC; DM basis) added to the base mix or steeped with HMC on overall ADG, ADFI, and G:F of starter pigs fed P-deficient and HMC-based diets during wk 1 to 7 postweaning1 Item  Treatment  SEM2  Contrast (P-value3)  NC  LNS  HNS  LS  HS  Phytase  Steep  Level  S × L  n4  4  5  5  5  5                 ADG, g  305  311  336  308  318  22  0.580  0.577  0.388  0.709  ADFI, g of DM  477  483  526  455  485  28  0.750  0.174  0.167  0.792  G:F, g/g of DM  0.65  0.65  0.64  0.68  0.66  0.02  0.258  0.003  0.226  0.341  Item  Treatment  SEM2  Contrast (P-value3)  NC  LNS  HNS  LS  HS  Phytase  Steep  Level  S × L  n4  4  5  5  5  5                 ADG, g  305  311  336  308  318  22  0.580  0.577  0.388  0.709  ADFI, g of DM  477  483  526  455  485  28  0.750  0.174  0.167  0.792  G:F, g/g of DM  0.65  0.65  0.64  0.68  0.66  0.02  0.258  0.003  0.226  0.341  1Dietary treatments were 1) negative control with no added phytase (NC), 2) NC with 62.5 phytase units (FTU) of phytase/kg of HMC (DM basis) added to HMC and allowed to steep for 24 h before feeding (LS), 3) NC with 125 FTU of phytase/kg of HMC (DM basis) added to HMC and allowed to steep for 24 h before feeding (HS), 4) NC with 62.5 FTU of phytase/kg of HMC (DM basis) added to the base mix and not steeped before feeding (LNS), and 5) NC with 125 FTU of phytase/kg of HMC (DM basis) added to the base mix and not steeped before feeding (HNS). Phytase: Ronozyme P (CT) 2500, DSM Nutritional Products Canada Inc., Ayr, Ontario, Canada. 2Reported SEM is largest among measurements. 3Probability of effects of addition of phytase to the NC diet (phytase), steeping of HMC with phytase (steep), level of phytase (level), and interaction of level of added phytase and steeping (S × L). 4Number of pens per treatment. View Large Average daily gain in the current study was slightly less than expected based on previous studies (Brana et al., 2006; Veum et al., 2006). This is most likely due to liquid feeding management practices and the lack of growth-promoting feed additives in the diets fed in the current study. One of the main concerns with liquid feeding starter pigs is balancing freshness of liquid feed in the trough with maximizing intake. Uneaten liquid feed may quickly spoil and become unpalatable to the pigs, reducing intake (Brooks et al., 2001). In the current study, sensor feeding was used to avoid spoilage of uneaten feed, which likely resulted in some degree of feed intake restriction. Therefore, the somewhat smaller ADG observed in this study is thought to be a reflection of reduced feed intake and not dietary treatment. In previous studies, a positive growth performance response to added dietary phytase has been observed in starter pigs that were fed P-deficient diets (Brana et al., 2006; Kies et al., 2006; Veum et al., 2006). However, other studies have shown no response to added phytase or a response only in very young pigs (Omogbenigun et al., 2003; Kim et al., 2005; Yang and Baidoo, 2005). The growth performance response to added phytase has been shown to decline with increasing dietary content of available P (Yi et al., 1996) and increasing amounts of added phytase (Kornegay and Qian, 1996). This may explain why in some studies no response to added phytase was observed in starter pigs. Also, given the small amounts of added phytase in the current study, the lack of response can be attributed largely to the available P content in the NC diets. In the current study, diets did not contain any sources of inorganic P and total P content in the complete diets was substantially less (25 to 35%) than requirements for total P (NRC, 1998). However, based on the soluble P content of the diets, the available P content in the phase III NC diets was estimated to be only 9% less than available P requirements for starter pigs, according to NRC (1998). Apparently, the degree of P intake restriction required to induce a growth performance response to added phytase cannot be achieved in HMC-based starter pig diets. Indeed, ingredients that are typically added to phase I and II starter pig diets such as wheat, fish meal, blood plasma, and whey all have a relatively large content of total and available P (NRC, 1998) and would, therefore, reduce the need for supplemental inorganic P. In addition, wheat has been shown to have intrinsic phytase activity (Shen et al., 2005), which may have contributed to a greater available P content in all the diets. Therefore, despite efforts to restrict P intake in the current study, dietary available P content appeared adequate for maximizing growth performance of starter pigs that are liquid-fed HMC-based diets. These observations provide further support that pig diets should be formulated based on available P content. Empty Body Composition Among pigs that were used for evaluation of body mineral content and bone characteristics, there was a tendency for greater BW at slaughter (P = 0.067; Table 6) of pigs fed phytase-containing diets when compared with the NC. Pigs receiving the largest amount of added phytase had the heaviest BW at slaughter (P < 0.05). There were minor but statistically significant effects of steeping HMC with phytase on weights of the empty carcass and empty viscera (P < 0.05), with steeping of HMC before feeding resulting in decreased carcass weight and greater empty viscera weight. There was no impact of dietary treatment on carcass dressing percent or content of DM and crude fat in the empty body. Addition of phytase to the NC diet resulted in greater empty body content and mass of P and Ca (P < 0.001), with the greatest empty body P and Ca mass at the largest amount of added phytase (P < 0.05). Empty body CP mass was also greatest at the largest amount of added phytase (P < 0.05), illustrating the positive relationship between whole body protein retention and whole body mineral retention (Weis et al., 2004; Schinckel et al., 2008). Table 6. Effect of phytase [0, 62.5, and 125 phytase units (FTU)/kg of high-moisture corn (HMC; DM basis)] added to the base mix or steeped with HMC on physical characteristics and CP, crude fat, and P content (DM basis) of the empty body (empty carcass, empty viscera) in pigs fed P-deficient and HMC-based diets1 Item  Treatment  SEM2  Contrast (P-value3)  NC  LNS  HNS  LS  HS  Phytase  Steep  Level  S × L  n4  4  5  5  5  5                 BW, kg  23.0  23.2  23.4  23.0  23.3  0.1  0.067  0.293  0.049  0.405  Empty carcass, kg  16.48  16.49  16.50  16.42  16.41  0.03  0.598  0.024  0.968  0.717  Empty viscera, kg  3.58  3.56  3.55  3.63  3.65  0.03  0.598  0.024  0.968  0.717  Empty body, kg  19.5  20.1  21.0  18.8  20.4  0.8  0.568  0.215  0.107  0.670  Carcass dressing, %  71.6  71.0  70.4  71.3  70.2  0.4  0.072  0.915  0.082  0.518  DM, %  34.8  35.1  34.8  34.5  34.6  0.4  0.935  0.185  0.772  0.511  CP, %  49.9  48.1  49.9  50.7  50.0  0.8  0.812  0.106  0.499  0.094  CP, kg  3.32  3.18  3.37  3.14  3.32  0.07  0.389  0.469  0.015  0.874  Crude fat, %  42.5  42.4  40.8  40.9  41.5  0.9  0.257  0.644  0.576  0.194  Crude fat, kg  2.84  2.81  2.78  2.56  2.78  0.10  0.347  0.183  0.345  0.186  P, %  1.31  1.52  1.58  1.56  1.58  0.05  <0.001  0.699  0.480  0.650  P, g  88.5  100.7  106.4  96.2  104.2  3.3  0.003  0.289  0.048  0.704  Ca, %  1.85  2.35  2.47  2.41  2.48  0.11  <0.001  0.693  0.353  0.811  Ca, g  125.3  154.9  166.0  147.4  164.1  7.4  0.001  0.504  0.071  0.676  Item  Treatment  SEM2  Contrast (P-value3)  NC  LNS  HNS  LS  HS  Phytase  Steep  Level  S × L  n4  4  5  5  5  5                 BW, kg  23.0  23.2  23.4  23.0  23.3  0.1  0.067  0.293  0.049  0.405  Empty carcass, kg  16.48  16.49  16.50  16.42  16.41  0.03  0.598  0.024  0.968  0.717  Empty viscera, kg  3.58  3.56  3.55  3.63  3.65  0.03  0.598  0.024  0.968  0.717  Empty body, kg  19.5  20.1  21.0  18.8  20.4  0.8  0.568  0.215  0.107  0.670  Carcass dressing, %  71.6  71.0  70.4  71.3  70.2  0.4  0.072  0.915  0.082  0.518  DM, %  34.8  35.1  34.8  34.5  34.6  0.4  0.935  0.185  0.772  0.511  CP, %  49.9  48.1  49.9  50.7  50.0  0.8  0.812  0.106  0.499  0.094  CP, kg  3.32  3.18  3.37  3.14  3.32  0.07  0.389  0.469  0.015  0.874  Crude fat, %  42.5  42.4  40.8  40.9  41.5  0.9  0.257  0.644  0.576  0.194  Crude fat, kg  2.84  2.81  2.78  2.56  2.78  0.10  0.347  0.183  0.345  0.186  P, %  1.31  1.52  1.58  1.56  1.58  0.05  <0.001  0.699  0.480  0.650  P, g  88.5  100.7  106.4  96.2  104.2  3.3  0.003  0.289  0.048  0.704  Ca, %  1.85  2.35  2.47  2.41  2.48  0.11  <0.001  0.693  0.353  0.811  Ca, g  125.3  154.9  166.0  147.4  164.1  7.4  0.001  0.504  0.071  0.676  1Dietary treatments were 1) negative control with no added phytase (NC), 2) NC with 62.5 phytase units (FTU) of phytase/kg of HMC (DM basis) added to HMC and allowed to steep for 24 h before feeding (LS), 3) NC with 125 FTU of phytase/kg of HMC (DM basis) added to HMC and allowed to steep for 24 h before feeding (HS), 4) NC with 62.5 FTU of phytase/kg of HMC (DM basis) added to the base mix and not steeped before feeding (LNS), and 5) NC with 125 FTU of phytase/kg of HMC (DM basis) added to the base mix and not steeped before feeding (HNS). Phytase: Ronozyme P (CT) 2500, DSM Nutritional Products Canada Inc., Ayr, Ontario, Canada. 2Reported SEM is largest among measurements. 3Probability of effects of addition of phytase to the NC diet (phytase), steeping of HMC with phytase (steep), level of phytase (level), and interaction of level of added phytase and steeping (S × L). 4Number of pens per treatment. View Large Table 6. Effect of phytase [0, 62.5, and 125 phytase units (FTU)/kg of high-moisture corn (HMC; DM basis)] added to the base mix or steeped with HMC on physical characteristics and CP, crude fat, and P content (DM basis) of the empty body (empty carcass, empty viscera) in pigs fed P-deficient and HMC-based diets1 Item  Treatment  SEM2  Contrast (P-value3)  NC  LNS  HNS  LS  HS  Phytase  Steep  Level  S × L  n4  4  5  5  5  5                 BW, kg  23.0  23.2  23.4  23.0  23.3  0.1  0.067  0.293  0.049  0.405  Empty carcass, kg  16.48  16.49  16.50  16.42  16.41  0.03  0.598  0.024  0.968  0.717  Empty viscera, kg  3.58  3.56  3.55  3.63  3.65  0.03  0.598  0.024  0.968  0.717  Empty body, kg  19.5  20.1  21.0  18.8  20.4  0.8  0.568  0.215  0.107  0.670  Carcass dressing, %  71.6  71.0  70.4  71.3  70.2  0.4  0.072  0.915  0.082  0.518  DM, %  34.8  35.1  34.8  34.5  34.6  0.4  0.935  0.185  0.772  0.511  CP, %  49.9  48.1  49.9  50.7  50.0  0.8  0.812  0.106  0.499  0.094  CP, kg  3.32  3.18  3.37  3.14  3.32  0.07  0.389  0.469  0.015  0.874  Crude fat, %  42.5  42.4  40.8  40.9  41.5  0.9  0.257  0.644  0.576  0.194  Crude fat, kg  2.84  2.81  2.78  2.56  2.78  0.10  0.347  0.183  0.345  0.186  P, %  1.31  1.52  1.58  1.56  1.58  0.05  <0.001  0.699  0.480  0.650  P, g  88.5  100.7  106.4  96.2  104.2  3.3  0.003  0.289  0.048  0.704  Ca, %  1.85  2.35  2.47  2.41  2.48  0.11  <0.001  0.693  0.353  0.811  Ca, g  125.3  154.9  166.0  147.4  164.1  7.4  0.001  0.504  0.071  0.676  Item  Treatment  SEM2  Contrast (P-value3)  NC  LNS  HNS  LS  HS  Phytase  Steep  Level  S × L  n4  4  5  5  5  5                 BW, kg  23.0  23.2  23.4  23.0  23.3  0.1  0.067  0.293  0.049  0.405  Empty carcass, kg  16.48  16.49  16.50  16.42  16.41  0.03  0.598  0.024  0.968  0.717  Empty viscera, kg  3.58  3.56  3.55  3.63  3.65  0.03  0.598  0.024  0.968  0.717  Empty body, kg  19.5  20.1  21.0  18.8  20.4  0.8  0.568  0.215  0.107  0.670  Carcass dressing, %  71.6  71.0  70.4  71.3  70.2  0.4  0.072  0.915  0.082  0.518  DM, %  34.8  35.1  34.8  34.5  34.6  0.4  0.935  0.185  0.772  0.511  CP, %  49.9  48.1  49.9  50.7  50.0  0.8  0.812  0.106  0.499  0.094  CP, kg  3.32  3.18  3.37  3.14  3.32  0.07  0.389  0.469  0.015  0.874  Crude fat, %  42.5  42.4  40.8  40.9  41.5  0.9  0.257  0.644  0.576  0.194  Crude fat, kg  2.84  2.81  2.78  2.56  2.78  0.10  0.347  0.183  0.345  0.186  P, %  1.31  1.52  1.58  1.56  1.58  0.05  <0.001  0.699  0.480  0.650  P, g  88.5  100.7  106.4  96.2  104.2  3.3  0.003  0.289  0.048  0.704  Ca, %  1.85  2.35  2.47  2.41  2.48  0.11  <0.001  0.693  0.353  0.811  Ca, g  125.3  154.9  166.0  147.4  164.1  7.4  0.001  0.504  0.071  0.676  1Dietary treatments were 1) negative control with no added phytase (NC), 2) NC with 62.5 phytase units (FTU) of phytase/kg of HMC (DM basis) added to HMC and allowed to steep for 24 h before feeding (LS), 3) NC with 125 FTU of phytase/kg of HMC (DM basis) added to HMC and allowed to steep for 24 h before feeding (HS), 4) NC with 62.5 FTU of phytase/kg of HMC (DM basis) added to the base mix and not steeped before feeding (LNS), and 5) NC with 125 FTU of phytase/kg of HMC (DM basis) added to the base mix and not steeped before feeding (HNS). Phytase: Ronozyme P (CT) 2500, DSM Nutritional Products Canada Inc., Ayr, Ontario, Canada. 2Reported SEM is largest among measurements. 3Probability of effects of addition of phytase to the NC diet (phytase), steeping of HMC with phytase (steep), level of phytase (level), and interaction of level of added phytase and steeping (S × L). 4Number of pens per treatment. View Large The heavier BW observed in pigs fed diets containing 125 FTU/kg is most likely due to gut fill because this treatment effect was not evident in empty BW. The observed increase in whole empty body content and mass of both P and Ca with the addition of phytase to the diets is consistent with previous observations (Fan et al., 2005; Emiola et al., 2009) and the observed increases in soluble P content in the liquid diets and duodenal digesta in the current study. However, whole body Ca and P retention rates at the largest amount of added phytase are inconsistent with the lack of treatment effects on P digestibility and treatment effects on urinary P content. In the current study, measures of body P content had less variability than measures of P digestibility and urinary P content, indicating that measures of body P content provided a more informative response to dietary treatments than P digestibility and urinary P content. The current findings support previous observations that a greater available P intake is required for maximum P retention than for maximum growth performance (NRC, 1998; Fan et al., 2005; Emiola et al., 2009). In addition, these findings provide further evidence that regulation of P absorption and urinary P excretion are important aspects of P homeostasis and whole body mineral retention. Metacarpal Characteristics Overall, there was no treatment effect on metacarpal dimension, except for a trend toward an increase in the dry weight of metacarpals with the addition of phytase to the diets (P = 0.075; Table 7). Added phytase increased metacarpal content of DM and P (P < 0.05) and tended to increase content of Ca (P = 0.065). There was an interactive effect between amount of phytase and steeping observed for P content of metacarpals (P < 0.05). Metacarpal P content was greatest for HNS when compared with treatments NC, LNS, and HS, with the LS treatment being intermediate and not different from any other treatment. Metacarpal breaking strength was greatest in pigs fed diets with the greatest phytase content (P < 0.05). Table 7. Effect of phytase [0, 62.5, and 125 phytase units (FTU)/kg of high-moisture corn (HMC; DM basis) added to the base mix or steeped with HMC on physical characteristics and content of P and Ca (DM basis) of third and fourth metacarpals from pigs fed P-deficient and HMC-based diets1 Item  Treatment  SEM2  Contrast (P-value3)  NC  LNS  HNS  LS  HS  Phytase  Steep  Level  S × L  n4  4  5  5  5  5                 Length, mm  49.2  49.6  50.4  48.7  49.6  0.5  0.530  0.090  0.086  0.949  W-1,5 mm  10.6  10.8  10.8  10.3  10.6  0.2  0.929  0.071  0.425  0.407  W-2,5 mm  13.6  14.0  14.0  13.6  13.9  0.2  0.243  0.291  0.559  0.504  Wet wt, g  8.77  9.14  9.48  9.65  9.06  0.23  0.197  0.035  0.076  0.857  Dry wt, g  4.64  4.99  5.17  4.68  4.99  0.16  0.075  0.105  0.105  0.628  DM, %  53.0  54.6  54.5  54.1  55.0  0.6  0.011  0.931  0.381  0.291  P, % of bone  5.40a  5.51a  6.02b  5.64ab  5.55a  0.12  0.030  0.071  0.029  0.007  P, g/bone  0.27a  0.27a  0.30b  0.28ab  0.27a  0.01  0.042  0.061  0.026  0.005  Ca, % of bone  11.4  11.7  12.6  11.9  12.0  0.3  0.065  0.332  0.067  0.093  Ca, g/bone  0.56  0.58  0.62  0.58  0.59  0.01  0.063  0.231  0.058  0.075  Strength, kg  32.0  30.8  34.0  30.1  31.8  1.3  0.874  0.107  0.022  0.618  Item  Treatment  SEM2  Contrast (P-value3)  NC  LNS  HNS  LS  HS  Phytase  Steep  Level  S × L  n4  4  5  5  5  5                 Length, mm  49.2  49.6  50.4  48.7  49.6  0.5  0.530  0.090  0.086  0.949  W-1,5 mm  10.6  10.8  10.8  10.3  10.6  0.2  0.929  0.071  0.425  0.407  W-2,5 mm  13.6  14.0  14.0  13.6  13.9  0.2  0.243  0.291  0.559  0.504  Wet wt, g  8.77  9.14  9.48  9.65  9.06  0.23  0.197  0.035  0.076  0.857  Dry wt, g  4.64  4.99  5.17  4.68  4.99  0.16  0.075  0.105  0.105  0.628  DM, %  53.0  54.6  54.5  54.1  55.0  0.6  0.011  0.931  0.381  0.291  P, % of bone  5.40a  5.51a  6.02b  5.64ab  5.55a  0.12  0.030  0.071  0.029  0.007  P, g/bone  0.27a  0.27a  0.30b  0.28ab  0.27a  0.01  0.042  0.061  0.026  0.005  Ca, % of bone  11.4  11.7  12.6  11.9  12.0  0.3  0.065  0.332  0.067  0.093  Ca, g/bone  0.56  0.58  0.62  0.58  0.59  0.01  0.063  0.231  0.058  0.075  Strength, kg  32.0  30.8  34.0  30.1  31.8  1.3  0.874  0.107  0.022  0.618  a,bWithin a row, means without a common superscript differ (P < 0.05). 1Dietary treatments were 1) negative control with no added phytase (NC), 2) NC with 62.5 phytase units (FTU) of phytase/kg of HMC (DM basis) added to HMC and allowed to steep for 24 h before feeding (LS), 3) NC with 125 FTU of phytase/kg of HMC (DM basis) added to HMC and allowed to steep for 24 h before feeding (HS), 4) NC with 62.5 FTU of phytase/kg of HMC (DM basis) added to the base mix and not steeped before feeding (LNS), and 5) NC with 125 FTU of phytase/kg of HMC (DM basis) added to the base mix and not steeped before feeding (HNS). Phytase: Ronozyme P (CT) 2500, DSM Nutritional Products Canada Inc., Ayr, Ontario, Canada. 2Reported SEM is largest among measurements. 3Probability of effects of addition of phytase to the NC diet (phytase), steeping of HMC with phytase (steep), level of phytase (level), and interaction of level of added phytase and steeping (S × L). Where S × L was found to be significant, a multiple comparison test (Tukey-Kramer) was performed to determine treatment differences. 4Number of pens per treatment. 5Metacarpals were measured at the narrowest (W-1) and widest (W-2) point at the mid-point of the shaft. View Large Table 7. Effect of phytase [0, 62.5, and 125 phytase units (FTU)/kg of high-moisture corn (HMC; DM basis) added to the base mix or steeped with HMC on physical characteristics and content of P and Ca (DM basis) of third and fourth metacarpals from pigs fed P-deficient and HMC-based diets1 Item  Treatment  SEM2  Contrast (P-value3)  NC  LNS  HNS  LS  HS  Phytase  Steep  Level  S × L  n4  4  5  5  5  5                 Length, mm  49.2  49.6  50.4  48.7  49.6  0.5  0.530  0.090  0.086  0.949  W-1,5 mm  10.6  10.8  10.8  10.3  10.6  0.2  0.929  0.071  0.425  0.407  W-2,5 mm  13.6  14.0  14.0  13.6  13.9  0.2  0.243  0.291  0.559  0.504  Wet wt, g  8.77  9.14  9.48  9.65  9.06  0.23  0.197  0.035  0.076  0.857  Dry wt, g  4.64  4.99  5.17  4.68  4.99  0.16  0.075  0.105  0.105  0.628  DM, %  53.0  54.6  54.5  54.1  55.0  0.6  0.011  0.931  0.381  0.291  P, % of bone  5.40a  5.51a  6.02b  5.64ab  5.55a  0.12  0.030  0.071  0.029  0.007  P, g/bone  0.27a  0.27a  0.30b  0.28ab  0.27a  0.01  0.042  0.061  0.026  0.005  Ca, % of bone  11.4  11.7  12.6  11.9  12.0  0.3  0.065  0.332  0.067  0.093  Ca, g/bone  0.56  0.58  0.62  0.58  0.59  0.01  0.063  0.231  0.058  0.075  Strength, kg  32.0  30.8  34.0  30.1  31.8  1.3  0.874  0.107  0.022  0.618  Item  Treatment  SEM2  Contrast (P-value3)  NC  LNS  HNS  LS  HS  Phytase  Steep  Level  S × L  n4  4  5  5  5  5                 Length, mm  49.2  49.6  50.4  48.7  49.6  0.5  0.530  0.090  0.086  0.949  W-1,5 mm  10.6  10.8  10.8  10.3  10.6  0.2  0.929  0.071  0.425  0.407  W-2,5 mm  13.6  14.0  14.0  13.6  13.9  0.2  0.243  0.291  0.559  0.504  Wet wt, g  8.77  9.14  9.48  9.65  9.06  0.23  0.197  0.035  0.076  0.857  Dry wt, g  4.64  4.99  5.17  4.68  4.99  0.16  0.075  0.105  0.105  0.628  DM, %  53.0  54.6  54.5  54.1  55.0  0.6  0.011  0.931  0.381  0.291  P, % of bone  5.40a  5.51a  6.02b  5.64ab  5.55a  0.12  0.030  0.071  0.029  0.007  P, g/bone  0.27a  0.27a  0.30b  0.28ab  0.27a  0.01  0.042  0.061  0.026  0.005  Ca, % of bone  11.4  11.7  12.6  11.9  12.0  0.3  0.065  0.332  0.067  0.093  Ca, g/bone  0.56  0.58  0.62  0.58  0.59  0.01  0.063  0.231  0.058  0.075  Strength, kg  32.0  30.8  34.0  30.1  31.8  1.3  0.874  0.107  0.022  0.618  a,bWithin a row, means without a common superscript differ (P < 0.05). 1Dietary treatments were 1) negative control with no added phytase (NC), 2) NC with 62.5 phytase units (FTU) of phytase/kg of HMC (DM basis) added to HMC and allowed to steep for 24 h before feeding (LS), 3) NC with 125 FTU of phytase/kg of HMC (DM basis) added to HMC and allowed to steep for 24 h before feeding (HS), 4) NC with 62.5 FTU of phytase/kg of HMC (DM basis) added to the base mix and not steeped before feeding (LNS), and 5) NC with 125 FTU of phytase/kg of HMC (DM basis) added to the base mix and not steeped before feeding (HNS). Phytase: Ronozyme P (CT) 2500, DSM Nutritional Products Canada Inc., Ayr, Ontario, Canada. 2Reported SEM is largest among measurements. 3Probability of effects of addition of phytase to the NC diet (phytase), steeping of HMC with phytase (steep), level of phytase (level), and interaction of level of added phytase and steeping (S × L). Where S × L was found to be significant, a multiple comparison test (Tukey-Kramer) was performed to determine treatment differences. 4Number of pens per treatment. 5Metacarpals were measured at the narrowest (W-1) and widest (W-2) point at the mid-point of the shaft. View Large The effect of added phytase on bone mineral content and breaking strength are in agreement with previous studies (Kornegay and Qian, 1996; Yi et al., 1996; Omogbenigun et al., 2003; Brana et al., 2006). Improvements in bone strength in response to added phytase have been observed in the absence of improvements in ADG (Kornegay and Qian, 1996; Brana et al., 2006). In the pig, P utilization for soft tissue growth is prioritized over P for skeletal growth (Crenshaw, 2001). Therefore, inadequate dietary P supply or improvements in P availability would be more apparent in skeletal measures of P retention than measures of pig performance (Yi et al., 1996; Zhang et al., 2000). The results of the current study indicate that greater dietary available P contents are required for maximum skeletal development. Furthermore, the presence of an interactive effect between phytase activity and steeping suggests that a high level of phytase without steeping or a low level of phytase with steeping achieve similar results with regards to P retention in pigs, and that steeping may only provide benefits if a low level of phytase is used. In summary, based on measures of whole body P retention, P content of metacarpals, and metacarpal breaking strength, P availability and utilization was improved with the addition of 62.5 or 125 FTU/kg of phytase to HMC-based liquid starter pig diets. The absence of a growth performance response to added phytase supports previous findings that greater amounts of available P intake are required for maximum P retention than for maximum growth performance. Other responses that were evaluated, including ileal and fecal P digestibility, urinary P content and bone breaking strength appeared rather variable and somewhat inconsistent across treatments. Most of the responses to both amounts of phytase were similar and indicate greater efficacy of phytase in liquid diets than in dry diets. In general, steeping of HMC with phytase for more than 24 h provided little benefit when compared with adding phytase with dry feed ingredients to the liquid diet just before feeding. 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Sci.  83: 1044– 1053. https://doi.org/15827249 Google Scholar CrossRef Search ADS PubMed  Footnotes 1 Financial support was provided by Ontario Pork (Guelph, Ontario, Canada), Natural Sciences and Engineering Research Council of Canada (Ottawa, Ontario, Canada), Ontario Ministry of Agriculture, Food, and Rural Affairs (Guelph, Ontario, Canada), and industrial partners of the Swine Liquid Feeding: Big Dutchman Int. (Vechta, Germany), Daco Laboratories Inc. (Stratford, Ontario, Canada), Grand Valley Fortifiers (Cambridge, Ontario, Canada), BSC Animal Nutrition (St. Marys, Ontario, Canada), Great Lakes Nutrition (Monkton, Ontario, Canada), Furst McNess (Freeport, IL), Chris Hansen Laboratories (Milwaukee, WI), Kenpal Farm Products Inc. (Centralia, Ontario, Canada), Dwyer Manufacturing Ltd. (Dublin, Ontario, Canada), Farmix/Ridley Inc. (Mitchell, Ontario, Canada), and Corn Products International (Westchester, IL). Technical assistance provided by M. Quinton, M. Hansel, L. Trouten-Radford, G. VanderVoort, and staff at the University of Guelph's Arkell Swine Research Station is greatly appreciated. American Society of Animal Science
TI - Phosphorus utilization in starter pigs fed high-moisture corn-based liquid diets steeped with phytase
JF - Journal of Animal Science
DO - 10.2527/jas.2010-3011
DA - 2010-12-01
UR - https://www.deepdyve.com/lp/oxford-university-press/phosphorus-utilization-in-starter-pigs-fed-high-moisture-corn-based-ZUbzZDZlr4
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EP - 3976
VL - 88
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DP - DeepDyve
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