Efficacy of an E. coli phytase expressed in yeast for releasing phytate-bound phosphorus in young chicks and pigs

Four chick trials and one pig trial were conducted to investigate the phosphorus-releasing efficacy oftwo commercial phytase enzymes (Natuphos and Ronozyme) and an experimental E. coli phytase enzyme (ECP) when added to corn-soybean meal diets containing no supplemental inorganic P (iP). In the 13- or 14-d chick trials, three or four graded levels of iP (0, 0.05,0.10,0.15%) from KH2PO4 were added to the basal diet to construct standard curves from which bioavailable P release could be calculated for the phytase treatments. In all cases, phytase supplementation levels were based on an assessment of phytase premix activity (i.e., P release from Na phytate at pH 5.5). Linear (P < 0.01) responses in tibia ash and weight gain resulted from iP supplementation in all assays. In the first chick trial, supplementation of 500 phytase units (FTU)/kg of ECP resulted in superior (P < 0.01) weight gain and tibia ash values compared with 500 FTU/kg of Natuphos. Results of the second chick trial revealed P-release values of 0.032 and 0.028% for 500 FTU/kg Natuphos and Ronozyme, respectively, and these were lower (P < 0.01) than the 0.125% P-release value for 500 FTU/kg of ECP. Tibia ash responded quadratically (P < 0.05) in response to graded levels of ECP up to 1,500 FTU/kg in the third chick trial. Combining Natuphos with either Ronozyme or ECP in Chick Trial 4 revealed no synergism between phytases with different initiation sites of P removal. The pig trial involved 10 individually fed weanling pigs per diet, and and phytase enzymes were supplemented to provide 400 FTU/kg in diets containing 0.60% Ca. Based on the linear regression of fibula ash on supplemental iP intake (r2 = 0.87), P-release values were 0.081% for Natuphos, 0.043% for Ronozyme, and 0.108% for ECP. These trials revealed an advantage of the E. coli phytase over the commercial phytases in young chicks.     

Consequences of calcium interactions with phytate and phytase for poultry and pigs

Despite increasing practical experience and cascades of scientific reports on exogenous microbial phytases, several issues associated with their use remain unresolved because of the ambiguous and, at times, conflicting data that has been generated. One possible cause of these inconsistent outcomes is dietary calcium (Ca) levels, which are mainly derived from limestone. Thus the purpose of this review is to examine Ca interactions with dietary phytate and phytases, particularly exogenous, microbial phytases, and their consequences for poultry and pigs. The polyanionic phytate molecule has a tremendous capacity to chelate cations and form insoluble Ca–phytate complexes, which are refractory to phytase activity. Thus Ca–phytate complex formation along the gastrointestinal tract, where one phytate (IP₆) molecule binds up to five Ca atoms, assumes importance and approximately one third of dietary Ca may be bound to phytate in digesta. Consequently, phytate limits the availability of both P and Ca as a result of insoluble Ca–phytate complex formation, the extent of which is driven by gut pH and molar ratios of the two components. It is accepted that Ca–phytate complexes are mainly formed in the small intestine where they have a substantial negative influence on the efficacy of mucosal phytase. However, exogenous phytases are mainly active in more proximal segments of the gut and lower pH levels, so their efficacy should not be influenced by Ca–phytate complexes in the small intestine. There is, however, data to indicate that Ca and phytate interactions occur under acidic conditions with the formation of soluble and insoluble Ca–phytate species, which could negatively impact on exogenous phytase efficacy. Also, Ca will tend to elevate gut pH because of limestone's very high acid binding capacity, which will favour Ca–phytate interactions and may influence the activity of exogenous phytases depending on their pH activity spectrum. The de novo formation of binary protein–phytate complexes that are refractory to pepsin hydrolysis may be fundamental to the negative impact of phytate on the digestibility of protein/amino acids. However, high dietary Ca levels may disrupt protein–phytate complex formation by interacting with both phytate and protein even at acidic pH levels, thereby influencing the outcomes of phytase amino acid digestibility assays. Finally, it is increasingly necessary to define the Ca and nonphytate-P requirements of pigs and poultry offered phytase-supplemented diets.     

Efficacy and equivalency of an Escherichia coli-derived phytase for replacing inorganic phosphorus in the diets of broiler chickens and young pigs

Two studies were conducted to determine the efficacy of an Escherichia coli-derived phytase (ECP) and its equivalency relative to inorganic phosphorus (iP) from monosodium phosphate (MSP). In Exp. 1, one thousand two hundred 1-d-old male broilers were used in a 42-d trial to assess the effect of ECP and iP supplementation on growth performance and nutrient digestibility. Dietary treatments were based on corn-soybean meal basal diets (BD) containing 239 and 221 g of CP, 8.2 and 6.6 g of Ca, and 2.4 and 1.5 g of nonphytate P (nPP) per kg for the starter and grower phases, respectively. Treatments consisted of the BD; the BD + 0.6, 1.2, or 1.8 g of iP from MSP per kg; and the BD + 250, 500, 750, or 1,000 phytase units (FTU) of ECP per kg. Increasing levels of MSP improved gain, gain:feed, and tibia ash (linear, P < 0.01). Increasing levels of ECP improved gain, gain:feed, tibia ash (linear, P < 0.01), apparent ileal digestibility of P, N, Arg, His, Phe, and Trp at d 21 (linear, P < 0.05), and apparent retention of P at d 21 (linear, P < 0.05). Increasing levels of ECP decreased apparent retention of energy (linear, P < 0.01). Five hundred FTU of ECP per kg was determined to be equivalent to the addition of 0.72, 0.78, and 1.19 g of iP from MSP per kg in broiler diets based on gain, feed intake, and bone ash, respectively. In Exp. 2, forty-eight 10-kg pigs were used in a 28-d trial to assess the effect of ECP and iP supplementation on growth performance and nutrient digestibility. Dietary treatments consisted of a positive control containing 6.1 and 3.5 g of Ca and nPP, respectively, per kg; a negative control (NC) containing 4.8 and 1.7 g of Ca and nPP, respectively, per kg; the NC diet plus 0.4, 0.8, or 1.2 g of iP from MSP per kg; and the NC diet plus 500, 750, or 1,000 FTU of ECP per kg. Daily gain improved (linear, P < 0.05) with ECP addition, as did apparent digestibility of Ca and P (linear, P < 0.01). Five hundred FTU of ECP per kg was determined to be equivalent to the addition of 0.49 and 1.00 g of iP from MSP per kg in starter pigs diets, based on ADG and bone ash, respectively.     

植酸酶对提高肉仔鸡日粮中钙、磷利用率的研究

将试验肉仔鸡随机分成4组,每组设3个重复,每个重复20只。Ⅰ组为不添加植酸酶的基础日粮对照组;Ⅱ组为每千克日粮添加500U植酸酶替代基础日粮中0.09%的无机磷试验组;Ⅲ组为每千克日粮添加500U植酸酶替代基础日粮中0.11%的无机磷试验组;Ⅳ组为每千克日粮添加500U植酸酶替代基础日粮中0.13%的无机磷试验组。试验按0～3周龄和4～6周龄两个阶段进行。试验结果表明:在肉仔鸡玉米-豆粕型日粮中添加0.01%的植酸酶(活性为5000U/g)替代日粮中0.12%的钙和0.11%的无机磷可显著提高肉仔鸡的生长性能,并能取得最佳的经济效益,为最适替代比例。     

An Escherichia coli phytase expressed in yeast effectively replaces inorganic phosphorus for finishing pigs and laying hens

Two experiments determined the efficacy of an Escherichia coli phytase (ECP) added to P-deficient, corn-soybean meal diets fed to finishing pigs and second-cycle laying hens. Sixty finishing pigs (49 +/- 0.9 kg) were formed into blocks within sex based on weight and ancestry and allotted to a P-deficient diet unsupplemented or supplemented with 0.10% inorganic P (iP) from KH2PO4 or ECP at 250, 500, 1,000, or 10,000 phytase units (FTU)/kg. Individually fed pigs were allowed ad libitum access to the experimental diets until a BW of 120 +/- 3 kg was achieved, at which time the pigs were euthanized and the left fibula and fourth metatarsal were excised for determination of bone ash. Pigs were fed a 2-phase diet program for early- and late-finishing pigs; available P in the basal diets was set 0.10% below the requirement. Dietary supplementation of iP or ECP increased weight gain (P < 0.10) and G:F (P < 0.01); performance was not different (P > 0.13) among the phytase-supplemented groups. Fibula ash was greatest (P < 0.01) for pigs fed diets containing 10,000 FTU of ECP/kg. Two hundred forty second-cycle hens were allotted to a P-deficient diet or a P-deficient diet supplemented with 0.10% iP or ECP at 150, 300, or 10,000 FTU/kg for a 12-wk experiment. The basal diet was a corn-soybean meal diet with no added iP (17% CP, 3.8% Ca, 0.10% available P). Hens fed the P-deficient diet were removed from the experiment after 4 wk due to poor egg production. Supplementation of iP or ECP resulted in increased (P < 0.01) feed intake, egg weight, and egg production during the first 4 wk. During the entire 12-wk period, there were no differences (P > 0.28) between the iP- and ECP-supplemented groups in feed intake, egg weight, or egg production. These experiments reveal that ECP was as efficacious as supplemental iP and that supplementation of an excess dose of ECP was efficacious and without negative effects in finishing pigs and laying hens.     

Distribution of supplemental Escherichia coli AppA2 phytase activity in digesta of various gastrointestinal segments of young pigs

The objective of this study was to determine the functional location and disappearance of activity of a supplemental Escherichia coli AppA2 phytase and its impact on digesta P and Ca concentrations in the gastrointestinal tract of pigs. In Exp. 1, 18 pigs (8.3 +/- 0.2 kg of BW) were allotted to 3 groups (n = 6 each) and fed a low-P (0.4%) corn-soybean meal, basal diet (BD), BD + phytase [500 units (U)/kg of feed], or BD + inorganic P (iP, 0.1%) for 4 wk. In Exp. 2, 30 pigs (14.5 +/- 0.2 kg of BW) were allotted to 3 groups (n = 10 each) and fed BD, BD + 500 U of phytase/kg of feed, or BD + 2,000 U of phytase/kg of feed for 2 wk. Five or six pigs from each treatment group were killed at the end of both experiments to assay for digesta phytase activity and soluble P concentration in 6 segments of the digestive tract and digesta total P and Ca concentrations in stomach and colon. Compared with pigs fed BD, pigs fed BD + 500 U of phytase/kg of feed in Exp. 1 and BD + 2,000 U of phytase/kg of feed in Exp. 2 had greater (P < 0.05) phytase activities in the digesta of the stomach and upper jejunum (2 m aborally from the duodenum). No phytase activity was detected in the digesta of the lower jejunum (2.12 m cranial to the ileocecal junction) or ileum from any of the treatment groups in either trial. Concentrations of digesta-soluble P peaked in the upper jejunum of pigs fed BD in Exp. 1 and 2, but showed gradual decreases between the stomach and the upper jejunum of pigs fed BD + phytase or BD + iP. In both experiments, pigs fed only BD had greater (P < 0.05) colonic digesta phytase activity and soluble P concentrations than those fed phytase. In Exp. 2, total colonic digesta P or Ca concentrations, or both, of pigs displayed a phytase-dose-dependent reduction (P < 0.05). In conclusion, supplemental dietary AppA2 mainly functioned in the stomach and was associated with a reduced phytase activity in colonic digesta of weanling pigs.     

Effect of body weight on phosphorus digestibility and efficacy of a microbial phytase in young pigs.

The effect of body weight on P digestibility and on efficacy of supplemental Aspergillus niger phytase was studied in two experiments with young growing pigs. Excreta were collected quantitatively. All diets contained 2.0 g digestible P per kg dry matter at a maximum and renal P excretion never exceeded 15 mg/d. When dietary P mainly originated from monocalcium-phosphate, both P digestibility and Ca net absorption linearly increased by 3.6 and 5.6 percentage units, respectively, when BW increased from 15 to 35 kg. With a similar range in BW, P digestibility and Ca net absorption were unaffected by BW when P mainly originated from maize, barley and soybean meal. In both types of diet, crude protein digestibility increased with increasing body weight, whereas organic matter digestibility was effected by BW only in the diet containing maize, barley and soybean meal. Phytase (400 U/kg) almost doubled P digestibility when supplemented to a diet with P mainly originating from maize, soybean meal and barley. This effect of phytase supplementation was equal in pigs at 15.7 kg BW (33 vs. 55%) and at 39.1 kg BW (32 vs. 56%). Digestibility of any organic fraction was unaffected by supplemental phytase. With regard to on-farm conditions, it appears eligible from this results to apply digestibility coefficients for P determined in growing-finishing pigs for piglets as well.     

Escherichia coli sepsis and endotoxemia in conscious young pigs

In conscious pigs the influence of intravenous infusion of live E. coli (7×10⁸/kg), of the equivalent amount of endotoxin (20 g/kg) or of a high dose of endotoxin (2.5 mg/kg) on the hemodynamic, clinical and pathological parameters and on survival rate was studied. E. coli and endotoxin infusion resulted in pulmonary hypertension, systemic arterial hypotension, a decrease in cardiac output and an increase in heart rate. Clinical signs were characterized by respiratory and nervous disturbances, whereas necropsy revealed hemorrhages and edema in several organs. Although these findings were similar in the three groups, a marked difference in lethality was observed. Infusion of E. coli or of the high dose of endotoxin resulted in a significant mortality, whereas all pigs survived the infusion of the low dose of endotoxin. This suggests that the lethal pathophysiological mechanisms may only become activated when a sufficient amount of endotoxin is released into the circulation.     

Efficacy of yeast phytase in improving phosphorus bioavailability in a corn-soybean meal-based diet for growing pigs

Crossbred barrows (n = 66; 6 wk old) were used in a 6-wk experiment to evaluate the efficacy of phytase from yeast or Aspergillus niger on performance, tibial characteristics, and serum inorganic P concentration. We also investigated the stability of these phytases in acidic solutions with pepsin, which simulated gastric conditions. Pigs were fed a P-adequate diet containing .34% nonphytate-P or a low-P diet containing .20% nonphytate-P. The low-P diet was supplemented with 0, 1,000, 2,000, or 4,000 phytase units (PU; the activity at optimal pH, i.e., pH 4.2 for yeast phytase and pH 5.5 for phytase from Aspergillus niger)/kg of yeast phytase, or 1,000 PU/kg phytase from Aspergillus niger. The graded level of yeast phytase linearly increased ADG (P = .047), tibial weight (P = .091), tibial density (P < .001), and P concentration in tibial cortex (P = .018). Aspergillus niger phytase also increased ADG (P = .022), serum inorganic P concentration (P < .001), tibial density (P = .007), and tibial P concentration (P = .025). The pigs given 1,000 PU/kg Aspergillus niger phytase showed greater ADG (P = .091), tibial density (P= .001), and tibial P concentration (P = .062) than those given 1,000 PU/kg yeast phytase. No measurements differed (P > .31) between the pigs given 1,000 PU/kg Aspergillus niger phytase and those given 4,000 PU/kg yeast phytase. These results suggested that yeast phytase improves bioavailability of P in the diet for growing pigs but the efficacy of yeast phytase is less than that of Aspergillus niger phytase. During incubation in acidic solutions with pepsin, yeast phytase (P < .001) lost more of its activity than Aspergillus niger phytase. This lesser stability of yeast phytase may be responsible for the poorer efficacy of yeast phytase than that of Aspergillus niger. In summary, supplementation of swine diets with yeast phytase is beneficial, but its efficacy is less than that of Aspergillus niger phytase.     

Effectiveness of an experimental consensus phytase in improving dietary phytate-phosphorus utilization by weanling pigs

Consensus phytase is a new biosynthetic, heat-stable enzyme derived from the sequences of multiple homologous phytases. Two experiments were conducted to determine its effectiveness, relative to inorganic P and a mutant enzyme of Escherichia coli phytase (Mutant-EP), in improving dietary phytate-P availability to pigs. In Exp. 1, 36 pigs (3 wk old, 7.00 +/- 0.24 kg of BW) were fed a low-P corn-soybean meal basal diet plus consensus phytase at 0, 250, 500, 750, 1,000, or 1,250 U/kg of feed for 5 wk. Plasma inorganic P concentration, plasma alkaline phosphatase activity, bone strength, and overall ADG and gain:feed ratio of pigs were improved (P < 0.05) by consensus phytase in both linear (R2 = 0.20 to 0.70) and quadratic (R2 = 0.30 to 0.70) dose-dependent fashions. In Exp. 2, 36 pigs (4 wk old, 9.61 +/- 0.52 kg BW) were fed the basal diet + inorganic P at 0.1 or 0.2%, consensus phytase at 750 or 450 U/kg of feed, Mutant-EP at 450 U/kg of feed, or 225 U consensus + 225 U Mutant-EP/kg of feed. Pigs fed 750 U of consensus phytase or 450 U of Mutant-EP/kg feed had plasma inorganic concentrations and bone strength that fell between those of pigs fed 0.1 or 0.2% inorganic P. These two measures were 16 to 29% lower (P < 0.05) in pigs fed 450 U of consensus phytase/kg of feed than those of pigs fed 0.2% inorganic P. Plasma inorganic P concentrations were 14 to 29% higher (P < 0.05) in pigs fed Mutant-EP vs. consensus phytase at 450 U/kg at wk 2 and 3. In conclusion, the experimental consensus phytase effectively releases phytate P from the corn-soy diet for weanling pigs. The inorganic P equivalent of 750 U of consensus phytase/kg of feed may fall between 0.1 and 0.2%, but this requires further determination.     

High prevalence and widespread distribution of multi-resistant Escherichia coli isolates in pigs and poultry in China

Escherichia coli play an important ecological role within resistant bacteria populations, and can be used as a bio-indicator of antimicrobial resistance. The aim of the present study was to use this feature of E. coli to investigate the prevalence of antimicrobial resistance and the degree of cross-species transmission of bacteria in pigs and poultry in China. A total of 592 E. coli strains, isolated from pigs and poultry (healthy and diseased animals), were tested for resistance to 22 antimicrobials representing eight antimicrobial drug types.E. coli isolates had high rates of resistance to ampicillin (99.5%), doxycycline (95.6%), tetracycline (93.4%), trimethoprim–sulfamethoxazole (74.3%), amoxicillin (65.1%), streptomycin (54.7%), and chloramphenicol (50.2%). Resistance to cephalosporins, quinolones, and aminoglycosides was also quite prevalent. The majority (81%) of isolates demonstrated multi-antimicrobial resistance, most commonly to 5–6 different antimicrobial types. One isolate was resistant to all 22 antimicrobials. Twenty-two cultures exhibiting multi-antimicrobial resistance were analysed by pulsed-field gel electrophoresis (PFGE) to assess their distribution between farms. Three distinct PFGE types were identified, indicating inter-farm transmission of multi-antimicrobial resistant bacteria. The study confirmed the presence and transmission of multi-antimicrobial-resistant E. coli strains amongst pigs and poultry in China and highlights the urgent need for appropriate monitoring programmes.     

外源植酸酶对饲料钙、磷体外消化率的影响

试验在体外条件下,通过胃蛋白酶和胰蛋白酶两步消化法研究了不同水平的外源植酸酶对饲料中钙和磷利用率的影响。结果表明:添加外源植酸酶可显著提高豆粕、花生粕和菜粕中钙和磷的释放量(P<0.01),但对大麦和高粱中无机磷的释放没有显著影响(P>0.01)。其中豆粕、花生粕以及菜粕中钙和磷的释放量随植酸酶添加量的增加而呈线性增加。最后,还构建了饲料中无机磷释放量的预测模型:y=-0.5971+0.0004x1+0.1339x2-0.0526x(3R2=0.78,P<0.01)。     

植酸酶在家禽饲养中的应用

植酸酶能够水解植酸盐,释放出能被动物利用的磷和多种微量元素。它不仅消除植酸的抗营养作用,还提高动物胃肠道消化酶的活性,提高饲料的利用率,减少饲料中添加高水平磷所造成的环境污染。本文综述了植酸酶在禽类饲料中的应用效果和近年来的研究进展。     

A genetically engineered Escherichia coli phytase improves nutrient utilization, growth performance, and bone strength of young swine fed diets deficient in available phosphorus

A 28-d experiment was conducted using 126 crossbred barrows to evaluate the addition of a genetically engineered Escherichia coli phytase to diets that were 0.15% deficient in available P. Growth performance, bone strength, ash weight, and the apparent absorption of P, Ca, Mg, N, energy, DM, Zn, Fe, and Cu were the response criteria. The pigs (2 pigs/pen) averaged 7.61 kg of BW and 30 d of age initially. The low-P basal diet was supplemented with 0, 100, 500, 2,500, or 12,500 units (U) of E. coli phytase/kg of diet, or 500 U of Peniophora lycii phytase/kg of diet. The positive control (PC) diet was adequate in available P. Pigs were fed the diets in meal form. Fecal samples were collected from each pig from d 22 to 27 of the experiment. There were linear and quadratic increases (P < 0.001) in 28-d growth performance (ADFI, ADG, and G:F), bone breaking strength and ash weight, and the apparent absorption (g/d and %) of P, Ca, and Mg (P < or = 0.01 for quadratic) with increasing concentrations of E. coli phytase. Pigs fed the low-P diets containing 2,500 or 12,500 U/kg of E. coli phytase had greater (P < or = 0.01 or P < 0.001, respectively) values for growth performance, bone breaking strength and ash weight, and the apparent absorption (g/d and %) of P, Ca, and Mg than pigs fed the PC diet. The addition of E. coli phytase did not increase the apparent percentage absorption of N, GE, DM, Zn, Fe, or Cu. There were no differences in the efficacy of the E. coli or P. lycii phytase enzymes at 500 U/kg of low-P diet for any criterion measured. In conclusion, there were linear increases in growth performance, bone breaking strength and ash weight, and the apparent absorption of P, Ca, and Mg with increasing addition of E. coli phytase up to 12,500 U/kg of diet. Also, all of these criteria were greater for pigs fed the low-P diets containing 2,500 or 12,500 U of E. coli phytase/kg than for pigs fed the PC diet. The addition of 500, 2,500, or 12,500 U of E. coli phytase/kg of low-P diet reduced P excretion (g/d) in manure by 35, 42, and 61%, respectively, compared with pigs fed the PC diet.     

Corn expressing an Escherichia coli-derived phytase gene: a proof-of-concept nutritional study in pigs

Two experiments were conducted to investigate the concept that the addition of corn expressing an Escherichia coli-derived gene (corn-based phytase; CBP) to a P-deficient diet would improve growth performance and P utilization in pigs. An E. coli-derived microbial phytase (expressed in Pichia pastoris) sprayed onto a wheat carrier (Quantum) was included for comparison. In Exp. 1, forty-eight 10-kg pigs were blocked by BW into 6 blocks and allotted to 8 dietary treatments such that the BW among dietary treatments was similar and given free access to feed for 28 d. The dietary treatments were a negative control (NC) with no inorganic P supplementation; NC + 2, 4, or 6 g of monosodium phosphate/kg; NC + 16,500, 33,000, or 49,500 phytase units (FTU) of CBP/kg; and NC + 16,500 FTU of Quantum/kg. In Exp. 2, twenty-four 13-kg barrows were assigned to the NC, NC + 16,500 or 33,000 FTU of CBP/kg, or NC + 16,500 FTU of Quantum/kg, in a nutrient- and energy-balance study consisting of 5 d of adjustment and 5-d collection periods. The total collection method was used to determine nutrient and energy balance. Addition of CBP to the low-P NC diet linearly increased (P < 0.01) ADG, G:F, and plasma P concentration of pigs during the 28-d study. There was no difference in ADG, G:F, or plasma P concentration between pigs fed the CBP or Quantum phytase at 16,500 FTU/kg. Weight gain, G:F, and plasma P concentration of pigs increased (P < 0.01) with monosodium phosphate supplementation, confirming P deficiency of the NC diet. Linear improvements (P < 0.05) in DM digestibility and energy retention were observed with CBP supplementation of the NC diet. Although there were linear (P < 0.01) and quadratic (P < 0.05) increases in N digestibility, N retention was unaffected by CBP supplementation of the NC diet in growing pigs. Phosphorus and Ca digestibilities and retentions improved linearly and quadratically (P < 0.01) with the addition of CBP to the NC diet. There was no difference in digestive utilization of P or Ca between pigs fed CBP and Quantum phytase at 16,500 FTU/kg. The data showed that the addition of a corn expressing an E. coli-derived gene to a P-deficient diet improved growth performance and indices of P utilization in pigs, and corn expressing phytase was as efficacious as Quantum phytase when supplemented in P-deficient diets for weanling pigs.     

Escherichia coli phytase improves growth performance of starter, grower, and finisher pigs fed phosphorus-deficient diets

Corn-soybean meal-based diets, consisting of a high-P control (HPC) containing supplemental dicalcium phosphate (DCP), a basal diet containing no DCP, and the basal diet plus Escherichia coli phytase at 500 or 1,000 phytase units per kilogram (FTU/kg; as-fed basis) were fed to evaluate growth performance in starter, grower, and finisher pigs. Pigs were blocked by weight and gender, such that average weight across treatments was similar, with equal numbers of barrows and gilts receiving each treatment in each block. In Exp. 1, 48 pigs with an average initial BW of 11 kg, housed individually, with 12 pens per diet, were used to evaluate growth performance over 3 wk. Overall ADG and G:F were increased linearly (P < 0.05) by dietary phytase addition. Final BW and plasma P concentrations at 3 wk also increased linearly (P < 0.05). In Exp. 2, 128 pigs with an average initial BW of 23 kg, housed four pigs per pen, with eight pens per diet, were used to evaluate growth performance over 6 wk. A linear increase in response to phytase was noted for ADG and G:F in all three 2-wk periods, as well as overall (P < 0.05). Percentage of bone ash also showed a linear increase (P < 0.01). In Exp. 3, 160 pigs (53 kg), housed five pigs per pen, with eight pens per diet, were used to evaluate growth performance over 6 wk. A linear increase was detected for final BW, as well as ADG and G:F in the first and second 2-wk periods, and overall (P < 0.01). Twenty-four 15-kg individually housed pigs were used to evaluate total-tract nutrient digestibility in Exp. 4. Daily absorption of P linearly increased (P < 0.05) with phytase supplementation. Results of this research indicate that E. coli phytase is effective in liberating phytate P for uptake and utilization by starter, grower, and finisher pigs.     

The efficacy of an Escherichia coli-derived phytase preparation

Five experiments were conducted to evaluate the effect of an Escherichia coli-derived phytase on phytate-P use and growth performance by young pigs. The first experiment involved time course, pH dependence, and phytase activity studies to investigate the in vitro release of P from corn, soybean meal, and an inorganic P-unsupplemented corn-soybean meal negative control diet. In Exp. 2, which was designed to determine the efficacy of the E. coli-derived vs. fungal phytase-added diets at 0, 250, 500, 750, 1,000, or 1,250 FTU/kg (as-fed basis; one phytase unit or FTU is defined as the quantity of enzyme required to liberate 1 micromol of inorganic P/min, at pH 5.5, from an excess of 15 microM sodium phytate at 37 approximately C) and a positive control diet, eight individually penned 10-kg pigs per diet (12 diets, 96 pigs) were used in a 28-d growth study. The third experiment was a 10-d nutrient balance study involving six 13-kg pigs per diet (four diets, 24 pigs) in individual metabolism crates. In Exp. 4, eight pens (four pigs per pen) of 19-kg pigs per treatment were used in a 42-d growth performance study to examine the effect of adding the E. coli-derived phytase to corn-soybean diets at 0, 500, or 1,000 FTU/kg (as-fed basis) and a positive control (four diets, 128 pigs). In Exp. 5, six 19-kg pigs per treatment were used in a 10-d nutrient balance study to investigate the effects of the E. coli-derived phytase added to diets at 0, 250, 500, 750, or 1,000 FTU/kg (as-fed basis) and a positive control diet (six diets, 36 pigs). The in vitro study showed that the E. coli-derived phytase has an optimal activity and pH range of 2 to 4.5. Inorganic phosphate release was greatest for soybean meal, least for corn, and intermediate for the negative control diet. Dietary supplementation with graded amounts of E. coli-derived phytase resulted in linear increases (P < 0.05) in weight gain, feed efficiency, and plasma Ca and P concentrations in 10-kg pigs in Exp. 2. Phytase also increased P digestibility and retention in the 13-kg pigs in Exp. 3. In Exp. 4, dietary supplementation with E. coli-derived phytase resulted in linear increases (P < 0.05) in weight gain and feed efficiency of 19-kg pigs. Supplementation of the diets of 19-kg pigs with the E. coli-derived phytase also improved Ca and P digestibility and retention in Exp. 5. In the current study, the new E. coli-derived phytase was efficacious in hydrolyzing phytate-P, both in vitro and in vivo, in young pigs.