A new phytase expressed in yeast effectively improves the bioavailability of phytate phosphorus to weanling pigs

We have recently expressed a new phytase enzyme in a yeast system. Three experiments with a total of 140 weanling crossbred pigs were conducted to examine the efficacy of this enzyme in improving the bioavailability of phytate-P in corn-soybean meal diets to young pigs. Experiment 1 compared the efficacy of this new phytase with a commercially available phytase (Natuphos, BASF) for 4 wk at an inclusion level of 1,200 U/kg of diet. Experiment 2 compared the responses of pigs to four doses of the new phytase supplementation (300, 600, 900, and 1,200 U/kg of diet) for 4 wk. Experiment 3 compared the efficacy of this new phytase and Natuphos at a marginally optimal dose (700 U/kg of diet) for 5 wk. A group of pigs were fed the P-deficient basal diet as a negative control in Exp. 1, and a group of pigs were fed the basal diet plus .17 or .22% inorganic P as a positive control in all experiments. In Exp. 1, pigs fed the two sources of phytase had similar ADG (564 vs 567 g), gain/feed (.597 vs .589), plasma inorganic P concentrations (8.9 vs 8.4 mg/dL), and mobility scores (4.25 vs 4.46) that were higher (P < .05) than those of the negative control. In Exp. 2, plasma inorganic P concentration was a fairly linear response to the phytase dose (r > .83) at wk 1 and 2. Overall ADG of pigs also tended to increase with the phytase dose (P = .15). In Exp. 3, pigs fed the two sources of phytase had ADG (483 vs 506 g) similar to that of the positive control (508 g). These two groups also had similar plasma inorganic P concentrations (7.7 vs 7.4 mg/dL) that were lower (P < .05) than those of the positive control group (9.7 mg/dL). There was no significant effect of dietary treatments on ADFI in all three experiments. In conclusion, our new phytase was as effective as Natuphos, at the inclusion level of 700 or 1,200 U/kg of a P-deficient, corn-soybean meal diet, in improving phytate-P utilization by young pigs.     

Dietary phytase increases the true absorption and endogenous fecal excretion of zinc in growing pigs given a corn-soybean meal based diet

We investigated the effect of dietary phytase on the true absorption and endogenous fecal excretion of zinc (Zn) using ⁶⁷Zn in growing pigs given a corn-soybean meal based diet. Ten crossbred barrows were fed the control diet containing 90-mg/kg Zn, 2.3-g/kg phytate-phosphorus and 3.7-g/kg non-phytate-phosphorus or the phytase diet containing similar amounts of Zn and phytate-phosphorus, and 1.4-g/kg non-phytate-phosphorus with 750-PU/kg phytase for 12 h/day. On day 6, the pigs were given 200 g of the corresponding diet labeled by ⁶⁷Zn for 2 h. We measured feed intake, fecal Zn concentration and ⁶⁷Zn abundance for the determination of apparent absorption, true absorption and endogenous fecal excretion of Zn. Although the apparent absorption of Zn did not significantly differ between the dietary groups, the phytase group had significantly more ( P  < 0.05) true absorption of Zn than the control group. The endogenous fecal excretion of Zn tended to be more ( P  = 0.07) in the phytase group than in the control group. These results suggest that dietary phytase improves Zn bioavailability through increasing the true absorption of Zn in growing pigs, which results in stimulating the endogenous fecal excretion of Zn when dietary Zn satisfies its requirement.     

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.     

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.     

Effects of combining three fungal phytases with a bacterial phytase on plasma phosphorus status of weanling pigs fed a corn-soy diet

The objective of this study was to determine possible synergistic effects of supplementing one of three fungal phytases: Aspergillus fumitagus PhyA (AFP),A. niger PhyA (ANP), or Peniophora lyci phytase (PLP) with an Escherichia coli AppA phytase (EP) in diets for pigs. Three experiments, each lasting for 4 wk, were conducted with a total of 106 weanling pigs (5 wk old). The corn-soybean meal basal diet (BD) contained no supplemental inorganic P. In Exp. 1, 35 pigs (8.6 +/- 1.0 kg BW) were fed (as-fed basis) BD + AFP at 750 U/ kg of feed, BD + inorganic P (0.2% P), or BD + PLP at 500, 750, or 1,000 U/kg feed. Pigs fed BD + AFP or BD + 0.2% P had higher (P < 0.05) plasma inorganic P concentrations than those fed BD + PLP at the end of the trial (wk 4). In Exp. 2, 35 pigs (8.1 +/- 0.9 kg BW) were fed BD + AFP, EP, PLP, a 1:1 mix of AFP:EP, or a 1:1 mix of PLP:EP at 500 U/kg. Pigs fed the AFP:EP mixture had growth performance and plasma measures similar to those fed either enzyme alone. Pigs fed the PLP:EP mixture had lower (P < 0.05) plasma alkaline phosphatase activity than those fed BD + PLP. Pigs fed BD + PLP had lower (P < 0.05) plasma inorganic P concentrations than pigs fed BD + EP, and higher (P < 0.05) plasma alkaline phosphatase activity than all other groups at wk 4. In Exp. 3, 36 pigs (9.1 +/- 1.2 kg BW) were fed BD + ANP, EP, or a 1:1 mix of ANP:EP at 500 U/kg feed. Pigs fed the two enzymes together had lower (P < 0.05) plasma inorganic P concentration than those fed BD + EP and lower (P < 0.05) plasma alkaline phosphatase activity than pigs fed BD + ANP at wk 4. In conclusion, although the four phytases showed different effects on plasma P status of weanling pigs, there was no synergistic effect between any of the three fungal phytases and the bacterial phytase on the plasma measures or growth performance under the conditions of the present study.     

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.     

The effectiveness of an Escherichia coli phytase in improving phosphorus and calcium bioavailabilities in poultry and young pigs.

The effectiveness of an Escherichia coli phytase in comparison with a commercially available Aspergillus phytase in improving the bioavailability of phosphorus in broilers, layers and young pigs was studied in three separate experiments. Three basal diets, marginally deficient in dietary P mainly provided as phytate, were formulated. Both phytases were added to the diets at the rate of 500 U/kg diet. The phytases significantly (P < or = 0.05) improved the availability of phytate P to broilers, layers and young pigs. Aspergillus and E. coli phytases enhanced the pre-caecal digestibility of P by 11 and 29% for broilers and 18 and 25% for layers, respectively. Total tract digestibility of P (P balance) was also enhanced but with smaller magnitude. In pigs, total tract digestibility of P was improved by 33 and 34% by Aspergillus and E. coli phytases, respectively. Under the conditions of this study, it was observed that E. coli consistently, though with small magnitude in layers and pigs, enhanced the availability of phytate P at the same range or slightly better than Aspergillus phytase. It was only in pigs that the availability of Ca was significantly (P < or = 0.05) improved by addition of both phytases. It can be concluded that E. coli phytase is highly effective in improving the bioavailability of phytate P to broilers, layers and young pigs. This seems to be based on the high proteolytic stability of the enzyme in the digestive tract, as shown recently.     

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.     

Degradation of phytate in the gut of pigs--pathway of gastro-intestinal inositol phosphate hydrolysis and enzymes involved.

The present study gives an overview on the whole mechanism of phytate degradation in the gut and the enzymes involved. Based on the similarity of the human and pigs gut, the study was carried out in pigs as model for humans. To differentiate between intrinsic feed phytases and endogenous phytases hydrolysing phytate in the gut, two diets, one high (control diet) and the other one very low in intrinsic feed phytases (phytase inactivated diet) were applied. In the chyme of stomach, small intestine and colon inositol phosphate isomers and activities of phytases and alkaline phosphatases were determined. In parallel total tract phytate degradation and apparent phosphorus digestibility were assessed. In the stomach chyme of pigs fed the control diet, comparable high phytase activity and strong phytate degradation were observed. The predominant phytate hydrolysis products were inositol phosphates, typically formed by plant phytases. For the phytase inactivated diet, comparable very low phytase activity and almost no phytate degradation in the stomach were determined. In the small intestine and colon, high activity of alkaline phosphatases and low activity of phytases were observed, irrespective of the diet fed. In the colon, stronger phytate degradation for the phytase inactivated diet than for the control diet was detected. Phytate degradation throughout the whole gut was nearly complete and very similar for both diets while the apparent availability of total phosphorus was significantly higher for the pigs fed the control diet than the phytase inactivated diet. The pathway of inositol phosphate hydrolysis in the gut has been elucidated.     

Phosphorus bioavailability, growth performance, and nutrient balance in pigs fed high available phosphorus corn and phytase

Three experiments were conducted to evaluate P bioavailability, growth performance, and nutrient balance in pigs fed high available P (HAP) corn with or without phytase. The bioavailability of P in normal and HAP corn relative to monosodiumphosphate (MSP) for pigs was assessed in Exp. 1. In a randomized complete block design, 96 pigs (average initial BW 9.75 kg) were fed eight diets for 28 d. The reference and test diets were formulated by adding P as MSP, HAP, or normal corn at 0, 0.75, or 1.5 g/kg to a corn-starch-soybean meal basal diet (2.5 g/kg P) at the expense of cornstarch. Plasma inorganic P concentration responded linearly (P < 0.05) to supplemental P intake. Estimates of P bioavailability from HAP andnormal corn when plasma P was regressed on supplemental P intake were 46 and 33%, respectively. In Exp. 2 and 3, pigs were fed corn-soybean meal-based diets containing HAP corn or normal corn and 0 or 600 units of phytase per kilogram in a 2 x 2 factorial arrangement (two corn sources and two levels of phytase). In Exp. 2, 48 crossbred pigs (barrow:gilt, 1:1) averaging 9.25 kg were used to evaluate growth performance. There were no detectable interactions between corn source and phytase for any of the performance criteria measured. Pigs receiving normal corn had the lowest (P < 0.05) BW and rate of gain. Feed efficiency was lower (P < 0.05) in pigs fed normal compared with those fed the HAP corn phytase-supplemented diet. In Exp. 3, 24 crossbred barrows averaging 14.0 kg were used to evaluate nutrient digestibility. There were no detectable interactions between corn and phytase for any of the N and Ca balance criteria. Nitrogen and Ca retention were improved in pigs receiving HAP corn with phytase (P < 0.05). Retention and digestibility of P was lowest (P < 0.01) for pigs on normal corn diet without phytase. The percentage of P digested and retained was improved and fecal P excretion lowered (P < 0.05) by feeding HAP corn.The results of this study indicate that the bioavailability and balance of P in HAP corn is superior to that of normal corn. The addition of 600 phytase units (Natuphos 600, BASF) to HAP corn-based diets further improved P digestibility and reduced P excretion in pigs.     

The presence of inositol phosphates in gastric pig digesta is affected by time after feeding a nonfermented or fermented liquid wheat- and barley-based diet

The objective was to quantify the retention of digesta and evaluate the degradation of phytate or inositol hexakisphosphate (InsP(6)) and lower inositol phosphates (InsP?, InsP?, InsP?, and InsP?) in the stomach at different times after feeding pigs a fermented liquid diet with microbial phytase or a nonfermented diet with or without microbial phytase. Six barrows fitted with gastric cannulas were used. The experiment was a 3 × 3 Latin square with 3 pigs fed 3 diets during 3 wk in 2 replicates. Each experimental period lasted for 7 d, comprising 3 d of adaptation and 4 d of total collection of gastric digesta. For each pig, the digesta was collected once daily at 1, 2, 3, or 5 h after feeding the morning meal. A basal wheat- and barley-based diet was steam-pelleted at 90°C. The dietary treatments were a nonfermented basal diet (NF-BD), the NF-BD with microbial phytase (750 phytase units of phytase/kg, as-fed basis; NF-BD + phytase), and the NF-BD + phytase fermented for 17.5 h (F-BD + phytase). Gastric InsP?-P was not detected at all in pigs fed F-BD + phytase because of complete InsP? degradation during fermentation of the feed before feeding. Gastric InsP?-P decreased over time (P < 0.05) in pigs fed NF-BD and NF-BD + phytase. The decreases were 45, 54, 56, and 61 percentage points greater at 1, 2, 3, and 5 h, respectively, in pigs fed NF-BD + phytase compared with NF-BD. However, substantial amounts of InsP? still passed into the small intestine in pigs fed NF-BD + phytase, especially within the first hour (estimated to 17% of InsP?-P intake). The accumulation of lower inositol phosphates in gastric digesta was very small for all treatments and at all times because of a rapid and almost complete degradation. In conclusion, phytase addition to the nonfermented diet increased the degradation of gastric InsP?. However, considerable amounts of intact InsP? still passed into the small intestine because of a shortage of time for InsP? degradation in the stomach. Therefore, to increase the apparent digestibility of plant P in dry wheat- and barley-based diets, the development of phytases that can degrade InsP? effectively immediately after ingestion of the feed at an initial gastric pH from 6.5 to 5.0 is needed. Feeding F-BD + phytase compensated for the shortage of time because the InsP? degradation was completed during fermentation before feeding. The degradation of InsP? to InsP? is the bottleneck for plant P utilization in pigs because the degradation of the lower inositol phosphates is rapid and almost complete.     

Effect of low doses of Aspergillus niger phytase on growth performance, bone strength, and nutrient absorption and excretion by growing and finishing swine fed corn-soybean meal diets deficient in available phosphorus and calcium

Two experiments were conducted to evaluate the efficacy of low doses of Aspergillus niger (AN) phytase for growing and finishing pigs fed corn-soybean meal (SBM) diets with narrow Ca:P ratios that were about 0.9 g/kg deficient in available P and Ca. Experiment 1 utilized 120 pigs with an early finisher period from 51.5 +/- 0.2 to 89.7 +/- 0.9 kg of BW and a late finisher period that ended at 122.5 +/- 2.0 kg of BW. During each period, treatments were the low-P diets with 0, 150, 300, or 450 units (U) of AN phytase added/kg of diet, and a positive control (PC) diet. There were linear increases (P < or = 0.001) in bone strength and ash weight, the absorption of P (g/d and %) and Ca (%), and overall ADG (P = 0.01) with increasing concentration of AN phytase. Pigs fed the diets with 150, 300, or 450 U of AN phytase/kg did not differ from pigs fed the PC diet in growth performance overall, and pigs fed the diets with 300 or 450 U of AN phytase did not differ in P and Ca absorption (g/d) or bone ash weight from pigs fed the PC diet. However, only pigs fed the diet with 450 U of AN phytase/kg had bone strength similar to that of pigs fed the PC diet. Experiment 2 utilized 120 pigs in a grower phase from 25.3 +/- 0.1 to 57.8 +/- 0.8 kg of BW and a finisher phase that ended at 107.6 +/- 1.0 kg of BW. Treatments were the low-P diet with AN phytase added at 300, 500, or 700 U/kg of grower diet, and 150, 250, or 350 U/kg of finisher diet, respectively, resulting in treatments AN300/150, AN500/250, and AN700/350. Growth performance and the absorption (g/d) of P and Ca for the grower and finisher phases were not different for pigs fed the diets containing AN phytase and pigs fed the PC diets. However, pigs fed the PC diets excreted more fecal P (g/d, P < or = 0.01) during the grower and more P and Ca (g/d, P < 0.001) during the finisher phases than the pigs fed the diets with phytase. There were linear increases (P < or = 0.05) in bone strength and bone ash weight with increasing concentration of AN phytase. However, pigs fed the PC diets had a greater bone strength and bone ash weight than pigs fed diets AN300/150, AN500/250 (P < or = 0.02), or AN700/350 (P < or = 0.08). There were no treatment responses for N or DM digestibility in either experiment. Phytase supplementation reduced fecal P excretion from 16 to 38% and fecal Ca excretion from 21 to 42% in these experiments. In conclusion, 450 U of AN phytase/kg was effective in replacing 0.9 g of the inorganic P/kg of corn-SBM diet for finishing swine based on bone strength, whereas 300 or 150 U of AN phytase/kg of diet maintained growth performance of grower or finisher pigs, respectively.     

Comparative effects of three phytases on phosphorus and calcium digestibility in the growing pig

Phytase addition to swine diets has generally resulted in a marked increase in phosphorus (P) digestibility and in a reduction of faecal excretion of P. The number of phytases present in the market is growing and the origins of the microbial genes are becoming more diversified. The aim of this study was to compare the effects of 3 different phytases on P and calcium (Ca) digestibility in pigs. The control diet was based on soybean meal, maize and barley. The inclusion levels were 250 (Q1) and 500 U/kg (Q2) for an E. coli phytase (Quantum), 500 U/kg (Nat) for A. niger (Natuphos) and 750 U/kg (Ron) for P. lycii (Ronozyme P). All phytases significantly reduced faecal concentration of P. For Q2 this reduction was significantly higher than for Q1. P digestibility was improved by 13.8, 18.6, 18.3 and 17.9 percentage units by Q1, Q2, Nat and Ron respectively. The P equivalencies, considered as supplemental P digested compared to the non-supplemented diet of Q1, Q2, Nat and Ron were 0.492, 0.732, 0.678 and 0.678 g of available P/kg of feed respectively. Ca digestibility was also significantly improved by the phytases. It can be concluded that the 3 phytase preparations improved the digestibility and the apparent absorption of P and Ca in the growing pig fed a diet containing P exclusively from plant origin. The effect of including 500 U/kg of E. coli phytase on P digestibility was similar to those induced by the A. niger and P. lycii phytases at their recommended levels of 500 and 750 U/kg, respectively.     

Effects of dietary calcium:phosphorus ratios on apparent absorption of calcium and phosphorus in the small intestine, cecum, and colon of pigs

Thirty-two crossbred barrows were used to investigate the effects of dietary Ca:total P (tP) ratios in phytase-supplemented diets on the apparent absorption of P and Ca in the small intestine, cecum, and colon. Three Ca:tP ratio treatments (1.5:1, 1.3:1, or 1.0:1) were created by adjusting the amount of ground limestone added to the basal low-P grower (.39% tP including .07% added inorganic P) and finisher (.32% tP without added inorganic P) diets. All low-P ratio diets were supplemented with Natuphos phytase at 500 units/kg. A positive control diet without phytase supplementation contained adequate P and Ca to meet dietary requirements. At 123 kg, the pigs were slaughtered and the contents of ileum, cecum, and colon were collected. Lowering the dietary Ca:tP ratio in the diets containing phytase linearly increased (P < .01) the apparent absorption (% and g/d) of P in the small intestine, but Ca absorption was not affected. Pigs fed the low-P diet with a Ca:tP ratio of 1.0:1 had an apparent absorption (g/d) of P or Ca similar to that of pigs fed the control diet, which was adequate in Ca and P. Averaged across all diets, the apparent absorption of P was highest when measured at the cecum, and the apparent absorption of Ca was highest when measured at the colon. In conclusion, lowering the dietary Ca:tP ratio to 1.0:1 in a low-P diet containing phytase increased the apparent absorption of P in the small intestine. Furthermore, a significant amount of P was absorbed in the cecum.     

The effects of citric acid on phytate-phosphorus utilization in young chicks and pigs

Several bioassays were conducted with young chicks and pigs fed phosphorus (P)-deficient corn-soybean meal diets. With diets for chicks containing .62% Ca and .42% P (.10% available P), graded doses of a citric acid + sodium citrate (1:1, wt:wt) mixture (0, 1, 2, 4, or 6% of diet) resulted in linear (P < .01) increases in both weight gain and tibia ash. Relative to chicks fed no citric acid, tibia ash (%) and weight gain (g/d) were increased by 43 and 22%, respectively, in chicks fed 6% citric acid. Additional chick trials showed that 6% citric acid alone or sodium citrate alone was as efficacious as the citric acid + sodium citrate mixture and that 1,450 U/kg of phytase produced a positive response in bone ash and weight gain in chicks fed a diet containing 6% citrate. Varying the Ca:available P ratio with and without citrate supplementation indicated that citric acid primarily affected phytate-P utilization, not Ca, in chicks. Moreover, chicks did not respond to citrate supplementation when fed a P-deficient (.13% available P), phytate-free casein-dextrose diet. Young pigs averaging 10 to 11 kg also were used to evaluate citric acid efficacy in two experiments. A P-deficient corn-soybean meal basal diet was used to construct five treatment diets that contained 1) no additive, 2) 3% citric acid, 3) 6% citric acid, 4) 1,450 U/kg phytase, and 5) 6% citric acid + 1,450 U/kg phytase. Phytase supplementation increased (P < .01) weight gain, gain:feed, and metatarsal ash, whereas citric acid addition increased only gain:feed (P < .05) and metatarsal ash (P < .08). A subsequent 22-d pig experiment was conducted to evaluate the effect of lower levels of citric acid (0, 1, 2, or 3%) or 1,450 U/kg phytase addition to a P-deficient corn-soybean meal diet. Phytase supplementation improved (P < .01) all criteria measured. Weight gain and gain:feed data suggested a response to citric acid addition, but this was not supported by fibula ash results (P > .10). The positive responses to phytase were much greater than those to citric acid in both pig experiments. Thus, dietary citric acid effectively improved phytate P utilization in chicks but had a much smaller effect in pigs.     

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.     

不同植酸酶对生长育肥猪生产性能及养分利用的影响

选择"杜×长×大"三元杂交生长猪54头,研究了大肠杆菌、黑曲霉来源植酸酶替代日粮中部分磷酸氢钙对生长育肥猪生长性能、养分消化率、血液生化指标及粪磷、氮排泄的影响。试验猪随机分成对照组、试验Ⅰ组、试验Ⅱ组,每组3个重复。对照组饲喂常规日粮,试验Ⅰ组饲喂低磷+植酸酶Ⅰ的日粮,试验Ⅱ组饲喂低磷+植酸酶Ⅱ的日粮。试验结果表明,在生长育肥猪日粮中添加植酸酶替代部分磷酸氢钙,改善了生长育肥猪生长性能,其中添加大肠杆菌植酸酶显著改善生长育肥猪的生长性能;显著改善了干物质、粗蛋白质、钙、磷、总能的表观消化率,并显著降低了粪中氮、磷的排泄;显著提高了血清中总蛋白、球蛋白、血清磷的浓度,而尿素氮、血清钙浓度显著降低。添加黑曲霉植酸酶后,血糖浓度下降,而碱性磷酸酶的活性无显著变化;添加大肠杆菌植酸酶后,碱性磷酸酶的活性显著降低,而血糖浓度无显著变化。     

Comparison of different levels and sources of microbial phytases

Phytases catalyse the hydrolysis of phytate rendering phosphorus (P) available for absorption. Endogenous plant phytases are to some extent present in cereals (depending on species and varieties) while microbial phytases are added to cereal based diets to increase the digestibility of phytate bound P. The present study compared two different microbial phytases. The basal diet was composed of wheat, barley, soybean and rapeseed meal without feed phosphate. The diet was initially expanded, pelleted at 90 °C and crumbled. Phytases were added at 250, 500 and 750 FTU kg^− 1 diet (Aspergillus niger; Phytase 1) and 375 and 750 FYT kg^− 1 diet (Peniophora lycii; Phytase 2). The experiment comprised 6 treatment groups of 6 pigs each kept in metabolism crates and fed one of the 5 test diets or a diet with no added microbial phytase. The diets were fed for 12 days, 5 days for adaptation and 7 days for total collection of faeces and urine. Phosphorus digestibility of the basal diet averaged 43% and increased to 55, 61 and 66% following addition of 250, 500 and 750 FTU/kg of Phytase 1 and 54 and 60% following addition of 375 and 750 FYT/kg of Phytase 2, respectively. In conclusion, equivalent effects were obtained when Phytase 2 was given at 1.5 times the doses of Phytase 1.     

Water-soluble phosphorus excretion in pigs fed diets supplemented with microbial phytase

Three experiments were conducted to compare the excretion of water-soluble phosphorus (P) of starter, grower, and finisher pigs fed corn-soybean meal-based P-deficient basal diet containing no added inorganic P (B), P-adequate diet (the basal diet with added dicalcium phosphate; B + P), the basal diet plus 500 units of microbial phytase/kg (B + 500), or the basal diet plus 1000 units of microbial phytase/kg (B + 1000). There were 6 barrows per diet, in a randomized complete block design, with an average initial body weight of 10.4, 20.0, or 51.1 kg for each of starter, grower, and finisher pigs in the three phosphorus balance experiments, respectively. In the experiments, the addition of dicalcium phosphate or phytase to the basal diet increased ( P  < 0.05) the digestibility and retention of P, and there were linear reductions ( P  < 0.05) in water-soluble P excretion as a result of supplementing the basal diet with phytase. In the starter pig experiment, phytase addition at 500 or 1000 units/kg reduced ( P  < 0.05) water-soluble P excretion by 28 or 42%, respectively when compared with the B + P diet. In the grower pig experiment, adding phytase at 500 or 1000 units/kg reduced ( P  < 0.05) water-soluble P excretion by 24 or 34%, respectively when compared with the B + P diet. The use of phytase at 500 or 1000 units/kg reduced ( P  < 0.05) water-soluble P excretion by 11 or 30%, respectively in the finisher pig experiment. The proportion of water-soluble phosphorus in total phosphorus was not affected by dietary treatment in any of the three experiments. In conclusion, adding phytase at 1000 units/kg to a corn-soybean meal-based P-deficient diet basal diet containing no added inorganic P compared with B + P diet reduced the daily excretion of water-soluble P in starter, grower, and finisher pigs by 42, 34, and 30%, respectively.     

High dietary phytase levels maximize phytate-phosphorus utilization but do not affect protein utilization in chicks fed phosphorus- or amino acid-deficient diets

Four trials investigated the effect of high levels of three phytase enzymes on P and protein utilization in chicks. The three phytases were derived from Aspergillus (Fungal Phytase 1), Peniophora (Fungal Phytase 2), and E. coli. Within each assay, 8-d-old male chicks were given ad libitum access to their experimental diet for 10 to 14 d. For Trials 1, 2, and 3, the basal diet was a corn-soybean meal diet deficient in P that was analyzed to contain 23% CP and 0.38% total P (0.10% estimated available P, as-fed basis). Phytase supplementation levels were based on the assessment of phytase premix activity (i.e., P release from Na phytate at pH 5.5 and 37 degrees C). In Trial 1, supplementation of inorganic P from KH2PO4 (0 to 0.20%) resulted in a quadratic (P < 0.05) response in weight gain, gain:feed, and tibia ash concentration but a linear (P < 0.01) increase in tibia ash weight. Tibia ash was higher (P < 0.01) for chicks fed E. coli phytase than for those fed Fungal Phytase 1 at 500, 1,000, and 5,000 phytase units (FTU)/kg, but did not differ between these two phytases at 10,000 FTU/kg. In Trial 2, E. coli phytase supplementation at 1,000 FTU/kg maximized growth and bone responses, whereas addition of either of the two fungal phytases resulted in increasing responses up to 5,000 and 10,000 FTU/kg. Dietary addition of Fungal Phytase 2 resulted in the poorest (P < 0.01) responses among the three phytases. Escherichia coli phytase supplementation at 10,000 FTU/kg in Trial 3 resulted in tibia ash (millligrams) responses that were greater (P < 0.05) than those resulting from either 0.35% inorganic P supplementation or 10,000 FTU/kg of Fungal Phytase 1 or 2. Trial 4 showed that E. coli phytase supplementation at either 500 or 10,000 FTU/ kg did not improve protein efficiency ratio (gain per unit of protein intake) of chicks fed low-protein soybean meal or corn gluten meal diets that were first-limiting in either methionine or lysine, respectively. These results demonstrate that high dietary levels of efficacious phytase enzymes can release most of the P from phytate, but they do not improve protein utilization.