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.     

Growth performance and carcass traits of pigs subjected to marginal dietary restrictions during the grower phase.

Sixty-four individually housed pigs were used to investigate the effect of amino acid content of finisher diets on growth performance of pigs subjected to marginal dietary amino acid restrictions (80% of the 1988 NRC lysine recommendation) during the grower phase. In each of the two trials, low- and high-amino-acid grower diets (.421 and .765 g lysine/MJ DE, respectively) and four finisher diets (.421, .516, .612, and .707 g lysine/MJ DE) were randomly assigned within sex to 16 gilts and 16 castrated males weighing 23.0 +/- 2.0 kg in a 2 x 4 factorial arrangement of treatments. The average weight of pigs after a completion of diet change was 50.4 +/- 2.1 kg. All pigs were slaughtered at an average weight of 105.2 +/- 4.1 kg. Ultrasound backfat thickness was measured at the time of diet change and before slaughter. Pigs were allowed ad libitum access to feed and water. During the grower phase, pigs fed the high-amino-acid diet grew faster (P < .001) and more efficiently (P < .001) and had less ultrasound backfat (P < .001) than those fed the low-amino-acid diet. The grower diet had no effect on weight gain during the finisher phase. Consequently, pigs fed the high-amino-acid grower diet had better overall weight gain (P < .01) than those fed the low-amino-acid diet. The rate of lean accretion was, however, similar between the two groups of pigs. Furthermore, pigs fed the low-amino-acid grower diet seemed to have better carcass quality, as indicated by less ultrasound backfat (P < .01) and larger carcass longissimus muscle area (P < .05). Average and 10th rib carcass backfat decreased linearly (P < or = .05) and lean accretion rate improved linearly (P < .05) as the amino acid content of finisher diets increased, but there was no grower x finisher diet interaction in these and other response criteria. Although no evidence of compensatory weight gain was observed, it is possible that compensatory lean tissue growth may have occurred in pigs subjected to early amino acid restrictions at the expense of fatty tissue growth.     

Effects of step-up and step-down phytase regimens on performance and processing yields of male broilers from 1 to 35 d of age

An experiment was conducted to evaluate increasing or decreasing concentrations of dietary phytase on growth performance and processing yields of male broilers from 1 to 35 d of age. Treatments consisted of a positive control, a negative control (NC; less 0.14% Ca, 0.13% nonphytate P, and 0.03% Na), and 6 additional treatments based on the NC supplemented with phytase. Treatments 3 through 5 consisted of the NC diet supplemented with 500 phytase units (FTU)/kg of phytase in the starter phase that was either continued throughout the remainder of the study (treatment 3) or increased to 1,500 FTU/kg beginning in the finisher (treatment 4) or grower (treatment 5) phases. Treatment 6 had 1,500 FTU/kg of phytase throughout the study. Treatments 7 and 8 had 1,500 FTU/kg in the starter and decreased to 500 FTU/kg in the finisher or grower phases, respectively. At 35 d of age, broilers fed diets containing 1,500 FTU/kg of phytase had increased BW gain compared with birds fed diets formulated to contain 500 FTU/kg of phytase. Increasing phytase concentration between the starter and grower phases or decreasing phytase concentration between the grower and finisher phases negatively affected FCR from 1 to 35 d of age. Phytase supplementation did not affect weight and yield of carcass characteristics. Therefore, dietary phytase concentration should not be varied throughout production for optimum growth performance.     

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.     

Foot ash can replace tibia ash as a quantification method for bone mineralization in broilers at 21 and 42 days of age

Prior research indicated that foot ash determinations were as robust as tibia bone ash determinations in reflecting the degree of bone mineralization in chicks at 14 d of age. In the current research, the relative effectiveness of the 2 procedures was evaluated in 21- and 42-day-old broilers while also evaluating a new dietary phytase supplement. In experiment 1, broilers were fed until 21 d of age a negative control diet with 0.24% available phosphorus, a positive control diet with 0.48% available phosphorus, or the negative control diet supplemented with 300, 500, 1,000, or 2,500 phytase units/kg diet. In experiment 2, broilers were fed until 42 d of age negative control diets having 0.275, 0.250, and 0.225 percent available dietary phosphorus in the starter, grower, and finisher periods, respectively, positive control diets having 0.475, 0.450, and 0.425 percent available dietary phosphorus in the starter, grower, and finisher periods, respectively, or the negative control diets supplemented with 500, 1,000, or 2,500 phytase units/kg diet. At 21 and 42 d of age, broilers fed diets supplemented with the 2 highest doses of phytase had foot and tibia ash values equal to those fed the positive control diet and higher than those fed the negative control diet. At 42 d of age, feed conversion and total breast meat yield values for the broilers fed the highest dose of phytase were superior to the values of the birds fed the positive control diet or the diet containing the lowest dose of phytase. The results indicate that adding levels of this new dietary phytase beyond what is necessary for normal bone mineralization enhances feed conversion and that dried foot and tibia bone ash determinations are both reliable in detecting differences in bone mineralization in 21- and 42-day-old broilers.     

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.     

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.     

Effect of a novel phytase on growth performance, bone ash, and mineral digestibility in nursery and grower-finisher pigs

To compare the effectiveness of 2 phytase enzymes (Phyzyme and Natuphos), growth performance, fibula ash, and Ca and P digestibilities were evaluated in 4 studies. The first 3 studies used 832 pigs (i.e., 288 in the nursery phase, initial BW 8.1 kg; 288 in the grower phase, initial BW 24.2 kg; and 256 in the finisher phase, initial BW 57.8 kg) and were carried out over periods of 28, 42, and 60 d, respectively. Dietary treatments in each study consisted of a positive control [available P (aP) at requirement level]; negative control (Ca remained as in the positive control, and aP at 66, 56, and 40% of the requirement for the nursery, grower, and finisher studies, respectively); negative control plus graded levels of Phyzyme [250, 500, 750, or 1,000; measured as phytase units (FTU)/kg] or Natuphos (250 and 500 FTU/kg for the nursery and grower studies, or 500 and 1,000 FTU/kg for the finisher study) plus a very high dose of Phyzyme (tolerance level, at 10,000 FTU/kg) in the nursery and grower experiments. Across the 3 studies, there was no effect of any dietary treatment on ADFI, but the negative control reduced ADG (10%), G:F (7%), and bone ash (8%) compared with the positive control. In the nursery study, phytase addition increased G:F and bone ash linearly (P < 0.01). In the grower study, phytase increased ADG, G:F, and bone ash linearly (P < 0.01). In the finisher study, phytase addition increased ADG and bone ash linearly (P < 0.01) and increased G:F quadratically (P < 0.05); G:F was, on average, 5% greater (P < 0.05) with Phyzyme than with Natuphos. The fourth study was conducted to investigate the P-releasing efficacy of the 2 phytases. The apparent fecal digestibility of P, measured with chromic oxide as an external marker in 35 pigs (55.9 kg of BW), showed that aP increased (P < 0.001) by 0.17 and 0.06 g (+/- 0.023) per 100 FTU consumed for Phyzyme and Natuphos, respectively. Also, Phyzyme at 10,000 FTU/kg was not detrimental to animal health or growth performance. At doses intended for commercial conditions, Phyzyme proved to be effective in releasing phytate bound P from diets, with an efficacy superior to a commercially available enzyme.     

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.     

Nutrient utilization and manure P excretion in growing pigs fed corn-barley-soybean based diets supplemented with microbial phytase

The effect of high levels of microbial phytase supplementation in diets for growing pigs was studied in a 2‐week performance and nutrient digestibility trial involving 28 growing pigs weighing 16.4 ± 1.06 (mean ± SD) kg. Seven corn‐barley‐soybean meal‐based diets consisting of a positive control (PC) formulated to meet or exceed NRC nutrient requirements; a negative control (NC) with non‐phytate P reduced by 0.1% unit from NRC requirement and fed without or with 500 or 1000 U/kg; a doubled negative control (DNC) with no added inorganic P and fed without or with 2000 or 4000 U/kg. Chromic oxide was added as an indigestible marker and all diets were fed as mash. Pigs fed the PC diet had a higher P digestibility compared with those fed the NC (P < 0.02) and the DNC (P < 0.001) diets. Supplementing the NC diet with pyhtase tended to improve P digestibility (P < 0.10). However, addition of phytase to the DNC diet resulted in linear (P < 0.001) and quadratic (P < 0.03) increases in P digestibility with an overall improvement of 8% and 121% at 4000 phytase U/kg of diet, respectively, compared with the PC and DNC diets. Apparent total tract digestibility of N, OM and DM were higher (P < 0.05) in the PC diet compared with the DNC diet, but not the NC diet (P < 0.10). No effect of phytase addition to NC was observed on Ca, N, DM and OM digestibility. Phytase addition to the DNC diet resulted in a linear increase (P < 0.05) in N, DM and OM digestibility but not Ca. Increasing the levels of phytase supplementation in the NC and the DNC diets linearly decreased fecal P (P < 0.05) content by 45 and 42%, respectively. Adding phytase at 1000 or 4000 U/kg increased P retention (P < 0.05) by 14.3 or 15.6% units, respectively, compared with the PC diet. Urinary P excretion was higher in the group fed the PC diet compared with those fed the NC and DNC diets (P < 0.05). The results of this study show that complete removal of inorganic P from growing pig diets coupled with phytase supplementation improves digestibility and retention of P and N, thus reducing manure P excretion without any negative effect on pig performance.     

Comparison of phytase from genetically engineered Aspergillus and canola in weanling pig diets

Ninety-six crossbred pigs with an average weight of 9.0 kg were used in a 5-wk trial to compare the efficacy of genetically engineered Aspergillus ficuum phytase, expressed in Aspergillus niger (Natuphos) or in canola seed (Phytaseed), for enhancing the utilization of phytate P in corn-soybean meal-based diets fed to young pigs and to evaluate the safety of Phytaseed phytase. Three levels of the two sources of phytase (250, 500, or 2,500 U/kg of diet) were added to a corn-soybean meal basal diet containing .35% total P, .09% available P, and .50% Ca. There were six pens per treatment (one barrow and one gilt/pen), except that the diet without added phytase was fed to 12 pens of pigs. Pen feed consumption and BW were recorded weekly. During wk 5, pen fecal samples were collected for determination of apparent digestibilities of DM, Ca, and P. At the end of wk 5, all barrows were killed, and the 10th rib on both sides was removed for determination of shear force and energy. Thirty pigs (six from the diet without added phytase and the diets with 500 and 2,500 U/kg phytase from both sources) were randomly selected for gross necropsy and histologic evaluation of liver, kidney, and bone tissues. Both sources of phytase were equally effective in increasing (P < .05) daily gain, gain:feed, apparent digestibilities of DM, P, and Ca, and 10th rib measurements. Fecal P excretion was reduced with phytase addition. Feed intake was increased by phytase levels during wk 4 to 5. No significant abnormalities were seen in any of the 30 pigs necropsied. The fit of a nonlinear function revealed that most measurements were reaching a plateau at 2,500 U/kg phytase. In summary, based on performance, bone measurements, and digestibilities of P, Ca, and DM of young pigs, the efficiency of Phytaseed was similar to that of Natuphos for enhancing the utilization of phytate P in corn-soybean meal-based diets. General necropsy and histologic examination of tissues indicated no toxic effect of phytase.     

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.     

Effect of phytase on phosphorous balance in 20-kg barrows fed low or adequate phosphorous diets

The effects of phytase on phosphorus (P) digestibility are well established. However, there are few studies that report P balance, particularly when phytase is used in diets that have adequate or deficient P. The main objective of the study was to determine the effect of dietary P levels and exogenous phytase on P balance in growing pigs. The first part of the experiment was a 14-d metabolism study conducted with 80 barrows (initial body weight 18.5 ± 0.5 kg) with a 2 × 5 factorial arrangement of treatments and main effects of available P (0.13% available P, low P [Low-P] diet; 0.35% available P, adequate P [Adeq-P] diet) and phytase (0, 250, 500, 2,500, and 12,500 U/kg). A portion of the pigs (n = 24) fed the Low-P diet, with 0, 500, 2,500, 12,500 U/kg phytase, and those fed the Adeq-P diet, with 0 and 12,500 U/kg phytase, remained on test diets for another 4 d, and tissues were collected for determination of bone characteristics and tissue P concentration. There was a P × phytase interaction for P retention that was accounted for by a lack of response to phytase in pigs fed the Adeq-P diet. Retention of P was greater with incremental levels of phytase in pigs fed Low-P diets as compared to those fed Adeq-P diets (P level × phytase, P < 0.01), but calcium (Ca) retention was greater in pigs fed Adeq-P diets (P level × phytase P < 0.01). Apparent total tract digestibility (ATTD) of P was improved by phytase (P < 0.001) and was greater in pigs fed Adeq-P diets as compared to those fed Low-P diets (P = 0.006). Metatarsal bone ash (quadratic, P = 0.01) and strength (linear, P = 0.03) was increased by phytase addition to the Low-P diets. There were no phytase or dietary P effects on P concentrations of the heart, kidney, liver, muscle, and spleen. These results suggest that as compared to the effects in an Adeq-P diet, adding phytase to a Low-P diet was more effective at reducing the P and Ca excretion and restoring average daily gain (ADG). The P released by phytase is absorbed and contributes to improved bone growth, greater rates of tissue accretion, and increased body weight, but does not change tissue P concentrations. There is, however, a threshold for P retention, beyond which it is excreted in the urine.     

Investigations on genetically modified maize (Bt-maize) in pig nutrition: fattening performance and slaughtering results.

A grower finisher performance trial with forty-eight pigs was designed to compare the growth performance of pigs fed diets containing either genetically modified (GM) Bt-maize (NX6262) or its parental maize (Prelude) line. During the experiment, the pigs were fed with a grower and a finisher diet both containing 70% maize investigated in a previously study which showed that they contained similar ME values and digestibility of crude nutrients. The pigs with an initial live weight of 23.9 +/- 3.0 kg were allotted to single boxes. During a 91 days growing period the pigs of both groups recorded equal performance in daily weight gain (AW) 815 +/- 93 vs. 804 +/- 64 g/d depending on equal amounts of feed intake 1.95 +/- 0.15 vs. 1.94 +/- 0.15 kg/d (parental vs. transgenic). The results confirm equal performance among growing-finishing pigs fed parental or genetically modified maize containing diets. For slaughtering the pigs were divided into 4 groups with a different duration of the finishing period. After slaughtering the carcass characteristic were registered.     

Evaluation of phytase concentration needed for growing-finishing commercial turkey toms

1. Growth performance, serum bone markers, and bone strength and mineralisation were determined in tom turkeys grown from 9 to 17 weeks of age. 2. Dietary non-phytate phosphorus was formulated to be reduced by 1.0 g/kg in the low phosphorus diet compared to a control diet and phytase was added to provide 0, 150, 300, 450 or 600 units/kg activity to the low phosphorus diet. 3. From 9 to 12 weeks of age, body weight and gain:food were reduced by the low phosphorus diet without added phytase, compared to the adequate phosphorus diet. Increasing the concentration of phytase linearly increased these growth parameters. There were no significant growth responses at 17 weeks of age. 4. Serum osteocalcin was reduced by increasing dietary phosphorus at 12 weeks of age when growth was affected, but not at later ages. Serum pyridinoline was reduced by higher dietary phosphorus and decreased linearly with increasing phytase activity at 17 weeks of age. 5. Fracture force of the ulna and femur increased linearly with increasing phytase activity but bone strength was not affected when corrected for bone cross-sectional area. Bone strength of the ulna and ash concentration of the ulna and tibia were increased by higher dietary phosphorus. Humerus and ulna ash increased linearly with increasing phytase activity. 6. Water-soluble phosphorus content of the litter was increased by higher dietary phosphorus and addition of phytase to the low phosphorus diet. The increase in water-soluble phosphorus content of the litter when phytase was fed may indicate that phosphorus could be fed at a lower concentration than used in this trial, at least in the finisher diet when phytase is added to the food. 7. Bone fracture force, strength and ash were generally optimised when 450 units/kg phytase activity was added to the low phosphorus diet. However, growth performance was best in the grower I (9 to 12 weeks) phase when 600 units/kg phytase was added to the diet.     

The influence of dietary field peas (Pisum sativum L.) on pig performance, carcass quality, and the palatability of pork

An experiment was conducted to test the hypothesis that field peas may replace soybean meal in diets fed to growing and finishing pigs without negatively influencing pig performance, carcass quality, or pork palatability. Forty-eight pigs (initial average BW 22.7 +/- 1.21 kg) were allotted to 1 of 3 treatments with 2 pigs per pen. There were 8 replications per treatment, 4 with barrows and 4 with gilts. The treatments were control, medium field peas, and maximum field peas. Pigs were fed grower diets for 35 d, early finisher diets for 35 d, and late finisher diets for 45 d. Pigs receiving the control treatment were fed corn-soybean meal diets. All diets fed to pigs receiving the medium field peas treatment contained 36% field peas and varying amounts of corn; soybean meal was also included in the grower and the early finisher diets fed to pigs on this treatment. In contrast, no soybean meal was included in diets fed to pigs on the maximum field peas treatment, and field peas were included at concentrations of 66, 48, and 36% in the grower, early finisher, and late finisher diets, respectively. Pig performance was monitored within each phase and for the entire experimental period. At the conclusion of the experiment, carcass composition, carcass quality, and the palatability of pork chops and pork patties were measured. Results showed that there were no effects of dietary treatments on ADFI, ADG, or G:F. Likewise, there were no differences in carcass composition among the treatment groups, but gilts had larger (P = 0.001) and deeper (P = 0.003) LM, less backfat (P = 0.007), and a greater (P = 0.002) lean meat percentage than barrows. The pH and marbling of the LM, and the 10th rib backfat were not influenced by treatment, but there was a trend (P = 0.10) for more marbling in barrows than in gilts. The subjective color scores (P = 0.003) and the objective color score (P = 0.06) indicated that dietary field peas made the LM darker and more desirable. Pork chops from pigs fed field peas also had less (P = 0.02) moisture loss compared with chops from pigs fed the control diet. Treatment or sex did not influence palatability of pork chops or pork patties. In conclusion, field peas may replace all of the soybean meal in diets fed to growing and finishing pigs without negatively influencing pig performance, carcass composition, carcass quality, or pork palatability.     

Effects of microbial phytase, low calcium and phosphorus, and removing the dietary trace mineral premix on carcass traits, pork quality, plasma metabolites, and tissue mineral content in growing-finishing pigs

An experiment was conducted to determine the effects of phytase addition, reduced Ca and available P (aP), and removing the trace mineral premix (TMP) on growth performance, plasma metabolites, carcass traits, pork quality, and tissue mineral content in growing-finishing swine. One hundred twenty cross-bred pigs (initial and final BW of 22 and 109 kg, respectively) were allotted to five dietary treatments on the basis of weight within gender in a randomized complete block design. There were three replications of barrows and three replications of gilts, with four pigs per replicate pen. The dietary treatments were as follows: 1) corn-soybean meal (C-SBM), 2) C-SBM with reduced Ca and aP, 3) C-SBM with reduced Ca and aP plus 500 phytase units/kg of diet, 4) Diet 1 without the TMP, and 5) Diet 3 without the TMP. The Ca and aP were reduced by 0.10% in the low Ca and aP diets and the diets with added phytase. Daily gain, hot carcass weight, dressing percent, kilograms of carcass lean, bone ash percent, and bone strength were decreased (P = 0.10), but liver and kidney weight were increased (P = 0.10) in pigs fed diets with reduced Ca and aP; adding phytase reversed these responses (P = 0.10). The Commission Internationale de I'Eclairage L* was decreased (P = 0.09) in pigs fed the low Ca and aP diet plus phytase relative to those fed the control diet. Removing the TMP had no effect on overall growth performance, but it increased (P = 0.03) 10th-rib backfat thickness and fasting glucose and decreased (P = 0.03) carcass length and ham weight. Liver weight and liver weight as a percentage of final BW were not affected when phytase was added to the control diet, but removing the TMP increased liver weight and liver weight as a percentage of final BW; adding phytase reversed these responses (phytase x TMP, P = 0.06). Removing the TMP decreased (P = 0.08) Zn concentrations in the bone, muscle, and liver, and Cu and Fe concentrations in the bile but increased (P = 0.08) Mn concentrations in the bile and liver of pigs. The addition of phytase reversed the negative effects of the reduced Ca and aP diets. These data indicate that removing the TMP in diets for growing-finishing pigs has no negative effects on growth performance or pork quality, but it had negative effects on carcass traits and had variable effects on tissue mineral content.     

Nutrient digestibility and performance responses of growing pigs fed phytase- and xylanase-supplemented wheat-based diets

Three experiments were conducted to evaluate the effect of supplementing phytase and xylanase on nutrient digestibility and performance of growing pigs fed wheat-based diets. In Exp. 1, 10 diets were fed to 60 pigs from 20 to 60 kg of BW to determine the effect of combining phytase and xylanase on apparent total tract digestibility (ATTD) of nutrients and growth performance. The 10 diets included a positive control diet (PC; 0.23% available P; 0.60% Ca) and a negative control diet (NC; 0.16% available P; 0.50% Ca) supplemented with phytase at 0, 250, and 500 fytase units (FTU)/kg and xylanase at 0, 2,000, and 4,000 xylanase units (XU)/kg in a 3 x 3 factorial arrangement. In Exp. 2, 6 ileally cannulated barrows (initial BW = 35.1 kg) were fed 4 wheat-based diets in a 4 x 4 Latin square design, with 2 added columns to determine the effect of combining phytase and xylanase on apparent ileal digestibility (AID) of nutrients. The 4 diets were NC (same as that used in Exp. 1) or NC supplemented with phytase at 500 FTU/kg, xylanase at 4,000 XU/kg, or phytase at 500 FTU/kg plus xylanase at 4,000 XU/kg. In Exp. 3, 36 barrows (initial BW = 55.5 kg) were fed 4 diets based on prepelleted (at 80 degrees C) and crumpled wheat for 2 wk to determine the effect of phytase supplementation on ATTD of nutrients. The 4 diets fed were a PC (0.22% available P; 0.54% Ca) and a NC (0.13% available P; 0.43% Ca) alone or with phytase at 500 or 1,000 FTU/kg. All diets in the 3 experiments contained Cr(2)O(3) as an indigestible marker. No synergistic interactions were detected between phytase and xylanase on any of the response criteria measured in Exp. 1 or 2. There were no dietary effects on growth performance in Exp. 1. In Exp. 1, phytase at 250 FTU/kg increased the ATTD of P and Ca by 51 and 11% at 20 kg of BW or by 54 and 10% at 60 kg of BW, respectively, but increasing the level of phytase to 500 FTU/kg only increased (P < 0.05) ATTD of P at 20 kg of BW. In Exp. 2, phytase at 500 FTU/kg increased (P < 0.05) the AID of P and Ca by 21 and 12%, respectively. In Exp. 3, phytase at 500 FTU/kg improved (P < 0.05) ATTD of P by 36%, but had no further effect at 1,000 FTU/kg. Xylanase at 4,000 XU/kg improved (P < 0.05) AID of Lys, Leu, Phe, Thr, Gly, and Ser in Exp. 2. In conclusion, phytase and xylanase improved P and AA digestibilities, respectively, but no interaction between the 2 enzymes was noted.     

Effect of microbial phytase addition with or without the trace mineral premix in nursery, growing, and finishing pig diets

Two experiments were conducted to determine the interactive effects of phytase with and without a trace mineral premix (TMP) in diets for nursery, growing, and finishing pigs on growth performance, bone responses, and tissue mineral concentrations. Pigs (initial and final BW of 5.5 and 111.6 kg [Exp. 1] or 5.4 and 22.6 kg [Exp. 2]) were allotted to treatments on the basis of BW with eight (Exp. 1) or six (Exp. 2) replications of six or seven pigs per replicate pen. Pigs were started on the diets the day of weaning (average of 18 d). In both experiments, the treatments were with or without 500 phytase units/kg of diet and with or without the TMP in a 2 x 2 factorial arrangement. The Ca and available P concentrations were decreased by 0.10% in diets with phytase. The nursery phase consisted of Phase I (7 d), Phase II (14 d), and Phase III (13 d) periods. In Exp. 1, 26 of 52 pigs fed the diet without the TMP and without phytase had severe skin lesions and decreased growth performance; therefore, pigs fed this diet were switched to the positive control diet. In Exp. 2, the treatment without the TMP and without phytase had 12 replications instead of six. At the end of Phase III, half these replications were switched to the positive control diet and half were switched to the diet without the TMP but with phytase. In Exp. 1 during Phases II and III and in the overall data, pigs fed the diet without the TMP had decreased ADG and ADFI, but the addition of phytase prevented these responses (phytase x TMP; P < 0.02). Growth performance was not affected by diet during the growing-finishing period. Coccygeal bone Zn and Na concentrations were decreased (P < 0.09) in pigs fed the diet without the TMP, and adding phytase increased (P < 0.03) Zn and Fe concentrations. In Exp. 2 during Phases I and II, pigs fed the diet without the TMP had decreased ADG, but the addition of phytase prevented this response (phytase x TMP; P < 0.10). Pigs fed the diet without the TMP had decreased (P < 0.10) ADG (Phase II and overall), ADFI (Phases II and III and in the overall data), and G:F (Phase III). Coccygeal bone Zn and Cu concentrations were decreased (P < 0.09) in pigs fed the diet without the TMP, and adding phytase increased (P < 0.03) Zn concentration in the bones. These data indicate that removing the TMP in diets for nursery pigs decreases growth performance and bone mineral content, and that phytase addition to the diet without the TMP prevented the decreased growth performance.     

Phytase improves iron bioavailability for hemoglobin synthesis in young pigs.

Dietary phytase supplementation improves bioavailabilities of phytate-bound minerals such as P, Ca, and Zn to pigs, but its effect on Fe utilization is not clear. The efficacy of phytase in releasing phytate-bound Fe and P from soybean meal in vitro and in improving dietary Fe bioavailability for hemoglobin repletion in young, anemic pigs was examined. In Exp. 1, soybean meal was incubated at 37 degrees C for 4 h with either 0, 400, 800, or 1,200 units (U) of phytase/kg, and the released Fe and P concentrations were determined. In Exp. 2, 12 anemic, 21-d-old pigs were fed either a strict vegetarian, high-phytate (1.34%) basal diet alone, or the diet supplemented with 50 mg Fe/kg diet (ferrous sulfate) or phytase at 1,200 U/kg diet (Natuphos, BASF, Mt. Olive, NJ) for 4 wk. In Exp. 3, 20 anemic, 28-d-old pigs were fed either a basal diet with a moderately high phytate concentration (1.18%) and some animal protein or the diet supplemented with 70 mg Fe/kg diet, or with one of two types of phytase (Natuphos or a new phytase developed in our laboratory, 1,200 U/kg diet) for 5 wk. In Exp. 2 and 3, diets supplemented with phytase contained no inorganic P. In Exp. 1, free P concentrations in the supernatant increased in a phytase dose-dependent fashion (P<.05), whereas free Fe concentrations only increased at the dose of 1,200 U/kg (P<.10). In Exp. 2 and 3, dietary phytase increased hemoglobin concentrations and packed cell volumes over the unsupplemented group; these two measures, including growth performance, were not significantly different than those obtained with dietary supplemental Fe. In conclusion, both sources of phytase effectively degraded phytate in corn-soy diets and subsequently released phytate-bound Fe from the diets for hemoglobin repletion in young, anemic pigs.