Effects of a New Recombinant Phytase on the Performance and Mineral Utilization of Broilers Fed Phosphorus-Deficient Diets

An experiment was conducted with Arbor Acres broiler chickens that were fed 3 experimental diets—a control diet containing an adequate level of available phosphorus (AP) and 2 diets that were deficient in AP but supplemented with phytase at a level of either 500 or 750 phytase units/kg—to assess the effects of a novel microbial phytase supplement in broilers fed AP-deficient diets on growth performance and mineral utilization. Similar average daily gain, feed intake, and feed efficiency (P > 0.05) were obtained among broilers fed different diets. Compared with broilers fed the control diet, broilers fed diets with phytase had greater (P < 0.05) retention of Ca, P, and Zn. Moreover, the levels of Cu, Zn, Mg, and Mn in the tibia bone at 28 d of age, and Zn and Mn at 42 d of age in birds fed diets with phytase exceeded (P < 0.05) those of birds fed the control diet. Supplementation of phytase increased Zn and Mg contents in the plasma at 42 d of age. Birds responded similarly to phytase supplemented at a level of 500 or 750 phytase units/kg in terms of growth performance, mineral retention, and mineral content in the serum and bone. Therefore, with the supplementation of this novel phytase, it is possible to reduce the dietary levels of P and other minerals to below the recommended levels of the Feeding Standard of Chicken in P. R. China (ZB B 43005-86).     

Evaluation of the Nutrient Matrix Values for Phytase in Broilers

Microbial phytase has been shown to increase the availability of Ca, P, ME, and amino acids (AA) in diets for broilers. However, much more research has been conducted on the Ca and P effects than on the ME and AA effects. Therefore, 2 experiments were conducted to evaluate the effect of phytase on the release of ME and AA from corn-soybean meal diets for broilers. Experiment 1 was a battery study that lasted for 14 d and included diets adequate in all nutrients, diets deficient in ME and AA, and these later 2 diets with and without added phytase. Experiment 2 was a floorpen study that lasted 42 d and included diets with reduced levels of ME and AA with added phytase. Growth performance, meat quality, and tibia ash were not affected by using the ME and AA values for phytase. Total P, soluble P, and inorganic soluble P in the litter were reduced when phytase was added to the diets. These data indicate that ME and AA values for phytase can be used in diet formulations for broilers with no loss in growth or yield performance, but a decrease in the P content of the litter will be observed.     

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.     

Impacts of calcium and phosphorus concentration,their ratio,and phytase supplementation level on growth performance,foot pad lesions,and hock burn of broiler chickens

Concerns about the environment, nutrition, and farm profits all point to the increasing importance of the phosphorus (P) content of a diet. Animals must now be fed near their P requirements. However, it is very difficult to know the exact P requirements of broilers. The objective of this study was to provide efficacy data of a 6-phytase for use in broilers at different Ca levels and Ca/P ratios. Broilers were randomly assigned to 6 treatments, each with 6 replicates. The treatments comprised diets differing in Ca and P level: 1) normal Ca and total normal phosphorus (Pt) level, 2) normal Ca and low Pt level, 3) low Ca and Pt level, and differing in phytase level (no, normal or high phytase supplementation). During the entire study, lowest BW was obtained when broilers were given the imbalanced (normal Ca and low Pt level) diet with low phytase supplementation. Among the balanced dietary treatments no significant effects on performance were observed. A higher Ca/Pt ratio decreased feed intake, whereas addition of phytase increased feed intake. For the starter period, the most favorable feed conversion was obtained when broilers were fed the imbalanced diet with a high dosage of phytase or the low Ca, low Pt diet supplemented with phytase. For the grower and finisher period, broilers with the highest weight gain had the highest feed intake resulting in comparable feed conversions between treatments. Litter quality was not affected by dietary treatments but prevalence of foot pad lesions and hock burn was significantly influenced by treatments. The highest percentage of both was seen when broilers were given the imbalanced diets. The overall results of this study emphasises the relevance of the Ca/P ratio in modern broiler feeding and P studies. It can be concluded from this study that dietary Ca and P concentrations can be reduced by 20% if done in a balanced way. If done in combination with phytase supplementation, performance results improve even more.     

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.     

植酸酶和柠檬酸对肉鸡生产性能及钙、磷利用率的影响

试验以正常营养水平饲粮为对照 ,研究在低营养水平饲粮中添加植酸酶 (0、 30 0g/t)、柠檬酸 (0、 0 5% )对肉鸡生产性能和钙、磷利用率的影响。试验用 2 2 5羽 1日龄黄羽肉鸡随机分为 5个处理 ,每处理 3个重复 ,每重复 1 5只鸡进行 6周试验。结果饲粮营养水平降低 6 %可导致肉鸡日增重 (ADG)和饲料利用率下降 (P <0 0 5) ;在低营养水平日粮中 ,添加 30 0g/t植酸酶、 0 5 %柠檬酸 ,ADG和料肉比 (F/G)与正常营养水平饲粮组差异不显著 (P >0 0 5) ;各处理组的血清Ca、P、AKP活性及胫骨Ca、P差异不显著 (P >0 0 5) ;腿病发生率各处理组差异不显著 (P >0 0 5)。添加 30 0g/t植酸酶、 0 5 %柠檬酸的处理组P排泄量显著低于对照组 (P <0 0 5)。植酸酶与柠檬酸合用能进一步提高生产性能和钙、磷利用率 ,能达到正常营养水平饲粮的效果。植酸酶与柠檬酸合用存在协同效应     

Effect of increasing supplemental phytase concentration in diets fed to Hubbard × Cobb 500 male broilers from 1 to 42 days of age

Phytase supplementation beyond the standard doses used for phosphorus release has been reported to result in extraphosphoric effects by enhancing nutrient digestibility resulting in improved performance of broilers. A study was conducted to examine the effects of the progressive addition of an enhancedEscherichia Coli phytase (400–1,600 phytase units; FTU) on growth performance and carcass characteristics from 1 to 42 d of age in male broilers. One thousand four hundred Hubbard × Cobb 500 1-d-old chicks were randomly distributed into 56 floor pens (0.08 m²/bird). Seven dietary treatments were provided in a 3-phase feeding program consisting of (1) a positive control (adequate Ca and nonphytate P; PC); (2) 1 negative control (Ca and nonphytate P reduced by 0.14% and 0.13%; NC); (3 to 6) the NC diet with 4 increasing supplemental phytase concentrations (NC + 400 FTU, NC + 800 FTU, NC + 1,200 FTU, and NC + 1,600 FTU, respectively); and (7) a low-energy NC diet without phytase and xylanase (reduced 66 kcal of AME_n/kg). Body weight gain, feed conversion, mortality, weight and yield of whole carcass, abdominal fat, and pectoralis major and minor muscles were evaluated. Progressive supplementation of phytase decreased cumulative FCR linearly. Broilers fed diets containing 1,600 FTU had heavier total breast meat by 49 g compared with birds receiving the PC diets. Broilers consuming the NC + 400 FTU or the low-energy NC diet had similar growth performance and meat yield compared with birds provided PC diet. These data indicated that phytase supplementation beyond the need for phosphorus enhances growth performance and carcass characteristics.     

Effects of a new recombinant phytase on performance and mineral utilization of laying ducks fed phosphorus-deficient diets

An experiment was conducted to evaluate the effects of a new phytase supplementation in Jinding laying ducks fed different concentrations of non-phytate P (NPP) on production performance, mineral retention, and bone and plasma minerals. A 14-wk experiment was conducted using 200-d-old female laying ducks. A total of 1,000 laying ducks were randomly allocated to 5 treatments and fed 5 diets: a control diet that contained an adequate concentration of NPP (0.45%) and 4 diets that were deficient in NPP (0.38, 0.32, 0.25, and 0.18%, respectively) but supplemented with phytase at 500 U/kg. Decreasing the NPP content from 0.45 to 0.18% in the diets with phytase supplementation had no detrimental effects on performance. However, Cu and Zn retention was significantly lower (P < 0.05) for laying ducks consuming the 0.18% NPP diet with phytase supplementation. Likewise, laying ducks fed the 0.18% NPP diet had a significant reduction in bone ash, Ca, P, and Cu contents, and in serum P and Cu (P < 0.05). Furthermore, the decrease in NPP content in the diet with phytase supplementation significantly increased (P < 0.05) P retention. Therefore, with the supplementation of this novel phytase at 500 U, it is possible to reduce dietary concentrations of NPP to 0.25% and maintain the normal performance of laying ducks.     

Influence of phytate level on broiler performance and the efficacy of 2 microbial phytases from 0 to 21 days of age

Phytate is an antinutrient in animal feeds, reducing the availability and increasing the excretion of nutrients. Phytases are widely used to mitigate the negative influences of phytate. This trial was designed to compare the efficacy of 2 Escherichia coli-derived phytases on broiler performance and bone ash as influenced by dietary phytate level. A total of 1,024 Arbor Acres male broilers were used with 8 replicate pens of 16 birds/pen. Experimental diets were based on low available phosphorus (avP; 1.8 g/kg) with low (6.40 g/kg) or high (10.65 g/kg) phytate. The low-avP diets were then supplemented with mono-dicalcium phosphate to increase the avP level to 4.5 g/kg, 500 phytase units/kg of phytase A, or 500 phytase units/kg of phytase B to create 8 experimental diets. Feed intake, BW gain, FCR, and livability were influenced by a P source × phytase interaction. Feed intake, BW gain, and livability were reduced and FCR was higher in broilers fed low-avP diets, particularly in the presence of high phytate. Phytase A or phytase B improved feed intake, BW gain, and FCR, particularly in the high-phytate diet. However, broilers fed phytase A ate more and were heavier than broilers fed phytase B. Tibia ash was lowest in broilers fed the low-avP diet and highest in broilers fed the diet supplemented with mono-dicalcium phosphate. Phytase increased tibia ash, and broilers fed phytase A had an increase in tibia ash compared with broilers fed phytase B. In conclusion, high dietary phytate reduced broiler performance. Phytase A and phytase B improved bone ash and growth performance, especially in the high-phytate diets. However, phytase A was more efficacious than phytase B, regardless of the level of phytate.     

Effects of Dietary Phosphorous and Trace Mineral Source on Immune Function,Mineral Status,and Performance of Stressed Steers

Two experiments were conducted to determine the effects of dietary P and trace mineral source on immune response, mineral status, and performance in steers stressed by weaning and disease exposure. In Experiment 1, 24 Angus and 24 Simmental weaned steers were used. Treatments consisted of 1) inorganic trace minerals, 2) organic trace minerals, 3) 0.15% supplemental P + inorganic trace minerals, and 4) 0.15% supplemental P + organic trace minerals. Copper, Mn, and Zn were added to provide 10, 25, and 25 mg/kg DM, respectively. The organic treatments supplied 50% of the supplemental Cu and Mn, and 66% of the supplemental Zn from metal proteinates, with the remainder supplied by inorganic sulfate forms. Inorganic treatments supplied all of the supplemental Zn, Cu, and Mn from sulfate forms. The basal diet was a corn silage-soybean meal-based diet. On d 2 following weaning, steers received an intranasal inoculation of infectious bovine rhinotracheitis virus (IBRV). Rectal temperatures in response to IBRV inoculation were similar across treatments. On d 9, steers were injected with 10 ml of a 25% pig red blood cell (PRBC) suspension. Total Ig titers against PRBC concentrations were higher (P<0.05) in steers receiving no supplemental P on d 7 postinjection. However, IgG and IgM titers were unaffected by treatment. Cell-mediated immune response (CMI) to phytohemagglutinin (PHA), plasma Cu and Zn concentrations, and 38-d performance were unaffected by treatment. In Experiment 2, 35 Angus steers were fed diets containing either inorganic or organic trace minerals. Performance and percent morbidity were unaffected by treatment. Plasma Cu was higher for steers fed organic trace minerals. Results indicate that increasing dietary P or replacing inorganic trace minerals with organic forms had little effect on immunity or performance of steers stressed by weaning.     

不同植酸酶对饲喂低磷日粮肉鸡生长性能及粪N、P排泄的影响

采用306只艾维茵肉鸡研究低磷日粮中添加两种不同植酸酶对肉鸡生产性能、养分利用率及氮、磷排泄的影响。试验共分3个处理组,即对照组、试验Ⅰ组和试验Ⅱ组,每个处理组3个重复,每个重复34只鸡。对照组饲喂正常磷水平的日粮;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,添加植酸酶替代日粮中部分无机磷,肉鸡的日增重和日采食量与对照组相比降低,但差异不显著（P＞0.05）;提高了肉鸡的存活率（P＜0.05）和钙、磷利用率（P＜0.05）;同时氮利用率有一定程度改善（P＞0.05）,显著减少了氮、磷的排泄量（P＜0.05）。添加植酸酶Ⅰ与添加植酸酶Ⅱ相比,肉鸡的日增重与日采食量提高（P＜0.05）,氮的排泄量显著降低（P＜0.05）,磷的排泄量没有差异。     

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.     

Influence of enzyme supplementation of maize-soyabean meal diets on carcase composition, whole-body nutrient accretion and total tract nutrient retention of broilers

1. Carcase composition, whole body nutrient accretion rates and total tract nutrient retention of broilers in response to supplemental phytase or carbohydrase and protease from 0 to 21 d of age were investigated. 2. A total of 480 broilers were allocated to 4 slaughter groups (SG) of 30, 150, 150 and 150 broilers. Thirty broilers, in 6 replicates of 5 birds, comprised the initial SG killed at d 0; 150 broilers were allocated to each of the d 7, 14 and 21 final SG. Broilers in the final SG were allocated to 5 treatments in a randomised complete block design; each treatment had 6 replicate cages of 5 broilers per replicate cage. 3. The diets were maize-wheat-soyabean based and the treatments were: (1) positive control which met NRC (1994) energy and nutrients requirements for broiler, (2) negative control (NC) deficient in metabolisable energy (ME) and P, (3) NC plus phytase added at 1000 FTU/kg, (4) NC plus cocktail of xylanase, amylase and protease (XAP), and (5) NC plus phytase and XAP. 4. Except for ash and Ca, the treatments had no effect on carcase composition. Phytase or XAP individually or combined had variable effects on body nutrient accretion rates at various age periods of the broilers compared with the NC diet. Phytase alone or combined with XAP consistently improved body accretion rates of DM, protein, fat, ash, Ca, and P. 5. Addition of phytase alone or combined with XAP to the NC diet improved total tract N and P retention compared with the NC diet. Cocktail of XAP alone or combined with phytase improved Ca retention. Combination of phytase and XAP improved metabolisable energy (ME) and dry matter retention. 6. Overall, the results showed that the exogenous enzymes used had greater effects on the rates of nutrient accumulation in the carcase rather than on the proportion of nutrients deposited in the carcase.     

玉米-豆粕型日粮中添加高剂量植酸酶对肉鸡养分利用率的影响

本试验研究了玉米-豆粕型日粮中添加高剂量不同水平的植酸酶对0~3和4~6周肉鸡养分利用率的影响。选用1日龄AA肉鸡公雏576只,随机分为6组,每组8个重复,每个重复12只。试验日粮分0~3和4~6周两个阶段,6个处理组:正对照组(前期为总磷0.69%,0.45% NPP;后期为总磷0.59%,0.35% NPP);负对照组(前期总磷0.60%,0.35% NPP;后期为总磷0.49%,0.25% NPP);4个试验组在负对照日粮中分别添加500、2000、8000和32000 FTU/kg 4种植酸酶水平。结果显示:①日粮添加高剂量不同水平的植酸酶显著影响生长前期(17~21日龄)肉鸡的钙、磷的消化利用率(P<0.05),随着植酸酶添加水平增加,钙的消化利用率显著增加(P＜0.05)。②日粮添加高剂量不同水平的植酸酶显著影响38~42日龄肉鸡磷的消化利用率(P＜0.05)。在负对照组日粮中随着植酸酶水平添加的提高,钙的消化利用率呈现先增加后降低的趋势,磷的养分利用率反而显著减少。③日粮添加高剂量不同水平植酸酶显著增加生长前期(17~21日龄)肉鸡的粗蛋白质的消化利用率和表观代谢能(P＜0.05),在生长后期(38~42日龄)对肉鸡的粗蛋白质的消化利用率和表观代谢能提高达到显著水平(P ＜0.05)。因此,高剂量不同水平的植酸酶显著提高肉鸡AME和粗蛋白质、钙、磷的消化利用率,添加高水平植酸酶可以适当调低日粮能量和蛋白质水平,日粮中总磷(tP)水平应低于NRC标准,减少无机磷和钙的添加量,以提高钙、磷在体内的存留量。     

肉仔鸡低钙磷日粮添加植酸酶的研究

选取160只1日龄AA肉仔鸡,随机分成4组,研究在低钙、磷日粮和正常钙、磷日粮中添加植酸酶对肉仔鸡生产性能及钙、磷利用的影响。结果表明：植酸酶显著提高了肉仔鸡的日增重和采食量,并且以采食低钙、磷加酶日粮的肉仔鸡增重效果最为明显（P＜0．01）;显著降低了采食低钙、磷日粮肉仔鸡的料重比（P＜0．05）。采食低钙、磷加酶日粮肉仔鸡的胫骨灰分、钙含量和血清总钙、无机磷浓度显著提高（P＜0．05）;但采食正常钙、磷加酶日粮肉仔鸡上述胫骨与血清指标变化不大,表明植酸酶促进了肉仔鸡对低钙、磷日粮中钙和磷的吸收利用。     

Influence of phytase and xylanase supplementation of a wheat-based diet on ileal and total tract digestibility in growing pigs

The effect of phytase and xylanase supplementation of a wheat-based pig diet on the ileal and total tract apparent digestibility of dietary components and minerals were studied in eight growing pigs fitted with a PVTC cannula in a randomized block design experiment. The diets (A and B) were similar in major ingredient composition and in nutrient content. In diet A, part of the limestone was replaced with di-calcium phosphate to increase the content of available phosphorus (P). Diet B was fed without or with supplementation with phytase (500 FTU/kg; diet BP), xylanase (4000 XU/kg; diet BX) and phytase + xylanase (500 FTU and 4000 XU/kg; diet BPX). There were no differences (P > 0.05) between diets in the ileal or total tract digestibility of organic matter (OM), NDF and crude protein (CP). The ileal and total tract digestibility for P and Ca differed (P < 0.05) between diets, while there were no treatment effects for Zn. The ileal and total tract digestibility for P and Ca was higher (P < 0.05) on diets BP and BPX than on the other diets. In conclusion, phytase improved the utilization of dietary P and Ca in a wheat-based diet, while xylanase had no additional benefits in terms of OM and CP digestibility or mineral utilization. Phytase had no effect on the digestibility of OM, CP or NDF.     

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.     

微量元素添加模式对肉鸡生长性能、微量元素代谢和血浆抗氧化性能的影响

本试验旨在研究不同微量元素添加模式对肉鸡生长性能、微量元素代谢和血浆抗氧化性能的影响。选取720羽1日龄科宝(Cobb-500)肉鸡,随机分为4个组,每个组10个重复,每个重复18只鸡。行业标准组:按照农业行业标准NY/T 33—2004添加铜、铁、锌和锰。NRC标准组:按照NRC(1994)推荐量添加铜、铁、锌和锰。NRC比例组:实测基础饲粮中铜、铁、锌、锰的含量,以过量最多的铜(相对于NRC标准)的倍数补齐其余3种元素。相对生物学效价组:假设基础饲粮中微量元素的生物学利用率为额外添加硫酸盐的30%,对其含量进行校准后按照NRC比例组的方法添加。微量元素都以硫酸盐形式添加,试验期42 d。结果表明:1)不同微量元素添加模式未对肉鸡生长性能和死亡率造成显著差异(P0.05)。2)21日龄时,NRC比例组肉鸡十二指肠铜转运蛋白1(Ctr1)的mRNA相对表达量显著高于其余各组(P0.05),NRC比例组和相对生物学效价组肉鸡十二指肠二价金属转运蛋白1(DMT1)的mRNA相对表达量显著高于其余2组(P0.05);42日龄时,NRC标准组和相对生物学效价组肉鸡十二指肠DMT1的mRNA相对表达量显著高于其余2组(P0.05);各组间21和42日龄肉鸡十二指肠锌转运蛋白1(Zn T1)和锌转运蛋白5(Zn T5)的mRNA相对表达量没有显著差异(P0.05)。3)21日龄时,NRC比例组和相对生物学效价组肉鸡血浆总抗氧化能力(T-AOC)显著高于其余2组(P0.05);42日龄时,与相对生物学效价组相比,NRC比例组肉鸡血浆过氧化氢酶(CAT)活性显著下降(P0.05)。4)粪便中微量元素浓度和饲粮的微量元素添加浓度存在显著的正相关关系(P0.05)。由此可见,从微量元素吸收效率和肉鸡血浆抗氧化性能来看,考虑基础饲粮微量元素相对生物学效价并按NRC比例添加是更适宜的添加模式,同时减少了粪便中微量元素的排泄。     

Effect of microbial phytase on energy availability,and lipid and protein deposition in growing swine

Two experiments were conducted to determine the effect of phytase on energy availability in pigs. In Exp. 1, barrows (initial and final BW of 26 and 52 kg) were allotted to four treatments in a 2 x 2 factorial arrangement. Corn-soybean meal (C-SBM) diets were fed at two energy levels (2.9 and 3.2 x maintenance [M]) with and without the addition of 500 phytase units/kg of diet. The diets contained 115% of the requirement for Ca, available P (aP), and total lysine, and Ca and aP were decreased by 0.10% in diets with added phytase. Pigs were penned individually and fed daily at 0600 and 1700, and water was available constantly. Eight pigs were killed and ground to determine initial body composition. At the end of Exp. 1, all 48 pigs were killed for determination of carcass traits and protein and fat content by total-body electrical conductivity (TOBEC) analysis. Six pigs per treatment were ground for chemical composition. In Exp. 2, 64 barrows and gilts (initial and final BW of 23 and 47 kg) were allotted to two treatments (C-SBM with 10% defatted rice bran or that diet with reduced Ca and aP and 500 phytase units/kg of diet), with five replicate pens of barrows and three replicate pens of gilts (four pigs per pen). In Exp. 1, ADG was increased (P < 0.01) in pigs fed at 3.2 x M. Based on chemical analyses, fat deposition, kilograms of fat, retained energy (RE) in the carcass and in the carcass + viscera, fat deposition in the organs, and kilograms of protein in the carcass were increased (P < 0.10) in pigs fed the diets at 3.2 vs. 2.9 x M. Based on TOBEC analysis, fat deposition, percentage of fat increase, and RE were increased (P < 0.09) in pigs fed at 3.2 x M. Plasma urea N concentrations were increased in pigs fed at 3.2 x M with no added phytase but were not affected when phytase was added to the diet (phytase x energy, P < 0.06). Fasting plasma glucose measured on d 28, ultrasound longissimus muscle area (LMA), and 10th-rib fat depth were increased (P < 0.08) in pigs fed phytase, but many other response variables were numerically affected by phytase addition. In Exp. 2, phytase had no effect (P > 0.10) on ADG, ADFI, gain:feed, LMA, or 10th-rib fat depth. These results suggest that phytase had small, mostly nonsignificant effects on energy availability in diets for growing pigs; however, given that phytase increased most of the response variables measured, further research on its possible effects on energy availability seems warranted.     

Phosphorus equivalency of a Citrobracter braakii phytase in broilers

A study was conducted to evaluate the effects of phytase supplementation on growth performance, phosphorus availability, and bone mineralization in broilers. Three hundred fifty Cobb × Cobb 500 slow-feathering male broilers were placed in steel battery cages into 7 treatments with 10 replications of 5 chicks each. The treatments were: a positive control (PC) diet [0.42% nonphytate phosphorus (nPP)], 4 diets containing increases in nPP from dicalcium phosphate (0.14, 0.20, 0.26, and 0.32%), and 2 phytase supplemental levels [500 and 1,000 phytase units ( FYT)/kg] on the diet having 0.14% nPP. All diets contained 0.8% calcium. Growth performance and bone data were regressed against the 4 diets having increased nPP. The equations generated were replaced by the corresponding performance obtained with 2 phytase levels to estimate their nPP bioequivalence. An overall reduction in performance and bone mineralization was observed associated with a reduction in nPP. Linear fits provided the best adjustments for all responses with the exceptions of BW gain (BWG) and feed intake (FI). Adding phytase to the 0.14% nPP diet improved growth performance and bone mineralization (P < 0.001). Average bioequivalence nPP for each phytase level was dependent on the evaluated response with lowest and highest values at 500 FYT supplementation of 0.077 and 0.145 for toe P and femur Ca, respectively, whereas lowest and highest values at 1,000 FYT of 0.143 and 0.194 for BWG and toe ash. Averaging all values for 500 and 1,000 FYT provided estimations of 0.100 and 0.166 nPP, respectively.