植酸酶对肉鸡生产性能与胴体品质的影响

试验选取1日龄AA肉鸡600只,随机分为6个处理组,每个处理组5个重复。试验分两阶段饲养,分别参照NRC(1994)饲养标准配制玉米—豆粕型基础日粮,1～3周龄和4～6周龄正、负对照组调整有效磷水平分别为0.43%、0.23%和0.34%、0.14%,试验组(3、4、5、6组)分别在负对照组日粮中添加250、500、750、1000U/kg植酸酶。试验结果表明,500、750U/kg加酶组较负对照组显著提高了肉鸡日增重(P<0.05),比正对照组也提高了3.41%、3.19%;添加植酸酶对21日龄肉鸡屠宰性能及肉品质有所降低,不影响42日龄屠宰性能与肉品质。     

玉米-杂粕型日粮中添加不同植酸酶对蛋鸡生产性能和蛋品质及钙磷代谢的影响

选取720只24周龄海兰褐蛋鸡,随机分为8个处理,每个处理6个重复,每个重复15只鸡。8个处理分别为正对照组(PC)饲喂有效磷为0.36%的正常基础日粮,负对照组(NC)饲喂有效磷为0.16%的低磷日粮,其余试验组是在NC组日粮基础上分别添加两种植酸酶A或B各125、250、500 U/kg。其中植酸酶A是从大肠杆菌中提取,植酸酶B是从里氏木霉中提取。试验期为12周。结果表明:与PC组比较,NC和B500组产蛋率、平均蛋重和日采食量显著降低(P0.05),其他各添加植酸酶组恢复到PC组水平,各添加植酸酶组料蛋比和蛋品质无显著变化(P0.05);与PC组相比,NC组胫骨灰分、胫骨磷和血浆磷含量显著降低(P0.05),添加2种植酸酶组(除B500组外)恢复到PC组水平,B500组血浆磷含量显著低于PC组(P0.05),各试验组胫骨钙含量和血浆钙含量与PC组无显著差异(P0.05)。结果提示,低磷玉米-杂粕型日粮中添加2种植酸酶都能够缓解低磷引起的负效应,但2种植酸酶的最佳添加量不同,本试验条件下日粮中添加125 U/kg的植酸酶B或250 U/kg的植酸酶A都能满足蛋鸡对无机磷的需求。     

新型耐热植酸酶对肉仔鸡营养物质表观消化率及胫骨灰分含量的影响

试验在低磷日粮中分别添加普通植酸酶与耐高温植酸酶,研究两种植酸酶对肉仔鸡营养物质表观消化率及胫骨灰分含量的影响。选用4 800只1日龄AA肉仔鸡,随机分为6个处理,每个处理设5个重复。试验分2期进行,1~3周和4~6周。对照组饲喂基础日粮,处理1组降低基础日粮的磷水平,处理2组与处理3组分别在其基础上添加普通植酸酶500、2 000 U/kg,处理4组和处理5组分别添加耐高温植酸酶250、500 U/kg。结果表明:①当降低基础日粮中磷添加水平时,降低了磷的表观消化率;在此基础上添加500~2 000 U/kg普通植酸酶或250~500 U/kg耐热植酸酶,显著提高了磷的表观消化率,且超过了对照组,其中以250~500 U/kg耐热植酸酶与2 000 U/kg普通植酸酶效果理想。降低磷添加水平或添加不同来源植酸酶对粗蛋白质和钙的表观消化率基本没有影响;②当降低基础日粮中磷添加水平时,显著降低了胫骨灰分和磷的含量(P<0.05),同时钙含量呈降低趋势(P>0.05);在此基础上添加500~2 000 U/kg普通植酸酶或250~500 U/kg耐热植酸酶,胫骨灰分和钙、磷的含量恢复到或超出对照组水平。     

耐高温植酸酶用于颗粒饲料对肉鸡生产性能及钙、磷利用率的影响

试验旨在研究肉仔鸡低磷日粮颗粒饲料中添加耐高温植酸酶对肉鸡生产性能及钙、磷利用率的影响。选取1日龄AA+肉仔鸡,随机分为6个处理,分别饲喂处理1(正对照,正常磷水平)、处理2(负对照,低于正常磷水平)、处理3(负对照+500U植酸酶)、处理4(高磷替代+500U植酸酶)、处理5(负对照+1000U植酸酶)和处理6(高磷替代+1000U植酸酶)试验日粮。试验结果表明:在制粒饲料中添加耐高温植酸酶是可行的。在相同有效磷水平下,随着植酸酶添加水平的提高,出栏体重有增加的趋势;在相同植酸酶添加量的条件下,随着有效磷替代水平的提高,出栏体重有降低的趋势。添加植酸酶有增加胫骨灰分和磷含量的趋势。在正常替代水平下,植酸酶的添加量以500～1000U/kg为宜。在本试验条件下,日粮添加500～1000U/kg植酸酶的情况下,进行磷酸氢钙的高水平替代也是可行的。     

高剂量植酸酶对肉鸡生长性能和消化率的影响

文章旨在研究植酸酶对1~42日龄肉鸡生长发育的影响。采用完全随机试验设计,试验共分为5组,每组6个重复,每个重复24只鸡,各组分别为阳性对照组、负对照、负对照日粮+1000、2000和3000IU/kg植酸酶,试验结束后测定各组对骨功能、骨质量和血液矿物质的影响。随着日粮植酸酶添加水平的升高,显著改善了1~21d肉鸡日增重、采食量和料比(P<0.05),而1~42d肉鸡生长性能表现为显著二次曲线效应(P<0.05),其中负对照组肉鸡日增重和采食量最低(P<0.05),料比最高(P<0.05)。对照组较负对照组显著提高了42d肉鸡胫骨干物质含量(P<0.05)。随着植酸酶添加水平的升高,21d肉鸡血钙浓度表现为显著线性降低(P<0.05),而血磷浓度先升高后降低,负对照日粮+1000IU/kg植酸酶组最高(P<0.05)。42d肉鸡血磷浓度随日粮植酸酶水平的升高表现为二次曲线效应。对照组和负对照组较处理组显著提高了42d肉鸡血钙浓度(P<0.05)。与对照和负对照组相比,负对照添加植酸酶组显著降低了矿物质回肠表观消化系数(P<0.05),而负对照组+3000IU/kg植酸酶较对照组显著降低了能量回肠表观消化系数(P<0.05)。植酸酶在回归分析的基础上提高了肉鸡生长性能,添加高剂量植酸酶3000IU/kg显著提高21d肉鸡日增重。试验为期42d,日粮添加2000IU/kg植酸酶对肉鸡的增重和饲料转化率效果较好。     

南方高温环境下植酸酶对杜长大猪生产性能和钙、磷、蛋白质利用率的影响

本研究选用60头4周龄杜长大断奶仔猪(7.33±0.45kg),评价在我国南方夏季高温环境下植酸酶对高生产性能猪的生物学功效.试验设5个处理组,每个处理组设6个重复(每重复2头猪),饲喂玉米-米糠-豆粕型饲粮.在低磷水平的饲粮(负对照组)中,分别添加250PTU/kg、500PTU/kg、750PTU/kg植酸酶和0.15%无机磷(正对照组),组成5种不同的试验饲粮.试验结果表明植酸酶的添加,显著提高了断奶到育成阶段猪的日增重和采食量;改善了血清无机磷、钙浓度;提高了饲粮中磷、钙的消化率,降低了粪中磷的排放量.试验结果表明,植酸酶可以部分替代断奶到育成阶段猪饲粮中无机磷,并减轻磷对环境的污染.本研究根据植酸酶和无机磷对猪生产性能、血清相关生化指标和饲粮中磷、钙的消化率反应的比较推断,500～750PTU/kg植酸酶即可替代0.15%饲料无机磷.     

植酸酶对肉仔鸡生产性能及钙、磷利用率的影响

试验研究肉仔鸡低有效磷日粮中添加植酸酶对生产性能及钙、磷利用率的影响。选取960只1日龄AA肉仔鸡,随机分为8个处理,每个处理6个重复,每个重复20只仔鸡（公母各半）,试验分为前期（1-21 d）和后期（22-42 d）两个阶段。第I组为正对照组PC（试验基础日粮,前、后期有效磷水平分别为0.47%、0.43%）,第II组为负对照组NC（前、后期分别降低有效磷水平0.06%、0.1%）,第Ⅲ-第Ⅴ组分别为NC＋500 U/kg包衣植酸酶、NC＋1 000U/kg包衣植酸酶,NC＋1 0000 U/kg包衣植酸酶,第Ⅵ组为NC＋500 U/kg粉状植酸酶,第Ⅶ组为NC＋500 U/kg微丸植酸酶,第Ⅷ组为NC＋500 U/kg进口粉状植酸酶。结果表明：（1）除Ⅶ组后期采食量较正对照组有显著提高外,各处理组平均日采食量、平均日增重差异均不显著（P〉0.05）,Ⅶ组前期料重比较正、负对照组均有显著降低（P〈0.05）,且正对照组全期料重比显著低于负对照组（P〈0.05）,所有酶处理组后期和全期料重比均较负对照组有所降低,但差异不显著（P〉0.05）。（2）Ⅵ组前期DM和EE消化率显著高于正对照组,除Ⅲ组外所有酶处理组前期能量和P消化率均显著高于正、负对照组（P〈0.05）;Ⅶ和Ⅷ组后期DM消化率显著高于正对照组（P〈0.05）,Ⅳ组后期EE消化率显著高于正、负对照组,除Ⅲ组外所有酶处理组以及负对照组后期P消化率均显著高于正对照组（P〈0.05）。（3）Ⅲ组前期胫骨长度显著高于正、负对照组,Ⅳ和Ⅴ组及负对照组后期胫骨长度均显著大于正对照组（P〈0.05）;Ⅴ组后期胫骨Ca含量显著高于正、负对照组,所有酶处理组前、后期胫骨P含量均较负对照组有所升高,但差异不显著（P〉0.05）。试验结果表明低有效磷日粮中添加植酸酶对饲料利用率有一定的改善作用,有效提高饲料代谢能以及磷的消化和沉积。     

南方高温环境下植酸酶对杜长大猪生产性能和钙、磷、蛋白质利用率的影响

本研究选用60头4周龄杜长大断奶仔猪(7.33±0.45kg),评价在我国南方夏季高温环境下植酸酶对高生产性能猪的生物学功效。试验设5个处理组,每个处理组设6个重复(每重复2头猪),饲喂玉米-米糠-豆粕型饲粮。在低磷水平的饲粮(负对照组)中,分别添加250PTU/kg、500PTU/kg、750PTU/kg植酸酶和0.15%无机磷(正对照组),组成5种不同的试验饲粮。试验结果表明:植酸酶的添加,显著提高了断奶到育成阶段猪的日增重和采食量;改善了血清无机磷、钙浓度;提高了饲粮中磷、钙的消化率,降低了粪中磷的排放量。试验结果表明,植酸酶可以部分替代断奶到育成阶段猪饲粮中无机磷,并减轻磷对环境的污染。本研究根据植酸酶和无机磷对猪生产性能、血清相关生化指标和饲粮中磷、钙的消化率反应的比较推断,500～750PTU/kg植酸酶即可替代0.15%饲料无机磷。     

植酸酶对肉仔鸡生产性能及钙、磷利用率的影响

试验研究肉仔鸡低有效磷日粮中添加植酸酶对生产性能及钙、磷利用率的影响。选取960只1日龄AA肉仔鸡,随机分为8个处理,每个处理6个重复,每个重复20只仔鸡（公母各半）,试验分为前期（1-21 d）和后期（22-42 d）两个阶段。第I组为正对照组PC（试验基础日粮,前、后期有效磷水平分别为0.47%、0.43%）,第II组为负对照组NC（前、后期分别降低有效磷水平0.06%、0.1%）,第Ⅲ-第Ⅴ组分别为NC＋500 U/kg包衣植酸酶、NC＋1 000U/kg包衣植酸酶,NC＋1 0000 U/kg包衣植酸酶,第Ⅵ组为NC＋500 U/kg粉状植酸酶,第Ⅶ组为NC＋500 U/kg微丸植酸酶,第Ⅷ组为NC＋500 U/kg进口粉状植酸酶。结果表明：（1）除Ⅶ组后期采食量较正对照组有显著提高外,各处理组平均日采食量、平均日增重差异均不显著（P〉0.05）,Ⅶ组前期料重比较正、负对照组均有显著降低（P〈0.05）,且正对照组全期料重比显著低于负对照组（P〈0.05）,所有酶处理组后期和全期料重比均较负对照组有所降低,但差异不显著（P〉0.05）。（2）Ⅵ组前期DM和EE消化率显著高于正对照组,除Ⅲ组外所有酶处理组前期能量和P消化率均显著高于正、负对照组（P〈0.05）;Ⅶ和Ⅷ组后期DM消化率显著高于正对照组（P〈0.05）,Ⅳ组后期EE消化率显著高于正、负对照组,除Ⅲ组外所有酶处理组以及负对照组后期P消化率均显著高于正对照组（P〈0.05）。（3）Ⅲ组前期胫骨长度显著高于正、负对照组,Ⅳ和Ⅴ组及负对照组后期胫骨长度均显著大于正对照组（P〈0.05）;Ⅴ组后期胫骨Ca含量显著高于正、负对照组,所有酶处理组前、后期胫骨P含量均较负对照组有所升高,但差异不显著（P〉0.05）。试验结果表明低有效磷日粮中添加植酸酶对饲料利用率有一定的改善作用,有效提高饲料代谢能以及磷的消化和沉积。     

25-OH-VD_3和植酸酶对肉鸡生长性能及血清生化指标的影响

研究旨在探讨植酸酶与25-OH-VD3配合使用对肉鸡生长性能及血清生化指标的影响。试验选取岭南黄羽肉鸡780只,集中育雏7日之后,随机分为5个处理,每个处理6个重复,每重复26只。5个处理分别为:正对照组、负对照组、负对照组+500 U/kg植酸酶、负对照组+70μg/kg 25-OH-VD3、负对照组+500 U/kg植酸酶+70μg/kg 25-OH-VD3。其中负对照组钙、磷水平分别比正对照组降低0.20%、0.12%。饲养试验分为三个阶段:8~21 d、22~36 d、37~58 d。统计各阶段肉鸡的始重、末重、平均日增重、平均日采食量和耗料增重比等生产性能。21、36、58 d时,每个重复挑取2只试验鸡屠宰,采集血清用于测定血钙、血磷和血清碱性磷酸酶(ALP)。结果表明:添加500 U/kg的植酸酶,其各期平均日增重、料重比都好于负对照组(P>0.05);在低钙、磷水平肉鸡日粮添加70μg/kg 25-OH-VD3对不同阶段的肉鸡生产性能均有一定程度的提高,尤其是22～36日龄肉鸡的平均日增重显著高于正、负对照组(P<0.05);但是,在低钙磷日粮配合使用植酸酶和25-OH-VD3未呈现出加和效应。     

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.     

小麦日粮中木聚糖酶和植酸酶对肉仔鸡生长和养分消化率的影响

432只艾维因肉仔鸡用于研究小麦基础日粮中添加木聚糖酶(320FXU/kg)或添加750U/kg植酸酶降低日粮中0.08％的非植酸磷后,对生长性能、日粮表观代谢能、粗蛋白和植酸磷表观消化率的影响。试验结果表明:无论是单一添加木聚糖酶或植酸酶,还是同时添加这两种酶,都能提高1-6周龄肉仔鸡的增重和饲料转化率,降低死亡率。添加木聚糖酶可提高肉仔鸡小麦日粮的表观代谢能2.14％,增加氮的存留量2.58％。750U/kg的植酸酶完全可以降低肉仔鸡小麦日粮中0.08％非植酸磷。添加植酸酶的处理组可提高植酸磷的表观消化率43.25％,减少植酸磷排泄量55.0％。植酸酶和木聚糖酶对全期饲料转化率和植酸磷的表观消化率表现有明显的正互作效应(P<0.05)。     

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.     

Effects of an experimental phytase on performance, egg quality, tibia ash content and phosphorus bioavailability in laying hens fed on maize- or barley-based diets

A 24-week performance trial was conducted to evaluate the efficacy of an experimental phytase on performance, egg quality, tibia ash content and phosphorus excretion in laying hens fed on either a maize- or a barley-based diet. At the end of the trial, an ileal absorption assay was conducted in order to determine the influence of phytase supplementation on the apparent absorption of calcium and total phosphorus (P). Each experimental diet was formulated either as a positive control containing 3.2 g/kg non-phytate phosphorus (NPP), with the addition of dicalcium phosphate (DCP), or as a low P one, without DCP addition. Both low P diets (containing 1.3 or 1.1 g/kg NPP) were supplemented with microbial phytase at 0, 150, 300 and 450 U/kg. The birds were housed in cages, allocating two hens per cage as the experimental unit. Each of 10 dietary treatments was assigned to 16 replicates. Low dietary NPP (below 1.3 g/kg) was not able to support optimum performance of hens during the laying cycle (from 22 to 46 weeks of age), either in maize or barley diets. Rate of lay, daily egg mass output, feed consumption, tibia ash percentage and weight gain were reduced in hens fed low NPP diets. The adverse effects of a low P diet were more severe in hens on a maize diet than in those on a barley diet. Low dietary NPP reduced egg production, weight gain, feed consumption and tibia ash content and microbial phytase supplementation improved these parameters. Hens given low NPP diets supplemented with phytase performed as well as the hens on positive control diets containing 3.2 g/kg of NPP. A 49% reduction of excreta P content was achieved by feeding hens on low NPP diets supplemented with phytase, without compromising performance. Phytase addition to low NPP diets increased total phosphorus absorption at the ileal level, from 0.25 to 0.51 in the maize diet and from 0.34 to 0.58 in the barley diet. Phosphorus absorption increased linearly with increasing levels of dietary phytase. Mean phosphorus absorption was higher in barley diets than in maize diets (0.49 vs 0.39).     

Effects of a novel bacterial phytase expressed in Aspergillus Oryzae on digestibility of calcium and phosphorus in diets fed to weanling or growing pigs

In 2 experiments, 48 weanling (initial BW: 13.5 ± 2.4 kg, Exp. 1) and 24 growing pigs (initial BW: 36.2 ± 4.0 kg, Exp. 2) were used to determine effects of a novel bacterial 6-phytase expressed in Aspergillus oryzae on the apparent total tract digestibility (ATTD) of phosphorus and calcium in corn-soybean meal diets fed to weanling and growing pigs. In Exp. 1 and 2, pigs were randomly allotted to 6 dietary treatments using a randomized complete block design and a balanced 2 period changeover design, respectively. In both experiments, 6 diets were formulated. The positive control diet was a corn-soybean meal diet with added inorganic phosphorus (Exp. 1: 0.42 and 0.86% standardized total tract digestible phosphorus and total calcium, respectively; Exp. 2: 0.32 and 0.79% standardized total tract digestible phosphorus and total calcium, respectively). A negative control diet and 4 diets with the novel phytase (Ronozyme HiPhos, DSM Nutritional Products Inc., Parsippany, NJ) added to the negative control diet at levels of 500, 1,000, 2,000, and 4,000 phytase units (FYT)/kg were also formulated. In Exp. 1, the ATTD of phosphorus was greater (P < 0.01) for the positive control diet (60.5%) than for the negative control diet (40.5%), but increased (linear and quadratic, P < 0.01) as phytase was added to the negative control diet (40.5% vs. 61.6%, 65.1%, 68.7%, and 68.0%). The breakpoint for the ATTD of phosphorus (68.4%) was reached at a phytase inclusion level of 1,016 FYT/kg. In Exp. 2, the ATTD of phosphorus was greater (P < 0.01) for the positive control diet (59.4%) than for the negative control diet (39.8%) and increased (linear and quadratic, P < 0.01) as phytase was added to the negative control diet (39.8% vs. 58.1%, 65.4%, 69.1%, and 72.8%). The breakpoint for the ATTD of phosphorus (69.1%) was reached at a phytase inclusion level of 801 FYT/kg. In conclusion, the novel bacterial 6-phytase improved the ATTD of phosphorus and calcium in both weanling and growing pigs. The optimum level of inclusion for this phytase is 800 to 1,000 FYT/kg of complete feed to maximize ATTD of phosphorus and calcium in weanling and growing pigs.     

Non‐phytate phosphorus requirements and efficacy of a genetically engineered yeast phytase in male lingnan yellow broilers from 1 to 21 days of age

This experiment was conducted to investigate the requirement of non‐phytate phosphorus (nPP) and efficacy of a genetically engineered yeast phytase in performance and tibia characteristics by male Lingnan Yellow broilers from 1 to 21 days of age. A total of 2640 1‐day‐old male chicks were randomly allotted to one of 11 dietary treatments, which consisted of six replicate floor pens with 40 birds per pen. All treatments had the same levels of all nutrients except for phosphorus and phytase. The control group (treatment 1) was fed the basal diet without dicalcium phosphate or phytase supplementation. Dietary concentrations of nPP were 0.11%, 0.19%, 0.27%, 0.35%, 0.43%, 0.51% and 0.59% respectively for treatments 1, 2, 3, 4, 5, 6 and 7, through addition of dicalcium phosphate (chemistry grade) to the basal diet. Diets 8–11 were supplemented with a genetically engineered yeast phytase 250, 500, 750 U/kg and a commercial phytase product 500 U/kg in basal diet respectively. The results showed that 0.46% and 0.51% nPP were required for maximum body‐weight gain and optimum tibia development indicators respectively. However, 0.59% nPP had a negative effect on bird growth. The equivalency value of the genetically engineered yeast phytase was estimated to be 874 U/kg to liberate 0.1% nPP.     

Limiting order of amino acids and the effects of phytase on protein quality in corn gluten meal fed to young chicks

An amino acid deletion assay, a protein efficiency ratio (PER) assay, and a slope-ratio growth assay were used to establish the limiting order of AA, and to determine the effects of microbial phytase on protein utilization in corn gluten meal (CGM) fed to chicks during the period of 8 to 21 d posthatching. In Assay 1, a 12% CP CGM diet was fortified with AA to fulfill the digestible AA ideal profile (only Phe + Tyr, Leu, and Pro exceeded requirements) for young chicks. Amino acids were then individually deleted, and all diets were fortified to 23% CP, with Glu varying as necessary. A Met-fortified 23% CP corn-soybean meal diet served as a positive control. No weight gain or feed efficiency differences were observed between the fully fortified CGM basal diet and the corn-soybean meal positive-control diet. The limiting order of AA established in CGM was 1) Lys, 2) Trp, 3) Arg, 4) Thr, 5) Val, 6) Ile, 7) His, 8) cystine, and 9) Met. In Assay 2, diets with 10% CP furnished by CGM or casein were fed in the presence and absence of 1,200 U/kg phytase. A protein source x phytase interaction (P < 0.05) was observed for weight gain, gain:feed, and PER, indicating positive responses to phytase when casein was fed but negative responses to phytase when CGM was fed. In Assay 3, graded levels of protein (8, 16, and 24% CP) furnished by CGM were fed in the presence and absence of 1,200 U/kg phytase. Weight gain and gain:feed increased linearly (P < 0.05) as a function of protein intake, but phytase supplementation had no effect on weight gain or gain:feed slopes. These results indicate that 1,200 U/kg phytase did not increase either CP or AA utilization in CGM for young chicks.     

Effects of microbial phytase, produced by solid-state fermentation, on the performance and nutrient utilisation of broilers fed maize- and wheat-based diets

1. The influence of a microbial phytase on the performance, toe ash contents and nutrient utilisation of male broilers fed diets based on maize and wheat was investigated. The experiment was conducted as 2 x 2 x 2 factorial arrangement of treatments. Within the factorial, two diet types (maize-soy or wheat-soy) containing two levels of non-phytate phosphorus (3.0 or 4.5 g/kg) were evaluated and each level of non-phytate phosphorus was supplemented with 0 or 500 PU phytase/kg diet. Each of the 8 dietary treatments were fed to 6 pens of 8 birds from d 1 to 21 post-hatching. 2. Main effects of diet type and phytase were observed for all parameters. Main effect of non-phytate phosphorus was significant only for feed/gain and toe ash contents. Phytase addition improved weight gains irrespective of diet type or non-phytate phosphorus level, but the magnitude of improvement in the phosphorus-deficient wheat-soy diet was greater, resulting in a diet type x non-phytate phosphorus interaction. Responses in toe ash contents were noted only in phosphorus-deficient diets, as indicated by a non-phytate phosphorus x phytase interaction. 3. Phytase addition improved apparent metabolisable energy values of wheat-based diets, but had little effect on the apparent metabolisable energy of maize-based diets as shown by a diet type x phytase interaction. The apparent metabolisable energy was not influenced by dietary non-phytate P. 4. Phytase improved ileal nitrogen digestibility in both diet types, but the responses to added phytase tended to be higher in wheat-based diets, as shown by a diet type x phytase interaction. 5. Increasing the dietary non-phytate phosphorus level reduced phosphorus digestibility and increased excreta phosphorus content. Addition of phytase improved phosphorus digestibility, but the increments were higher in low phosphorus diets resulting in a non-phytate phosphorus x phytase interaction. Phytase addition tended to lower the excreta phosphorus content, but the effects were greater in birds fed low phosphorus diets, as shown by a non-phytate phosphorus x phytase interaction.     

Effects of different dietary phytase activities on the concentration of antioxidants in the liver of growing broilers

One‐hundred and fifty male chickens were used to evaluate the effects of different activities (0, 250, 500, 12 500 FTU/kg) of phytase on their performance and antioxidant concentration in the liver. The chicks were housed in 30 cages and were allocated to six replicates of five dietary treatments. All diets were formulated to be adequate in energy and protein (12.90 MJ/kg metabolizable energy, 214 g/kg crude protein), however, the negative control (NC) was lower in available P compared with the positive control (PC) (2.5 vs. 4.5 g/kg diet). The other three diets were the NC supplemented with phytase at 250, 500 and 12 500 FTU/kg (NC + 250, NC + 500 and NC + 12 500 FTU respectively). The concentration of antioxidants in the liver of the birds was determined using HPLC at 21 days of age. Low P diets (NC) reduced weight gain, however, supplementation with phytase improved weight gain to the extent that it was better than the PC at the 12 500 FTU treatment (p < 0.05). Feed conversion ratio was also improved by the high level of phytase supplement more than other treatments (p < 0.05). Feed consumption was not affected either by dietary phosphorus concentration or by different phytase supplementation. The antioxidant data showed that the unsupplemented diet with low phosphorus (NC) decreased the concentration of coenzyme Q₁₀ and retinol‐linoleate in the liver compared with that of birds on the adequate phosphorus treatment (PC). Phytase supplementation, especially at the higher doses (500 and 12 500 FTU) increased the level of coenzyme Q₁₀ to the same level as the PC treatment. In addition, the highest dose (12 500 FTU) of phytase increased retinol concentration in the liver of chickens compared with those on the NC treatment. The highest inclusion level of phytase increased the α‐tocopherol level in the liver compared with the lower levels of phytase (NC + 250 and NC + 500 FTU).