低钙磷饲粮中添加耐热植酸酶对黄羽肉鸡生产性能和养分利用率的影响

Effects of supplementation of heat-stable phytase in diet with lower calcium and phosphorus contents on growth performance and nutrient digestibility of yellow-feathered broilers

为确认经基因工程改造而以酵母发酵生产的植酸酶添加在饲粮中对肉鸡生产性能和养分利用率的影响,本文试验开展了黄羽肉仔鸡的饲养试验和代谢试验。配制3种等蛋白质等能量等钙磷比的玉米-豆粕型试验饲粮(20.5%、12.15MJ/kg和1.25),其中正对照饲粮含钙0.95%和磷0.76%,负对照饲粮含钙0.61%和磷0.50%,植酸酶组饲粮为在负对照饲粮基础上添加植酸酶(5000U/g)的饲粮(添加量100g/t)。在饲养试验中,540只2日龄粤黄雏鸡随机分为3个处理(每个处理3个重复,每个重复60只),分别饲喂3种试验饲粮,为期4周。在饲养试验结束时分别从每组每个重复栏中选择2只接近其组平均体重的仔鸡进行屠宰,取出其胫骨测定相关指标。在代谢试验中,从饲养试验结束后的正对照组中选取45只仔鸡随机分成3组(每组3个重复,每重复5只),饥饿48h后的3组分别自由采食3种试验料5d,连续收集各重复鸡的排泄物7d,分别测定试验饲粮和各排泄物烘干样的概略营养成分。试验结果表明:(1)3组间的软脚病率和死亡率差异不显著(P>0.05),植酸酶组和正对照组的耗料量分别较负对照组提高了2%(P<0.05)和12%(P<0.05),增重分别较负对照组提高了5%和13%(P<0.05),植酸酶组的耗料增重较正和负对照的均降低了3%(P<0.05);(2)植酸酶组的脱脂胫骨灰分率、含钙率和含磷率均与正对照组的差异不显著(P>0.05),但都显著高于负对照(P<0.05),分别提高了19%、23%和27%;(3)植酸酶饲粮的表观代谢能、氮存留率、钙表观消化率和磷表观消化率均与正对照组差异不显著(P>0.05),但分别比负对照组提高了1%、5%、29%(P<0.05)和12%。这表明,耐热植酸酶在低钙磷饲粮中添加可提高饲粮钙、磷、氮的利用率、耗料量和饲料转化率,从而提高黄羽肉鸡的生产性能。

To study the feeding effects of a heat-stable phytase expressed by a gene-engineered yeast on the performance and nutrient utilization of yellow-feathered broilers,a feeding experiment and a metabolism trial were carried out using 3 experimental corn-soybean diets.The 3 diets were isonitrogenous and isocaloric （20.5 %, 12.15 MJ/kg）with the same calcium-phosphorus ratio （1.25 ）.The positive control diet（PC）contained 0.95 % of calcium and 0.76 % of phosphorns,the negative control diet （NC） 0.61% of calcium and 0.50 % of phosphorus,and the the phytase diet （PH）was the NC supplemented with phytase 5000 U/g at 100 g/t.In feeding experiment,540 2-day-old yellow-feathered chicks were randomly assigned to 3 groups with 3 replicates of 60 chicks each,fed the 3 diets respectively,and supplied with water ad libitum for 4 weeks.At the end of the feeding experiment,2 chicks were selected from each replication of each treatment group and slaughtered for chemical analysis of chick tibia.In the metabolism trial ,45 chicks selected from the PC group at the end of feeding experiment were randomly assigned to 3 groups with 3 replicates of 5 chicks each.The 3 groups were fasted for 48 h and fed the 3 diets respectively for 5 d,with their excreta collected for 5 d and further 48 h and air-dried for chemical analysis respectively.The results of the experiments showed that： （1）there was no significant difference among the 3 groups in tibial dyschondroplasa （TD）and mortality （P 〉 0.05）, the feed intakes of PH and PC were higher than that of NC by 2 %（P 〈 0.05）and 12 %（P 〈 0.05）respectively,and their body weight gain higher than that of NC by 5 % and 13 %（P 〈 0.05）respectively,but the feed-gain ratio of PH lower than that of PC or NC by 3 %（P 〈 0.05）; （2）the percentage of ash, calcium and phosphorus of defatted tibia of the PH group were not significantly different from those of PCrespectively （P 〉 0.05） ,but significantly higher than those of NC by 19 %,23 % and 27 % respectively; （3）the AME,nitrogen retention,apparent digestibilityies of Ca and P of PH did not differ from those of PC respectively,but higher than those of NC by 1% ,5 % ,29 %（P 〈 0.05）and 12 % respectively.h could be concluded that the heat-stable phytase supplemented in low-phosphorus and low-calcium diet could improve the utilization of Ca, P and nitrogen, and increase feed intake,thus improve feed conversion rate and performance of yellow-feathered broilers.