本试验旨在研究低蛋白质饲粮对罗曼粉蛋鸡产蛋后期生产性能、蛋品质、氨基酸(AA)代谢率及排泄参数的影响.选取3 024只健康、产蛋率相近的61周龄罗曼粉蛋鸡,随机分为4组,每组6个重复,每个重复126只.采用玉米-豆粕型饲粮,对照组饲粮粗蛋白质(CP)水平为17.3%,3个低蛋白质组饲粮CP水平分别为16.4%(LCP1组)、15.3%(LCP2组)和13.2%(LCP3组),所有组别饲粮赖氨酸(Lys)、含硫氨基酸(TSAA)和苏氨酸(Thr)水平均保持一致.预试期1周,正试期8周.正试期结束后每重复随机挑选2只鸡单独放置在代谢笼中,采用全收粪法进行代谢试验,包括3 d预试期和4 d收粪期.结果表明:1)与对照组相比,低蛋白质组产蛋率和料蛋比均无显著差异(P>0.05),平均蛋重均显著降低(P<0.05);LCP3组日产蛋量和平均日采食量(ADFI)显著降低(P<0.05).2)与对照组相比,低蛋白质组蛋白高度、哈氏单位和蛋壳强度均无显著差异(P>0.05);LCP3组第4周蛋壳厚度显著提高(P<0.05),各组间第8周蛋壳厚度均无显著差异(P>0.05).3)与对照组相比,LCP3组血浆总蛋白(TP)含量显著提高(P<0.05);低蛋白质组血浆白蛋白(ALB)和球蛋白(GLB)含量均无显著差异(P>0.05),血浆尿酸(UA)含量显著降低(P<0.05).4)与对照组相比,LCP1组和LCP2组Lys、蛋氨酸(Met)和Thr代谢率显著提高(P<0.05),但LCP3组CP、Lys、Met和Thr代谢率均无显著差异(P>0.05).5)与对照组相比,低蛋白质组平均日粪氮排泄量均显著降低(P<0.05),LCP3组粪便CP、UA和尿素氮(UN)含量显著降低(P<0.05).综上所述,在平衡饲粮Lys、TSAA和Thr水平的前提下,罗曼粉蛋鸡产蛋后期(62~70周龄)饲粮CP水平降低至15.3%对其生产性能和蛋品质无显著影响,同时可提高CP和AA代谢率,降低粪氮排泄量.
This experiment was conducted to study the effects of low protein diet on performance,egg quality,amino acid metabolic rates and excretion parameters of Lohmann Pink laying hens during late laying period.A total of 3 024 healthy 61-week-old Lohmann Pink laying hens with similar laying rate were randomly divided into 4 groups with 6 replicates per group and 126 hens per replicate.The control group was formulated with 17.3%crude protein(CP)level in a corn-soybean type diet,and the other three low protein groups were for-mulated with 16.4%(LCP1 group),15.3%(LCP2 group)and 13.2%(LCP3 group)CP levels,respective-ly.All groups had the same levels of lysine(Lys),sulfur-containing amino acid(TSAA)and threonine(Thr)in diets.The experiment lasted for 8 weeks with 1-week adaptation.After the experiment,two hens in each replicate were randomly selected and placed in a metabolic cage,and the metabolic experiment was car-ried out by total fecal collection method,including a 3-day pre-test period and a 4-day fecal collection period.The results showed as follows:1)compared with the control group,the laying rate and feed to egg ratio in low protein groups were no significant differences(P<0.05),and the average egg weight was significantly de-creased(P<0.05);the daily egg mass and average daily feed intake(ADFI)in LCP3 group were significant-ly decreased(P<0.05).2)Compared with the control group,the albumen height,Haugh unit and eggshell strength in low protein groups were no significant differences(P<0.05);the eggshell thickness at week 4 in LCP3 group was significantly increased(P<0.05),but there were no significant differences in eggshell thick-ness at week 8 among all groups(P>0.05).3)Compared with the control group,the plasma total protein content in LCP3 group was significantly increased(P<0.05);the plasma contents of albumin(ALB)and globulin(GLB)in low protein groups were no significant differences(P>0.05),and the plasma uric acid(UA)content was significantly decreased(P<0.05).4)Compared with the control group,the metabolic rates of Lys,methionine(Met)and Thr in LCP1 and LCP2 groups were significantly increased(P<0.05),and the metabolic rates of CP,Lys,Met and Thr in LCP3 group had no significant differences(P>0.05).5)Compared with the control group,the average daily nitrogen excretion in low protein groups was significantly decreased(P<0.05),and the fecal contents of CP,UA and urea nitrogen(UN)in LCP3 group were signifi-cantly decreased(P<0.05).In conclusion,under the premise of balancing dietary levels of Lys,TSAA and Thr levels,dietary CP level decreasing to 15.3%for Lohmann Pink laying hens during the late laying period(62 to 70 weeks of age)has no significant effects on performance and egg quality,but can improve the meta-bolic rates of CP and AA,and reduce fecal nitrogen excretion.[Chinese Journal of Animal Nutrition,2023,35(12):7714-7723]