【作者】 张林；

【导师】 姚军虎；

【作者基本信息】 西北农林科技大学 ， 动物营养与饲料科学， 2012， 博士

【摘要】 禽类的眼睛对光特别敏感，光照是影响家禽生产力表现的主要环境因素之一。选择合适的人工光照制度，是现代家禽养殖业用于提高家禽生产性能的重要方式。快大型白羽肉鸡的孵化期为21天，几乎占其生命周期（按42日上市）的1/3，因此在孵化期间采取光照措施调控其肌肉生长对家禽生产具有重要意义。本研究分4个试验，采用分光光度法、放射免疫法、酶联免疫反应法、免疫组化学法、实时荧光定量PCR等方法研究孵化期间单色光刺激对肉仔鸡肌肉生长、血液激素水平、肌肉组分与品质、胸肌纤维形态、卫星细胞有丝分裂活性、生长因子及成肌调控因子mRNA表达的影响，探讨孵化期单色光照调控肉仔鸡肌肉生长的可能机理，以期为肉鸡孵化场确定合理的孵化工艺提供理论依据。试验一孵化期单色光刺激对肉仔鸡胸肉生长、胸肌成分和肉品质的影响本试验采用LED灯为光源，探讨孵化期单色光刺激对肉仔鸡生产性能、胸肌化学成分及其肉品质的影响。1320枚AA鸡商品代受精蛋随机分配到蓝光组（480nm）、绿光组（560nm）和黑暗组（对照）3种光照处理的孵化器中，采用持续光照，强度为蛋壳水平位置处15lx。肉仔鸡出壳后，从每个处理各选取120只公雏，每个处理6个重复，每个重复20只鸡。自由采食和饮水，统一采用白炽灯补光，强度30lx，光照时间23L:1D。结果显示，各处理种蛋孵化率、肉仔鸡初生重及生长期采食量均无显著差异（P>0.05）。与黑暗组或蓝光组相比，绿光刺激可显著提高肉仔鸡21d、35d和42d体重和采食量（P<0.05）。42d时，绿光组肉仔鸡胸肌重和胸肌率均最高，分别较黑暗组提高50.39g和11.78%，较蓝光组提高54.07g和12.70%（P <0.05）。绿光组0³5d和0⁴2d的饲料转化率分别为1.66和1.80，显著优于黑暗组（1.73和1.88，P <0.05）。各处理组肉仔鸡42d胸肌水分、粗蛋白、粗脂肪和粗灰分含量差异均不显著（P>0.05）。孵化期绿光或蓝光刺激均不影响肉仔鸡42d胸肌pH值、滴水损失、剪切力值、45min肉色（L^*、a^*和b^*值）及24h肉色a^*和b^*值（P>0.05），但绿光组蒸煮损失（P=0.08）和24h肉色L^*值（P=0.09）均有升高的趋势。本研究表明，孵化期绿光刺激可显著提高肉仔鸡生长期体重和胸肌产量，改善饲料转化率，但不影响胸肌化学成分和肉品质。试验二孵化期单色绿光刺激对肉仔鸡孵化后期和生长期血液激素水平的影响本试验通过检测孵化后期及生长期血浆中生长激素（GH）、胰岛素样生长因子I（IGF-I）、甲状腺素（T₄）、三碘甲腺原氨酸（T₃）和睾酮含量的变化，探讨孵化期单色绿光刺激对肉仔鸡促生长作用的神经-内分泌机制。880枚AA鸡商品代受精蛋随机分配到绿光组（560nm）和黑暗组2种光照处理的孵化器中，采用持续光照，强度为蛋壳水平位置处15lx。肉仔鸡出壳后，从每个处理各选取120只公雏，每个处理6个重复，每个重复20只鸡。按预先设计的采血时间点从孵化期第15天（E15）到生长期第42天（H42）采集血样，制备血浆。结果显示，与黑暗组相比，胚胎期绿光刺激可显著提高E19天胚胎到H5天肉仔鸡血浆中GH水平（P <0.05）。绿光组胚胎期E17到E19天和生长期H3到H35天血浆中IGF-I水平均显著高于黑暗组（P <0.05）。黑暗组和绿光组胚胎期及生长期肉仔鸡各检测点血浆T3、T4和睾酮水平均无显著差异（P>0.05）。与黑暗组相比，绿光组肉仔鸡血浆T3水平在H7天（P=0.09）到H21天（P=0.06）有升高趋势。本研究表明，孵化期绿光刺激通过促进生长轴激素GH和IGF-I的分泌调控肉仔鸡胚胎发育与出雏后肌肉生长。试验三孵化期单色绿光刺激对肉仔鸡孵化后期和生长期胸肌中相关生长因子基因表达的影响本试验通过检测孵化后期及生长期胸肌中GH受体（GHR）、IGF-I、IGF-I受体（IGF-IR）和肌肉生长抑制素（MSTN）mRNA表达量的变化，探讨绿光刺激的促生长作用是否受肌肉生长因子和MSTN调控。结果显示，与黑暗组相比，孵化期绿光刺激显著上调肉仔鸡胚胎后期和生长期胸肌中GHR（E17到H21天）和MSTN（E17到E19天和H5到H7天）mRNA表达量（P <0.05）。两处理组肉仔鸡胚胎期胸肌IGF-I和IGF-IR表达量无显著差异（P>0.05），但绿光组肉仔鸡生长前期胸肌IGF-I和IGF-IR表达量均显著高于黑暗组（P <0.05）。本研究表明，孵化期绿光刺激通过促进胚胎期及生长期关键生长因子和肌肉生长抑制素表达调控肉仔鸡的胚胎发育和肌肉生长。试验四孵化期单色绿光刺激对肉仔鸡孵化后期和出雏早期卫星细胞增殖和分化的影响本试验通过检测肉仔鸡胚胎后期（E15天）和出雏早期（H7天）胸肌重、肌纤维面积、卫星细胞有丝分裂活性和成肌调控因子MyoD和MyoG mRNA的表达量，探讨孵化期单色绿光刺激对调控肉仔鸡胸肌卫星细胞增殖分化的机理。与黑暗组相比，绿光组肉仔鸡H7天的体重和胸肌产量分别显著提高14.33g和1.46g（P <0.05）。绿光刺激显著提高肉仔鸡H1天和H3天的卫星细胞有丝分裂活性，及H5和H7天胸肌纤维面积（P<0.05）。此外，绿光组肉仔鸡胸肌MyoD（E17到H3天）和MyoG（H1到H5天）mRNA表达量均显著高于黑暗组（P <0.05）。本研究表明，孵化期绿光刺激通过提高胚胎后期和出雏早期胸肌卫星细胞的增殖和分化活性，促进肉仔鸡出雏早期的肌肉生长。本研究表明孵化期单色绿光刺激增加胚胎后期和生长期促生长轴激素GH和IGF-I的分泌，上调肉仔鸡胚胎后期和出雏早期胸肌中生长因子GHR和MSTN，及成肌调节因子MyoD和MyoG mRNA的表达量，提高骨骼肌卫星细胞的有丝分裂活性，促进卫星细胞增殖与分化，最终增加生长期肉仔鸡的胸肌生长。更多还原

【Abstract】 Poultry are light sensitive species, and light had become an important environmentalfactor that influences the poultry performances. Artificial illumination has been widely usedto promote avian productive performance in modern poultry industry. The hatching period offast-growing broilers takes21days, which almost takes one third of its life span （calculatedby a42-day feeding period）. Therefore, broiler performance promoted by light stimuli duringembryogenesis might be important for poultry industry. This dissertation consists of4experiments. The effect of monochromatic light stimuli during embryogenesis on breastmuscle growth, chemical composition, meat quality, blood hormone levels, muscle fibermorphology, satellite cell mitotic activity, along with expression of growth-related factors andmyogenic regulatory factors in pectoral muscle of broilers was systematically investigated byusing the methods of absorption spectrometry, radioimmunoassay, enzyme-linkedimmunoassay, immunohistochemistry, and real time quantitative RT-PCR. These data willprovide a scientific data for poultry hatchery.Trial1focused on the effect of monochromatic light stimuli during embryogenesis onmuscular growth, chemical composition, and meat quality of breast muscle in male broilers.Fertile broiler eggs （Arbor Acres, n=1320） were preweighed and randomly assigned to oneof three treatment groups in3modified incubators:1) control group （in dark condition）,2)monochromatic green light group （560nm）, and3) monochromatic blue light group （480nm）.The monochromatic lighting systems sourced from light-emitting diode lamps and wereequalized at the intensity of15lx at eggshell level. After hatching,120male chicks from eachgroup were placed in6replicates with20birds each. All the birds were housed under whitelight （30lx at bird-head level） with a light schedule of23L:1D. At21,35, and42d of age,BW and breast muscle weight in the green light group were significantly increased comparedwith birds in the blue or dark groups （P <0.05）. The breast muscle weight and breast musclepercentages in birds incubated under green light were significantly elevated by50.39g （11.78%） and54.07g （12.70%） than those in dark condition or blue group at42d of marketage （P <0.05）, respectively. In the green light group, feed intake during0⁴2d was higherthan that in the other2treatment groups （P <0.05）; feed conversion ratio during0³5d and0⁴2d were lower than that in the dark condition （1.66vs.1.73during0³5d;1.80vs.1.88during0⁴2, P <0.05, respectively）. No significant differences in the contents of breastmoisture, CP, crude fat and crude ash among all groups were observed （P>0.05）. Green lightstimuli tended to increase cooking loss （P=0.08）, and L^*value of24-h meat color （P=0.09）.These results suggested that green light stimuli during embryogenesis enhanced the posthatchBW of male broilers, increased breast muscle growth, and improved the feed coversion ratio,but it did not cause any noticeable changes in breast chemical composition or overall meatquality characteristics.Trial2was aimed to investigate whether the regulation of chicken embryonic orposthatch growth by green light stimuli during incubation is associated with the changes ofexdocrine axes by measuring dynamical changes in plasma growth hormone （GH）,insulin-like growth factor-I （IGF-I）, triiodothyronine （T₃）, thyroxine （T₄）, and testosteroneconcentrations at different ages of embryogenesis and posthatching chicks. Fertile broilereggs （Arbor Acres, n=880） were preweighed and randomly assigned to1of2treatments in2modified commercial incubators:1) control group （in dark condition）, and2) monochromaticgreen light group （560nm）. Plasma samples were obtained from15d of embryogenesis （E15）to42d of posthatch （H42） according to sampling protocol. Compared to the control group,significantly higher plasma GH levels in embryos and chicks incubated under green lightwere observed from E19to H5（P <0.05）. Green light stimuli during incubation significantlyincreased plasma IGF-I levels of embryos from E17to E19, and of chicks from H3to H35compared with those incubated under dark condition （P <0.05）. No significant differenceswere found （P>0.05） in plasma T3, T4and testosterone in embryos or hatched chicksbetween the2groups, although green light group showed a trend in increasing plasma T3levels in hatched chicks from H7（P=0.09） to H21（P=0.06）. These data suggested thatsomatotropic axis hormone GH and IGF-I might be the most important contributor to chickgrowth promoted by green light stimuli during embryogenesis.Tiral3was carried out to assess whether the regulation of chicken embryonic orposthatch growth by green light stimuli during incubation was associated with the changes ofgrowth-related factors in pectoral muscle by measuring dynamical changes in mRNAexpression of GHR, IGF-I, IGF-IR and MSTN at different ages of embryogenesis andposthatching chicks. Compared to the birds in control group, green light stimuli duringincubation significantly up-regulated pectoral muscle GHR mRNA levels from E17to E19, and MSTN mRNA levels of embryos from E17to E19and of chicks from H5to H7（P <0.05）, respectively. No significant differences were observed in pectoral muscle IGF-I andIGF-IR mRNA levels of embryos between green light group and control group （P>0.05）.However, green light stimuli significantly up-regulated muscle IGF-I （from H3to H1） andIGF-IR （from H5to H7） mRNA levels of posthatch chicks （P <0.05）. These resultssuggested that green light stimuli during incubation promote posthatch muscle growth byup-regulating the expression of these growth-related factors and MSTN in late embryos andearly posthatch stage.Tiral4was conducted to further investigate the morphological and molecular basis ofthis phenomenon by measuring changes in BW, pectoral muscle weight, satellite cell mitoticactivity, and the developmental expression of MyoD and MyoG mRNA in pectoral muscle inembryos and early posthatch broilers. At7d of age （H7）, BW and pectoral muscle weight inthe green light group were significantly increased by14.33g and1.46g compared with birdsin the blue or dark groups （P <0.05）. Green light stimuli during embryogenesis significantlyincreased myofiber cross-sectional areas of pectoral muscle on H5to H7（P <0.05）. Index ofsatellite cell mitotic activity was also higher in the green light group on H1and H3（P <0.05）.Besides, in green light group, higher MyoD mRNA levels from E17to H3, and highermygenin mRNA levels from H1to H5were observed in pectoral muscle of embryos orbroiler （P <0.05）, respectively. These data suggested that green light stimuli duringembryogenesis promoted posthatch muscle growth by increasing satellite cell mitotic activity,enhancing myoblast proliferation and differentiation in late embryos and early posthatchstage.In summary, monochromatic green light stimuli during embryogenesis stimulated thesecretion of somatotropic axis hormone GH and IGF-I in late embryos and posthatch chicks,upregulated pectoral muscle growth-related factors （GHR and MSTN） and muscle regulatoryfactors （MyoD and MyoG） mRNA expression, increased satellite cell mitotic activity,enhanced myoblast proliferation and differentiation in late embryos and early posthatch stage,and improved subsequently pectoral muscle growth of posthatch broilers.更多还原