【作者】 温超；

【导师】 王恬； 周岩民；

【作者基本信息】 南京农业大学 ， 动物营养与饲料科学， 2013， 博士

【摘要】 关于不同初生重肉鸡生产性能的差异已有大量报道,大部分试验结果表明高初生重肉鸡的生产性能优于低初生重肉鸡,但有关其生长发育规律和营养调控方面的研究鲜见报道。为此,本论文旨在研究不同初生重肉鸡的生长发育规律,并选择蛋氨酸为试验材料,探讨日粮蛋氨酸水平对不同初生重肉鸡生长发育的调控作用及相关机理,为不同初生重肉鸡营养调控研究提供参考依据。本文分为以下五个部分：试验一旨在调查不同周龄肉种鸡的雏鸡初生重分布情况。选择产蛋高峰(32周龄)、产蛋后期(53周龄)和强制换羽8周后(68周龄)的AA肉种鸡所产的健康雏鸡各500只,逐个称重用于统计初生重分布情况。结果表明,各周龄肉种鸡所产雏鸡初生重呈正态分布,平均值分别为42.87g、48.24g和47.33g,变异系数均在7%-8%之间,分别有74.4%、17.0%和28.8%的雏鸡初生重小于45g,有24.4%、52.0%和49.0%介于45g和50g之间,有1.2%、31.0%和22.2%大于50g。试验二旨在测定不同初生重和性别肉鸡生产性能、器官发育、血液生理生化指标、养分利用率、胰腺消化酶活性随日龄的变化规律。将初生重为42.3±0.3g和51.2±0.1g的AA肉雏鸡各192只(公母各半)按2×2因子分为4组,每组8个重复,饲喂相同日粮(粉料),试验为期42d。结果表明,高初生重肉鸡21d、42d的BW和前、后及全期ADG显著大于低初生重肉鸡(P<0.05),公鸡42d的BW及后期和全期ADG、ADFI大于母鸡(P<0.05),两者互作均无显著影响。高初生重肉鸡卵黄囊重量和不含卵黄囊体重大于低初生重肉鸡(P<0.05),21和42d胸肌相对重量显著大于后者(P<0.05),在28d和35d也表现出相同趋势(P=0.058),对其他器官相对重量基本无影响。初生重对血清生理生化指标、养分表观利用率和胰腺消化酶活性无影响。试验三旨在研究日粮蛋氨酸水平对不同初生重肉鸡生长发育的影响。选用初生重为41.73±0.04g和48.30±0.04g的1d健康AA肉鸡各96只,按2×2因子分为4组,每组6个重复,每个重复8只(公母各半),对照日粮蛋氨酸水平按NRC(1994)配制,高蛋氨酸日粮在对照日粮中额外添加0.1%蛋氨酸。结果表明,饲喂对照日粮时高初生重肉鸡21d、42d的BW和前期、全期ADG显著大于低初生重肉鸡(P<0.05),血清生化指标和器官相对重量无显著差异,高初生重肉鸡42d胸肌DNA含量与低初生重肉鸡相比显著下降(P<0.05),而RNA/DNA和IGF-I含量显著提高(P<0.05)。提高蛋氨酸水平使低初生重肉鸡42d的BW及后期和全期ADG显著提高(P<0.05),前后期及全期F/G显著下降(P<0.05),使高初生重肉鸡42d血清UA和TG含量显著提高(P<0.05),使低初生重肉鸡的胸肌相对重量显著提高(P<0.05),21d和42d胸肌DNA含量显著减少(P<0.05),而42d的胸肌RNA/DNA和蛋白/DNA及IGF-Ⅰ含量显著提高(P<0.05)。试验四旨在研究日粮蛋氨酸水平对不同初生重肉鸡胸肌发育调控基因表达及MSTN基因甲基化的影响,试验设计同试验三。结果表明,饲喂对照日粮时不同初生重肉鸡胸肌中各基因的表达量和MSTN甲基化率无显著差异,提高蛋氨酸水平使低初生重肉鸡胸肌Myf5和MEF2B的mRNA表达量显著提高(P<0.05),MSTN的mRNA表达量显著下降(P<0.05),其甲基化率显著提高(P<0.05)。试验五旨在研究日粮蛋氨酸水平对不同初生重肉鸡胸肌IGF-Ⅰ信号通路的影响,试验设计同试验三。结果表明,饲喂对照日粮时高初生重肉鸡胸肌IGF-Ⅰ的mRNA表达量显著大于低初生重肉鸡(P<0.05),提高蛋氨酸水平使低初生重肉鸡胸肌IGF-Ⅰ和TOR的mRNA表达量及p-TOR/TOR显著提高(P<0.05),使4EBP1、FOXO4和atrogin-1的mRNA表达量及p-FOXO4/FOXO4显著下降(P<0.05)。综上所述,得出以下结论：(1)肉鸡初生重随种鸡周龄增加而逐渐提高,在种鸡换羽后有所下降；肉种鸡处于产蛋高峰期时大部分雏鸡初生重小于45g,处于产蛋后期时大部分在45g以上。(2)高初生重肉鸡的日增重大于低初生重肉鸡,主要是胸肌发育速度不同所致；初生重与性别之间不存在互作效应。(3)在日粮中添加0.1%蛋氨酸不影响高初生重肉鸡生产性能,但显著改善低初生重肉鸡生产性能和胸肌发育,这可能与其胸肌IGF-I含量提高有关。(4)提高日粮蛋氨酸水平可能是通过提高胸肌Myf5和MEF2B的基因表达量及MSTN基因甲基化水平,降低MSTN的基因表达量,从而促进胸肌发育。(5)高蛋氨酸日粮对低初生重肉鸡胸肌发育的促进作用可能是通过提高IGF-I基因表达量,进而调控TOR/4EBP1和FOXO4/atrogin-1信号通路实现的。更多还原

【Abstract】 Extensive studies have demonstrated that broiler chicks with high hatching weight (HW) have better growth performance than those with lower HW, but up to date little attention has been paid to their physiological differences and nutritional regulations. Therefore, the objective of this study was to investigate the growth and development of broilers with different HW, and to evaluate the regulatory effects of dietary methionine (Met) and underlying mechanism. The study was composed of5trials as below:Trial1was conducted to investigate the HW distribution of broiler chicks from breeders of different age groups. Three batches (500birds each) of one-day-old Arbor Acres (AA) broiler chicks were selected from peak (32wk), late (53wk) and molted (68wk) breeders. They were weighed individually to analyze the HW distribution. The HW of chicks were normally distributed, and the mean value was42.87,48.24and47.33g, respectively, and CV was7%-8%. Among the three batches of chicks,74.4%,17.0%and28.8%of chicks were below45g,24.4%,52.0%and49.0%were between45and50g, and1.2%,31.0%and22.2%were above50g.Trial2was conducted to determine the growth performance, organ development, serum physiological and biochemical parameters, nutrient utilization, pancreatic enzyme activities of broilers with different HW and genders. A total of384day-old AA broiler chicks (half male and half female) with different HW (heavy:51.2±0.1g, and light:42.3±0.3g) were allocated to a randomized block design with a2×2factorial arrangement with4treatments. Each treatment had8replicates and12chicks per replicate. Chicks were fed the same starter and finisher mash diets for42days. The BW at21and42d and ADG were greater in heavy chicks than in light chicks during whole growth period (P<0.05). Male birds had a greater BW than female birds at42d (P<0.05). The ADG and ADFI of male birds were greater than those of female birds during finisher and overall phase (P<0.05). The interaction between HW and gender was not significant for growth performance of broilers. Heavy chicks had greater yolk sac weight and yolk-free BW than light chicks (P<0.05). The relative weight of breast muscle at21and42d was greater in heavy than in light birds (P<0.05), and the same trend was observed at28and35d. However, the relative weights of other organs did not differ. Gender and HW did not affect serum parameters tested, nutrient utilization or pancreatic enzyme activities.Trial3was conducted to evaluate the effect of dietary Met levels on growth and development of broilers with different HW. A total of192one-day-old AA broiler chicks with different HW (heavy:48.30±0.04g, and light:41.73±0.04g) were allocated to a2×2factorial arrangement with6replicates of8chicks (half male and half female). Met in the control diets was formulated to meet NRC recommendations, and high Met diets were manufactured by supplementing0.1%Met to the control diets. Light chicks had lower BW and ADG than heavy chicks when both were fed the control diets (P<0.05), whereas serum biochemical parameters or relative organ weights did not differ. Compared with light chicks, heavy chicks had lower DNA content in breast muscle at42d and higher RNA/DNA and IGF-I content (P<0.05). High Met diets improved42-d BW and ADG during finisher and whole phase as well as F/G in light chicks (P<0.05). Serum uric acid and triglyceride concentrations were increased by Met in heavy chicks at42d (P<0.05). Increasing Met levels increased42-d breast muscle yield and decreased its DNA concentration in light chicks at21and42d (P<0.05), whereas RNA/DNA, protein/DNA and IGF-I concentrations were increased at42d (P<0.05).Trial4was conducted to determine the effect of dietary Met levels on expression of genes related to muscle development and MSTN methylation in broilers with different HW. Experiment design was the same as that of Trial3. No difference was observed in the parameters tested when the birds were fed the control diets. High Met diets upregulated the mRNA levels of Myf5and MEF2B and the MSTN methylation and downregulated that of MSTN in breast muscle of light chicks (P<0.05).Trial5was conducted to explore the effect of dietary Met levels on the IGF-I signaling pathway in broilers with different HW. Experiment design was the same as that of Trial3. Heavy chicks had higher IGF-I mRNA expression in breast muscle than light chicks when both were fed the control diets (P<0.05). High Met diets increased the mRNA expressions of IGF-I, TOR and p-TOR/TOR in breast muscle of light chicks (P<0.05). Inversely, the mRNA expressions of4EBP1, FOXO4, atrogin-1and p-FOXO4/FOXO4were decreased in light chicks (P<0.05).It can be concluded as follows:(1) The HW of chicks increased as breeders ages before molting. Most of chicks from peak breeders had HW less than45g, and most of chicks from late breeders had HW greater than45g.(2) Heavy chicks had a greater ADG than light chicks, which may be due to different growth rate of breast muscles, and there was no interaction between HW and gender.(3) Adding0.1%Met to the control diets did not affect the performance of heavy chicks, but improved that of light chicks and breast muscle development, which may be related to increased IGF-I concentration in breast muscle.(4) Increasing Met levels may promote breast muscle development of light chicks by upregulating mRNA expression of Myf5and MEF2B genes and downregulating that of MSTN gene, which be associated with increased MSTN DNA methylation.(5) Increasing Met levels may improve breast muscle growth of light chicks by upregulating IGF-I mRNA expression, which further activated TOR/4EBP1and FOXO4/atrogin-1pathway.更多还原