【作者】 马涛；

【导师】 刁其玉；

【作者基本信息】 中国农业科学院 ， 动物营养与饲料科学， 2014， 博士

【摘要】 本研究以杜寒杂交肉用公绵羊为试验动物，利用微生物和食糜流量标记物技术，首先评价两种微生物氮（MN）实测标记物15N和嘌呤（PB）的效果，确立一种标准的实测方法；其次研究日粮处理（饲喂水平、精料比）对尿嘌呤衍生物（PD）排出量的影响，并建立PD预测MN的相关方程；最后开展评价点采样法预测PD排出量的研究。试验一、饲喂水平对肉羊尿嘌呤衍生物排出量的影响本试验旨在评价15N和PB测定瘤胃MN的效果，并研究饲喂水平对PD排出量的影响，初步建立PD预测MN的相关模型。选用12只6月龄杜寒杂交公羊，采用完全随机设计，按照自由采食（AL）、自由采食量的70%（70%AL）和自由采食量的50%（50%AL）三个干物质采食水平饲喂。结果表明，应用15N测定的MN变异程度低于应用嘌呤测定的结果（P<0.05）；尿囊素排出量在三组间差异显著（P<0.05），尿酸、黄嘌呤和次黄嘌呤排出量只在AL组和50%AL组间差异显著（P<0.05）；由15N估测的MN与PD排出量线性相关（P<0.05）：MN (g/d)=0.74×PD(mmol/d)+0.030, R2=0.91。试验二、日粮精粗比对肉羊尿嘌呤衍生物排出量及微生物蛋白质合成量的影响本试验旨在研究在广泛精粗比范围下PD排出量是否能够准确预测MN合成量，并提出十二指肠可代谢N的预测方程。选用12只10月龄杜寒杂交公羊，配制12种不同粗料精料比例（F:C）日粮，采用12×4不完全拉丁方试验，开展四期试验。结果表明，总PD、尿囊素排出量随F:C的降低显著升高（P<0.05），尿酸和黄嘌呤+次黄嘌呤排出量不受F:C的影响（P>0.05）；PNI和NCE均随日粮F:C的降低显著降低（P<0.05），且两者存在线性相关：NCE=3.67×PNI+0.574, R2=0.82；小肠可代谢N（Y, g/d）与可消化有机物（X1, g/d）或瘤胃表观可消化有机物（X2, g/d）采食量均存在二次相关： Y=0.0002X21–0.181X1+46.435, R2=0.81; Y=0.0002X22–0.081X2+16.961, R2=0.95；肉羊采食不同F:C日粮尿中PD排出量和应用15N实测得到的MN合成量存在线性相关，相关关系为：MN (g/d)=–0.52+1.49PD (mmol/d)(R2=0.86, n=45, P<0.05)。试验三、点采样法预测肉羊尿嘌呤衍生物排出量的有效性本试验旨在研究日粮碳水化化物与蛋白质组成对肉羊PD排出量的影响，并评价点采样估测PD排出量的准确性。选用4只10月龄杜寒杂交公羊，配制2种不同非结构性碳水化合物（NFC）水平和瘤胃非降解蛋白质（UDP）水平的饲粮，采用4×4拉丁方设计，于每期消化代谢试验的08:00–09:30、14:00–15:30和20:00–21:30三个时间段进行点采样。结果表明，在点采样过程中，PDC指数与全收尿PD排出量呈线性相关（P<0.05）：PD (mmol/d)=0.22×PDC+3.45, R2=0.88，表明点在本试验条件下采样能够准确估测全天PD排出量。更多还原

【Abstract】 This study used Dorper thin-tailed Han crossbred sheep were used to firstly compare the accuracyof two microbial nitrogen (MN) markers,15N and purine base (PB), and secondly to investigate theeffect of dietary treatments on urinary excretion of purine derivatives (PD), and finally to establish therelationship between PD and MN, and to evaluate the effectiveness of using spot urine samplingtechnique.Experiment1: Effect of feed intake on urinary excretion of purine derivatives and microbialprotein synthesis in mutton sheepThis study aimed to compare the MN measured by using two microbial markers,15N and PB, and toinvestigate the effect of dietary treatment on urinary PD excretion, and to establish the relationshipbetween MN and PD. Twelve6-month-old ram lambs were randomly assigned to three levels of drymatter intake: ad libitum (AL) intake, or70%(70%AL) or50%(50%AL) of the ad libitum intake. Theresults showed that: MN measured by15N had lower variability than that measured by PB (P<0.05).Urinary excretion of allantoin was affected by feed intake (P<0.05). Significant difference was found inurinary excretion of uric acid and xanthine+hypoxanthine between AL and50%AL groups (P<0.05).PD was linearly correlated with MN estimated from either15N or PB: MN (g/d)=0.74×PD (mmol/d)+0.030, R2=0.91.Experiment2: Effect of dietary forage to concentrate ratios on urinary excretion of purinederivatives and microbial protein synthesis in mutton sheepThis study aimed to establish the model for predicting MN using urinary PD, and to predict intestinalmetabolizable N. Twelve10-month-old ram lambs were randomly assigned to12levels of dietary F:Cin an incomplete Latin-square experimental design (12lambs4periods). The results showed that:Allantoin and total PD increased (P<0.05) with decreasing F:C. Uric acid and xanthine plushypoxanthine was unaffected by F:C (P>0.05). Both PNI and NCE decreased with decreasing F:C(P<0.05) and a linear relationship existed between PNI and NCE calculated with15N: NCE=3.67×PNI+0.574, R2=0.82. Metabolizable protein (Y, g/d) was quadriatically correlated with digestibileorganic matter (DOM; X1, g/d) or organic matter apparently digested in the rumen (OMADR; X2, g/d):Y=0.0002X21–0.181X1+46.435, R2=0.81; Y=0.0002X22–0.081X2+16.961, R2=0.95. A linearcorrelation was observed between PD excretion and MN: MN (g/d)=–0.52+1.49PD (mmol/d)(R2=0.86, n=45, P<0.05).Experiment3: Study on the effectiveness of use of spot urine samples to predict daily PDexcretionThis study aimed to investigate the effect of dietary treatment on PD excretion and to evaluate theeffectiveness of using spot urine technique to predict daily PD excretion. Four10-old-month ram lambswere randomly assigned to four dietary treatments including two levels of non-fibrous carbohydrate andtwo levels of undegraded dietary protein, according to a44Latin-square experimental design. During the digestibility trial, spot urines were collected between08:00–09:30,14:00–15:30, and20:00–21:30,respectively. In spot urine samples, a linear correlation existed between the PDC index from spot urinesamples and daily PD excretion (P<0.05): PD (mmol/d)=0.22×PDC+3.45, R2=0.88, whichindicated that spot sampling technique accurately predicted daily PD output.更多还原