Effects of ensiling time on corn silage neutral detergent fiber degradability and relationship between laboratory fiber analyses and in vivo digestibility
Effects of ensiling time on corn silage neutral detergent fiber degradability and relationship between laboratory fiber analyses and in vivo digestibility
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DOI：
10.3168/jds.2019-16917
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发表时间：
2020-03-01
影响因子：
3.5
通讯作者：
DiMarco, K.
中科院分区：
文献类型：
--
作者：
Hristov, A. N.;Harper, M. T.;DiMarco, K.
准确分析青贮饲料中性洗涤纤维（NDF）的降解率对奶牛日粮配方设计和泌乳性能预测具有重要意义。以5个玉米杂交种青贮0 d（未发酵）、30 d、60 d、120 d和150 d为试验材料，研究青贮时间对青贮饲料中性洗涤纤维降解率（NDFD）的影响，并探讨近红外反射光谱（NIR）NDF相关分析与原位NIWD变量之间的关系。此外，在16个试验的总混合日粮样品中，研究了日粮中288小时孵育的难消化NDF（iNDF 288）或240小时孵育的未降解NDF（uNDF 240）浓度与体内全道表观有机物和NDF消化率之间的关系。青贮时间对青贮NDF浓度没有影响，但随着青贮时间的延长，酸性洗涤纤维除以NDP的比例增加，半纤维素浓度呈二次曲线下降。随着青贮时间的延长，NDF结合蛋白的含量呈下降趋势，木质素的含量呈上升趋势。青贮纤维组成的这些变化导致青贮NDF的原位有效降解率随青贮时间的增加而线性下降。青贮时间对NDF的不消化率和结构性碳水化合物含量没有影响。原位NDFD变量与实验室近红外NDFD分析的相关性弱至中等。玉米青贮uNDF 240与木质素浓度或30-h NDFD（所有NIR分析）的关系非常好（R-2分别= 0.73和0.88）。在原位iNDF 288浓度（但不是uNDF 240）和在体内的饲料有机物和NDF的全消化道表观消化率之间的关系是良好的（R-2 = 0.72和0.80，分别）。总之，在原位降解青贮NDF线性下降0至150 d青贮时间，主要是由于半纤维素和NDF结合蛋白的浓度下降。现场NDF降解性测量和常见的实验室近红外NDF相关分析通常相关性较差。我们发现，在体内NDF消化率和饲料中的iNDF 288浓度原位测定之间有很好的关系，但与uNDF 240的关系较差。
Accurate analysis of degradability of silage neutral detergent fiber (NDF) is important for diet formulation and to predict lactational performance of dairy cows. In this study, 5 corn silage hybrids ensiled for 0 (unfermented), 30, 60, 120, and 150 d were used to determine the effects of ensiling time on silage neutral detergent fiber degradability (NDFD) and to assess the relationships between near-infrared reflectance spectroscopy (NIR) NDF-related analyses and in situ NIWD variables. In addition, the relationships between dietary concentration of indigestible NDF, 288-h incubation (iNDF288), or undegraded NDF, 240-h incubation (uNDF240), and in vivo total-tract apparent organic matter and NDF digestibility were studied in total mixed ration samples from 16 experiments with lactating dairy cows. Ensiling time had no effect on silage NDF concentration; however, the ratio of acid detergent fiber divided by NDP increased, and estimated hemicellulose concentration decreased quadratically with ensiling time. Also, concentration of NDF-bound protein decreased, and that of lignin increased linearly with ensiling time. These changes in silage fiber composition resulted in a linear decrease in in situ effective degradability of silage NDF with increasing ensiling time. The indigestible fraction of NDF and concentration of structural carbohydrates were not affected by ensiling time. Correlations of in situ NDFD variables with laboratory NIR NDFD analyses were weak to moderate. The relationship of corn silage uNDF240 with lignin concentration or 30-h NDFD (all NIR analyses) was remarkably good (R-2 = 0.73 and 0.88, respectively). The relationship between in situ iNDF288 concentration (but not uNDF240) and in vivo total-tract apparent digestibility of dietary organic matter and NDF was good (R-2 = 0.72 and 0.80, respectively). In conclusion, in situ degradability of silage NDF linearly decreased from 0 to 150 d ensiling time, primarily caused by a decrease in concentrations of hemicellulose and NDF-bound protein. In situ NDF degradability measurements and common laboratory NIR NDF-related analyses were generally poorly correlated. We found a good relationship between in vivo NDF digestibility and dietary concentration of iNDF288 determined in situ, but the relationship with uNDF240 was poor.