Meissner H H, Paulsmeier D V
Department of Animal and Wildlife Sciences, University of Pretoria, Republic of South Africa.
J Anim Sci. 1995 Aug;73(8):2447-57. doi: 10.2527/1995.7382447x.
The purpose of the study was to identify plant compositional constituents that influence forage intake. Emphasis was put on the ratio in vitro digestibility of organic matter (IVDOM):NDF because preliminary work with cattle and a limited number of forages showed the ratio to account for more variation in intake than either IVDOM or NDF alone. The compositional constituents were tested in intake prediction models using local and published data (n = 302) on grass pastures, silages, hays, straws, legumes, grass-legume mixtures, and shrubs ingested by both browsing and grass-eating ruminants (goats, red deer, impala, blesbok, sheep, cattle, and blue wildebeest). In the local experiments, esophageally fistulated and fecal bag-harnessed animals were used to collect representative grazed forage samples from pastures and to determine OM excreted, respectively. Forage intake was calculated as OM excreted divided by (1-IVDOM). Intake of silages, hays, and straws was measured indoors in digestibility trials. Intakes among species were compared after scaling for size by BW raised to the power of .9. Major contributors to the variation in forage intake were ash, hemicellulose, IVDOM:NDF, ADL, and the interaction between DM content and, respectively, ash, N, and ADL. High tannin/phenol concentrations proved limiting to intake. The ratio of IVDOM:NDF accounted for 67% of the variation in forage intake if data for which the other constituents had an effect were omitted, and the equation, OMI, g.kg BW-.9.d-1 = 70-97e-.975(IVDOM:NDF), predicted intake across all forages and ruminant species with a Sy.x of 5.3 g.kg BW-.9.d-1 (CV = 15%). The ratio of IVDOM:NDF should be valuable as a relatively inexpensive and rapid method to screen forages and cultivars.
本研究的目的是确定影响采食量的植物组成成分。重点关注有机物体外消化率（IVDOM）与中性洗涤纤维（NDF）的比值，因为对牛和少量饲草的前期研究表明，该比值比单独的IVDOM或NDF能解释采食量更多的变异。使用本地和已发表的数据（n = 302）对组成成分进行采食量预测模型测试，这些数据涉及草牧场、青贮饲料、干草、秸秆、豆科植物、禾本科 - 豆科混合饲料以及被放牧和食草反刍动物（山羊、马鹿、黑斑羚、白纹牛羚、绵羊、牛和蓝角马）采食的灌木。在本地实验中，分别使用食管造瘘和佩戴粪袋的动物从牧场采集代表性的放牧饲草样本并测定排出的有机物。采食量计算为排出的有机物除以（1 - IVDOM）。青贮饲料、干草和秸秆的采食量在室内消化试验中进行测定。按体重的0.9次方进行大小校正后比较各物种间的采食量。采食量变异的主要影响因素是灰分、半纤维素、IVDOM:NDF、酸性洗涤木质素（ADL）以及干物质含量分别与灰分、氮和ADL之间的相互作用。高单宁/酚浓度被证明会限制采食量。如果省略其他成分有影响的数据，IVDOM:NDF的比值可解释采食量变异的67%，方程OMI，g.kg BW -0.9.d -1 = 70 - 97e -0.975(IVDOM:NDF)可预测所有饲草和反刍动物物种的采食量，其估计标准误Sy.x为5.3 g.kg BW -0.9.d -1（变异系数CV = 15%）。IVDOM:NDF的比值作为一种相对廉价且快速的饲草和品种筛选方法应具有重要价值。
