Mayes R W, Dove H
Macaulay Land Use Research Institute, Craigiebuckler, Aberdeen AB15 8QH, Scotland, UK.
Nutr Res Rev. 2000 Jun;13(1):107-38. doi: 10.1079/095442200108729025.
The nutrient intakes of mammalian herbivores depend on the amount and the nutrient content of the plant species and plant parts which they eat. We review the merits of oesophageal-fistulated (OF) animals, microhistological procedures, stable C-isotope discrimination and plant cuticular-wax markers as methods for estimating diet composition and intake in both ruminant and non-ruminant herbivores. We also briefly discuss methods based on grazing behaviour measurements or on H2O or Na turnover, and methods for estimating supplement or soil intake. Estimates of intake in ruminants are often based on separate measurements of faecal output and herbage digestibility. We review this approach and emphasize that, under some circumstances, the applicability of in vitro digestibility estimates based on OF extrusa is questionable. We discuss how plant-wax marker patterns can be used to check whether OF and test animals are consuming similar diets, but also emphasize that a major advantage of the use of plant-wax markers is that this approach may obviate altogether the need for OF animals. Estimates of total herbage intake can be partitioned into the intakes coming from different plant species and/or parts, provided diet composition can be measured. Diet composition estimates based on C-isotope discrimination have the major disadvantage that they cannot be taken to species level. By contrast, microhistological methods can identify many plant species in extrusa, digesta or faeces, but often a large proportion of plant fragments remains unidentifiable. Plant-wax hydrocarbons show great promise as markers for estimating diet composition and intake. However, we suggest that to be applicable in complex plant communities there is a need with this method either to recruit a wider range of wax markers (e.g. alcohols, sterols, fatty acids) or to use it in combination with other methods. We suggest that, in turn, this generates an urgent need for research on statistical aspects of the combined use of markers or methods, in relation to the error structures of the data or methods being combined and the standard errors of the resultant estimates of diet composition and intake. We conclude by discussing the extension of intake and/or diet composition measurements to the measurement of nutrient transactions within the gut, particularly in relation to the supply of absorbable nutrients.
哺乳动物食草动物的营养摄入量取决于它们所食用的植物种类和植物部位的数量及营养成分。我们综述了食管造瘘（OF）动物、微观组织学方法、稳定碳同位素判别以及植物表皮蜡标记物作为估算反刍动物和非反刍动物食草动物饮食组成和摄入量方法的优缺点。我们还简要讨论了基于放牧行为测量或水或钠周转率的方法，以及估算补充饲料或土壤摄入量的方法。反刍动物摄入量的估算通常基于对粪便产量和牧草消化率的单独测量。我们综述了这种方法，并强调在某些情况下，基于OF挤出物的体外消化率估算的适用性值得怀疑。我们讨论了如何利用植物蜡标记物模式来检查OF动物和试验动物是否食用相似的食物，但也强调使用植物蜡标记物的一个主要优点是这种方法可能完全无需使用OF动物。如果能够测量饮食组成，总牧草摄入量的估算可以细分为来自不同植物种类和/或部位的摄入量。基于碳同位素判别的饮食组成估算的主要缺点是无法精确到物种水平。相比之下，微观组织学方法可以识别挤出物、消化物或粪便中的许多植物种类，但通常很大一部分植物碎片仍无法识别。植物蜡烃作为估算饮食组成和摄入量的标记物显示出巨大潜力。然而，我们认为，要适用于复杂的植物群落，这种方法需要引入更广泛的蜡标记物（如醇类、甾醇、脂肪酸），或者与其他方法结合使用。我们进而认为，这迫切需要开展关于标记物或方法联合使用的统计学研究，涉及所结合数据或方法的误差结构以及饮食组成和摄入量最终估算值的标准误差。我们最后讨论了将摄入量和/或饮食组成测量扩展到肠道内营养物质交换测量的问题，特别是与可吸收营养物质供应相关的问题。
