Dove H, Mayes R W
Division of Plant Industry, CSIRO, Canberra, Australia.
J Nutr. 1996 Jan;126(1):13-26. doi: 10.1093/jn/126.1.13.
The nutrient status of the herbivore depends on the nutritive value of the plants available, the botanical composition of the consumed diet and the intake of the animal. It has always been difficult to quantify these last two. At present, intake is usually calculated from separate estimates of fecal output and diet digestibility. In this review we discuss the errors inherent in this approach, especially those associated with the determination and application of digestibility in vitro. We then critically evaluate a new approach to the estimation of intake, based on the use of plant cuticular wax alkanes as markers. Plant alkanes are predominantly odd-chain and substantially indigestible. They can be used, in combination with orally dosed even-chain alkanes, to obtain an intake estimate which is essentially independent of marker recovery in feces and which is more truly "individual" because it accommodates the level of digestibility occurring in individual animals. We present published data which indicate that the method is accurate and can be extended to measure diet composition as well. Previous approaches to estimating diet composition have been based on the laborious microscopic examination of esophageal extrusa, stomach contents or feces. However, most plant species have a characteristic pattern of alkane concentrations in their cuticular wax. This permits the estimation of diet composition from the pattern of alkanes in the feces and in the plants available. We present data to show that this approach can provide accurate estimates of diet composition in terms of either plant species or plant parts. A major advantage of the approach is that, if the animals are also dosed with even-chain alkanes, estimates of total intake and diet composition can be obtained simultaneously. The method is equally applicable to domestic and wild herbivores and to animals receiving supplementary feeds. In future work, the method will be extended to the simultaneous estimation of plant species and plant parts in the diet, and to the use of other wax components as markers.
食草动物的营养状况取决于可获取植物的营养价值、所食用日粮的植物组成以及动物的摄入量。一直以来，对后两者进行量化都很困难。目前，摄入量通常是根据粪便排出量和日粮消化率的单独估算值来计算的。在本综述中，我们讨论了这种方法固有的误差，尤其是那些与体外消化率的测定和应用相关的误差。然后，我们批判性地评估了一种基于使用植物表皮蜡烷作为标记物来估算摄入量的新方法。植物烷烃主要是奇数链的，且基本不可消化。它们可以与口服的偶数链烷烃结合使用，以获得一个摄入量估算值，该估算值基本上与粪便中标记物的回收率无关，并且更具“个体性”，因为它考虑了个体动物的消化率水平。我们展示了已发表的数据，这些数据表明该方法是准确的，并且还可以扩展用于测量日粮组成。以前估算日粮组成的方法是基于对食管挤出物、胃内容物或粪便进行费力的显微镜检查。然而，大多数植物物种在其表皮蜡中的烷烃浓度具有特征模式。这使得可以根据粪便中和可获取植物中的烷烃模式来估算日粮组成。我们展示的数据表明，这种方法可以在植物物种或植物部分方面提供准确的日粮组成估算值。该方法的一个主要优点是，如果给动物也投喂偶数链烷烃，就可以同时获得总摄入量和日粮组成的估算值。该方法同样适用于家养和野生食草动物以及接受补充饲料的动物。在未来的工作中，该方法将扩展到同时估算日粮中的植物物种和植物部分，并扩展到使用其他蜡成分作为标记物。
