Dove H, Charmley E
1CSIRO Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia.
Animal. 2008 Oct;2(10):1474-85. doi: 10.1017/S1751731108002735.
In a feeding trial with 24 sheep, we used the alkanes, long-chain alcohols (LCOH) or both of these plant wax markers, to estimate the diet composition of animals offered diets comprising alkane-labelled cottonseed meal (CSM) together with up to four forages. The diets used were: Diet 1 subterranean clover (Trifolium subterraneum); Diet 2 subterranean clover + phalaris (Phalaris aquatica); Diet 3 subterranean clover, phalaris + annual ryegrass (Lolium rigidum); and Diet 4 subterranean clover, phalaris, annual ryegrass + wheat straw (Triticum aestivum). Estimates of diet composition were made following correction of faecal alkane or LCOH concentrations for incomplete faecal recovery, using recovery estimates derived from individual animals, mean recoveries for a given dietary treatment or grand mean recoveries. Estimated dietary proportions of CSM and known intakes of CSM were used to estimate forage intake. The LCOH concentrations of the diet components were much higher than their alkane concentrations, especially for phalaris. Multivariate analyses showed that the discriminatory information provided by the LCOH was additional to that provided by the alkanes, and that a combination of (LCOH + alkanes) discriminated better between diet components than either class of marker alone. Faecal recoveries of LCOH increased with increasing carbon-chain length; there were no differences in recovery attributable to diet. The most accurate estimates of diet composition were obtained with the combination of (LCOH + alkanes). Estimates of diet composition based on LCOH alone were not as good as alkanes alone, due to the high correlation between the LCOH profiles of phalaris and ryegrass. Total grass content of the diet was very accurately estimated using LCOH. Diet composition estimates provided estimates of whole-diet digestibility, which did not differ from the measured values. Trends in the accuracy of forage intake estimates reflected those found with diet composition and almost two-thirds of estimates based on (LCOH + alkanes) had lower error than those found with alkanes alone. The results confirm that supplements labelled with plant wax components can be used to estimate forage intake, and also show that the LCOH are useful markers for estimating diet composition. Intakes were also computed using a combination of natural LCOH concentrations in the diet and the daily dose rate of even-chain alkanes administered by intra-ruminal device. Differences between intakes so estimated and the measured intakes were closely related to the difference in faecal recovery between the LCOH/alkane pair used to estimate intake, by an amount close to that expected on theoretical grounds. It is concluded that the use of plant wax LCOH, especially in combination with alkanes, will result in improved estimates of diet composition and intake in grazing animals.
在一项对24只绵羊的饲养试验中，我们使用链烷、长链醇（LCOH）或这两种植物蜡标记物来估计动物的日粮组成，这些动物的日粮包括用链烷标记的棉籽粕（CSM）以及多达四种草料。所使用的日粮如下：日粮1为地下三叶草（Trifolium subterraneum）；日粮2为地下三叶草 + 虉草（Phalaris aquatica）；日粮3为地下三叶草、虉草 + 一年生黑麦草（Lolium rigidum）；日粮4为地下三叶草、虉草、一年生黑麦草 + 小麦秸秆（Triticum aestivum）。在对粪便中链烷或LCOH浓度进行不完全粪便回收校正后，使用从个体动物得出的回收估计值、给定日粮处理的平均回收率或总平均回收率来进行日粮组成的估计。用CSM的估计日粮比例和已知的CSM摄入量来估计草料摄入量。日粮成分的LCOH浓度远高于其链烷浓度，尤其是虉草。多变量分析表明，LCOH提供的判别信息是链烷所提供信息之外的，并且（LCOH + 链烷）的组合在区分日粮成分方面比单独的任何一类标记物都更好。LCOH的粪便回收率随碳链长度增加而增加；回收率在不同日粮之间没有差异。用（LCOH + 链烷）的组合获得了最准确的日粮组成估计值。仅基于LCOH的日粮组成估计不如仅基于链烷的估计，这是由于虉草和黑麦草的LCOH谱之间存在高度相关性。使用LCOH非常准确地估计了日粮中的总草含量。日粮组成估计提供了全日粮消化率的估计值，这些估计值与测量值没有差异。草料摄入量估计准确性的趋势反映了日粮组成估计中发现的趋势，并且基于（LCOH + 链烷）的估计中近三分之二的误差低于仅基于链烷的估计。结果证实，用植物蜡成分标记的补充剂可用于估计草料摄入量，并且还表明LCOH是估计日粮组成的有用标记物。摄入量也使用日粮中天然LCOH浓度与通过瘤胃内装置施用的偶数链烷的日剂量率的组合来计算。如此估计的摄入量与测量摄入量之间的差异与用于估计摄入量的LCOH/链烷对之间的粪便回收率差异密切相关，其差异量接近理论预期值。得出的结论是，使用植物蜡LCOH，特别是与链烷结合使用，将提高对放牧动物日粮组成和摄入量的估计。
