Using the n-alkanes of plant cuticular wax to estimate the species composition of herbage mixtures

Abstract

This study examined whether or not between-species differences in the concentrations of saturated hydrocarbons (n-alkanes) in the cuticular wax of pasture species could be exploited to estimate the species composition of herbage mixtures. Six sets of mixtures were prepared, containing either two, three or four species. The levels of cuticular wax alkanes were estimated in samples of the pure species and the mixtures, and used in simultaneous equations to compute species composition. The levels of Lolium perenne and Trifolium subterraneum in mixtures of these two species were accurately estimated from alkane analyses, as were the levels of these two species and Holcus lanatus when all three were mixed. In mixtures of T. subterraneum, L. rigidum and Phalaris aquatica, the first two species were well estimated, but phalaris was under-estimated, perhaps because of its relatively low alkane levels. In mixtures of these three species and Medicago sativa, the amounts of the grass species were estimated accurately, but the two legume species were not well distinguished from each other. However, total legume content was estimated very accurately. The species composition of mixtures of T. subterraneum and the above three grasses was also accurately estimated. It is concluded that the use of cuticular wax alkanes should allow a greater differentiation of herbage mixtures into their component species than was possible in previous studies using other markers. Results are also presented to indicate that ratios of alkane concentrations, especially the ratio of C29:C33 alkanes, can also be used to quantify, or at least rank, the clover content of herbage mixtures.

Using the alkanes and long-chain alcohols of plant cuticular wax to estimate diet composition and the intakes of mixed forages in sheep consuming a known amount of alkane-labelled supplement

“…Plant wax profiles of the forages and CSM We have reported elsewhere on the alkane profiles of the diet components in the present study (Charmley and Dove, 2007) and drawn attention to the fact that the low alkane concentrations in phalaris, whilst typical of the species (Dove, 1992), made it difficult to estimate diet composition and forage intake in diets containing large proportions of this species. By contrast, LCOH concentrations in the diet components were much higher than their alkane concentrations.…”

“…Further investigation suggested that this had occurred as a result of the strong correlation between the LCOH profiles of the phalaris and ryegrass (r 5 0.989). Dove (1992) presented data indicating that, whilst it was difficult to distinguish subterranean clover and lucerne in herbage mixtures because their alkane profiles were highly correlated, total legume content of the mixtures was well estimated. By analogy in the present study, we recalculated the diet composition of sheep consuming Diet 4 based on the LCOH profiles of CSM, subterranean clover and a 'total grass' fraction.…”

Prediction of Diet Composition and Intake of Sheep Grazing Soybean and Maize Residues

“…The diet composition was estimated according to Dove and Mayes (1991) and Dove (1992) using alkane profile (fingerprint) of faeces for each sheep and the profiles of the individual component of t h e diet. Diet composition was calculated using software "Eatwhat" established by Dove and Moore (1995) based on least-squares optimization procedure.…”

Uso de n-alcanos na estimativa da composição botânica da dieta em ovinos alimentados com diferentes proporções de Brachiaria decumbens Stapf e Arachis pintoi Koprov e Gregory

“…A composição de espécies forrageiras disponíveis para o pastejo é uma característica importante nos estudos nutricionais, especialmente em pastagens consorciadas que possam proporcionar melhor desempenho animal com a presença de leguminosas ou em pastagens com maior proporção de leguminosas (Dove, 1992).…”

“…Entre as metodologias existentes, Dove & Mayes (1999) destacaram o uso dos indicadores naturais presentes nas plantas, os n-alcanos, pois não prejudicam a saúde dos animais ou do homem e possibilitam estimativas acuradas da ingestão de MS e da composição botânica das dietas consumidas pelos animais.…”