Estimating the voluntary intake and digestibility of buffel-grass and lucerne hays offered to Brahman-cross cattle using n-alkanes

Abstract

The n-alkane method was developed in temperate areas as a tool to estimate voluntary intake (VI) at pasture. The present study aimed to investigate the performance of n-alkanes as markers for estimating VI of steers (mean live weight 213 kg) offered a range of tropical grass hays and lucerne. Tropical and temperate forages have different n-alkane profiles and little is known about the issues which affect the accuracy of the method under tropical conditions. In two pen experiments (no. = 20 and no. = 24) n-alkanes were dosed using intraruminal controlled-release devices. Actual mean voluntary dry matter intakes for the diets ranged from 3·12 to 4·60 kg/day and actual mean dry-matter digestibility varied between 439 and 620 g/kg. n-Alkane profiles (C30 to C36) of the diets and the faeces for each animal were determined using gas chromatography. The recovery of each n-alkane was determined for each animal. Recoveries of n-alkanes were highly variable and generally varied between diets and between experiments. When adjacent n-alkanes were used to estimate VI (ratio method), agreement with actual VI was often poor. Despite this, where the recoveries of n-alkane pairs were similar, group mean VI were accurately estimated. From these data, it is concluded that estimation of VI in cattle offered tropical grass hays or lucerne hay, requires measured recoveries of both dosed and natural plant n-alkanes. The dosed and natural n-alkane pairs having the most similar recoveries should be used in the ratio method to estimate VI.

The potential use of long-chain alcohols and fatty acids as diet composition markers: factors influencing faecal recovery rates and diet composition estimates in sheep

“…Some studies have indicated that faecal alkane recoveries are unaffected by diet (Mayes et al, 1986;Brosh et al, 2003) or feeding level (Mayes et al, 1986;Dove et al, 1989;Dove and Olivá n, 1998;Elwert et al, 2004); whereas others reported that alkane recoveries were influenced by diet types (Dove et al, 1989;Hendricksen et al, 2002;Ferreira et al, 2005 and, feeding level (Dillon, 1993;Dove et al, 2002) or herbage species (Lin et al, 2007;Elwert et al, 2008). To date, little published data are available evaluating the effects of herbage species and live weight on faecal alcohol and acid recoveries.…”

The potential use of n-alkanes, long-chain alcohols and long-chain fatty acids as diet composition markers: indoor validation with sheep and herbage species from the rangeland of Inner Mongolia of China

“…Although a few direct comparisons of faecal marker recoveries from various herbage species exist, most of these studies came to the similar conclusion. In cattle, differences of faecal alkane recoveries were observed between herbage species (Ohajuruka and Palmquist, 1991;Hendricksen et al, 2002). In sheep, recent studies found an effect of herbage species on faecal recoveries of alkanes (Lin et al, 2007;Elwert et al, 2008), alcohols and acids (Lin et al, 2009a).…”

Estimation of faecal output, digestibility, and intake using a controlled release capsule of alkanes in early and late lactation dairy cows fed two levels of concentrate

“…Moreover, in the present experiment, concentrations of C 31 and C 33 in plant materials were low, which could also have increased the variation associated with DM intake estimates. Using the alkane C 35 to C 36 ratio, Hendricksen et al (2002) reported that estimation of DM intake was more variable when herbage alkane content was less than 20 mg kg -1 for an alfalfa-based diet. Estimation of intake using the double alkanes technique has been shown to be generally satisfactory in sheep (Dove et Mayes 1985Vulich et al 1991;Dove et al 2002), but results with cattle are more variable (Dillon and Stakelum 1989;Berry et al 2000;Hendricksen et al 2002;Charmley et al 2003), suggesting that additional research is required in the bovine.…”