Accuracy of the n-alkane technique for intake estimates in beef cattle using different sampling procedures and feeding levels

Abstract

The present study aimed to evaluate the reliability of the n-alkane technique for estimating herbage intake in beef cattle receiving two different feeding levels (low and high) and to test the effect of different faeces sampling procedures (total faeces samples or rectal grab samples at 8 h intervals) on the n-alkane faecal recoveries and hence on intake estimates. Two consecutive experiments were performed with 11 non-lactating beef cows of "Asturiana de los Valles" breed, fed with lucerne hay at two feeding levels: 1.0 or 1.7 kg DM/100 kg body weight (BW). Animals received a daily dose of paper pellets containing C 24 , C 32 and C 36 n-alkanes as external markers with the purpose of using different n-alkane pairs of adjacent chain length (C 23 /C 24 , C 25 /C 24 , C 31 /C 32 , C 33 /C 32 , C 35 /C 36 ) for intake calculations. A 5-day equilibrium period was sufficient for external marker concentrations and n-alkane pair ratios to reach steady state in faeces. There was no effect of different sampling times (every 8 h) on the faecal excretion of n-alkane pairs C 31 /C 32 and C 33 /C 32 . Grab samples obtained at the time of dosing (0830 h) gave the best estimate of n-alkane pair ratios in total faeces collection. There was a general trend of increasing n-alkane faecal recoveries with increased chain length, although n-alkanes C 30 , C 31 and C 33 showed lower faecal recoveries than expected. n-Alkane recoveries were in general lower at the low feeding level, where an increase in individual variability of natural n-alkane recoveries was observed. At both feeding levels, the n-alkane pairs C 23 /C 24 and C 35 /C 36 gave accurate estimates of the treatment average intake, although the natural n-alkane (C 23 or C 35 ) faecal recoveries showed high individual variability, which could be in part due to analytical bias caused by their extremely low concentration in the diet and faeces. However, the n-alkane pairs C 31 /C 32 and C 33 /C 32 gave the greatest deviations of intake estimates, due to the high discrepancy between the faecal recoveries of natural and dosed n-alkanes. These results demonstrate that in beef cattle, feeding level may have some influence on the relative faecal recoveries of the n-alkane pair used for intake calculations. This effect, together with the high individual variability of n-alkane recoveries, especially under low feeding level, may produce significant deviations of the individual intake estimates.

The importance of grasslands for animal production and other functions: a review on management and methodological progress in the tropics

“…Numerous studies have examined constraints and potential errors associated with use of these plant waxes, particularly n-alkanes, as markers (e.g. sampling of herbage, diurnal variation, faecal recovery of individual constituents, animal species) and there is consensus that in temperate pasture systems reliable results can be obtained (Dove and Mayes, 2005;Olivá n et al, 2007).…”

Application of long-chain alcohols as faecal markers to estimate diet composition of horses and cattle fed with herbaceous and woody species

“…In recent studies, grazing behaviour (diet selectivity and feed intake) of cattle and horses has been assessed by the use of long-chain saturated hydrocarbons (n-alkanes) as faecal markers (Ferreira et al, 2007 and2009a;Oliván et al, 2007a). As reviewed by Dove and Mayes (2006), this is a non-invasive approach offering several potential advantages over traditional methods.…”

Evaluation of n-alkanes and their carbon isotope enrichments (δ13C) as diet composition markers

“…In addition, they have high recovery rates in the faeces of herbivores (Ferreira et al, 2009), offering an opportunity to reconstitute the diet of the herbivore from the faecal patterns of these compounds Bugalho et al, 2004). Validation experiments revealed the potential of using n-alkanes to estimate intake, diet composition and nutrient digestibility of individual animals (Monks et al, 2005;Olivá n et al, 2007a).…”