In vitro studies of the metabolism of [14C]-n-alkanes using ruminal fluid of sheep as substrate

Keli, A.; Mayes, R. W.; Vega, A. de

doi:10.1017/s1751731108003108

Cited by 12 publications

(16 citation statements)

References 21 publications

(29 reference statements)

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“…Although the site of degradation in the GI tract has not been identified definitively in ruminants, Mayes (1988) observed that the main site for n-alkane loss in sheep was the small intestine, whereas Ohajuruka and Palquist (1991) found that some n-alkane loss was occurring within the rumen in cattle. However, Keli et al (2008) found no synthesis or degradation of n-alkanes by rumen bacteria through in vitro manipulations using sheep ruminal fluid. Degradation of n-alkanes may be secondarily dependent upon a suite of other conditions in the rumen, including rumen passage rate, microbial efficiency, which depends on both energy and N supplies to the rumen, and the presence of plant microbial toxins such as terpenes.…”

Section: Discussionmentioning

confidence: 91%

n-Alkane and long-chain alcohol recovery in moose (Alces alces), a browsing herbivore

2018

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Habitat management for herbivores often depends on an understanding of the food habits of animals. Plant cuticular waxes containing nearly indigestible complex mixture of n-alkanes and long-chain alcohols (LCOHs) have recently shown promise for diet analyses, but the accuracy of the technique depends strongly on the efficiency of recovery of the markers in feces. Fecal recovery of n-alkanes and LCOHs from ten browse stems or leaves and two ensiled grass hays fed to moose (Alces alces (L., 1758)) during in vivo digestion trials was investigated. n-Alkanes and LCOHs were extracted using a single-step accelerated solvent extraction technique, and the recovery of these cuticular components was calculated from the feces of the animals. n-Alkane recoveries from feces averaged 0.82, but ranged from a low of 0.58 (haylage) to a high of 0.95 (browse stems). Long-chain alcohol recoveries averaged 0.92 across all forages, ranging from 0.80 (haylage) to a high of 1.13 (browse stems). n-Alkane and LCOH fecal recovery increased with increasing chain length, similar to findings in other studies. Although fecal recovery of nalkanes and LCOHs were variable, we conclude that they are inversely related to forage digestibility, are consistent within forage classes, and are therefore predictable markers for use in assessing herbivore diets.

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Section: Discussionmentioning

confidence: 91%

n-Alkane and long-chain alcohol recovery in moose (Alces alces), a browsing herbivore

2018

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“…Similar observations were reported for the biosynthesis of lignin [30] and starch [31] in plant tissue. Differential carbon allocation as observed in the plant tissue does not occur in the animal organism due to the absence of ruminal synthesis and degradation of n -alkanes [10], [11]. Microbial fermentation in the hindgut of ruminants is minor [32] and a hypothetical degradation of n -alkanes and preferential carbon isotope disappearance from the hindgut is therefore unlikely to affect passage kinetics estimations of n -alkanes from fecal samples.…”

Section: Discussionmentioning

confidence: 96%

“…Yet, no evidence for microbial incorporation is available with regard to the more common natural long-chain forage n -alkanes C 27 to C 35 used in our study. A recent in vitro study, in which 14 C labeled perennial ryegrass was incubated in buffered rumen fluid [11], suggested the complete absence of ruminal degradation and synthesis of long-chain n -alkanes by ruminal bacteria.…”

Section: Discussionmentioning

confidence: 99%

“…n -Alkanes are saturated aliphatic hydrocarbon chains naturally present in plant cuticular wax. They have a high fecal recovery in ruminants depending on the carbon chain length [8], [9], are neither degraded nor synthesized in the rumen [10], [11], and their analytical determination is sensitive and specific [7]; hence, they possess close-to-ideal tracer characteristics.…”

Section: Introductionmentioning

confidence: 99%

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Stable Isotope Labeled n-Alkanes to Assess Digesta Passage Kinetics through the Digestive Tract of Ruminants

et al. 2013

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We describe the use of carbon stable isotope (13C) labeled n-alkanes as a potential internal tracer to assess passage kinetics of ingested nutrients in ruminants. Plant cuticular n-alkanes originating from intrinsically 13C labeled ryegrass plants were pulse dosed intraruminally in four rumen-cannulated lactating dairy cows receiving four contrasting ryegrass silage treatments that differed in nitrogen fertilization level (45 or 90 kg nitrogen ha−1) and maturity (early or late). Passage kinetics through the gastrointestinal tract were derived from the δ13C (i.e. the ratio 13C:12C) in apparently undigested fecal material. Isotopic enrichment was observed in a wide range of long-chain n-alkanes (C27–C36) and passage kinetics were determined for the most abundant C29, C31 and C33 n-alkanes, for which a sufficiently high response signal was detected by combustion isotope ratio mass spectrometry. Basal diet treatment and carbon chain length of n-alkanes did not affect fractional passage rates from the rumen (K 1) among individual n-alkanes (3.71–3.95%/h). Peak concentration time and transit time showed a quantitatively small, significant (p≤0.002) increase with carbon chain length. K 1 estimates were comparable to those of the 13C labeled digestible dry matter fraction (3.38%/h; r = 0.61 to 0.71; p≤0.012). A literature review has shown that n-alkanes are not fermented by microorganisms in the rumen and affirms no preferential depletion of 13C versus 12C. Our results suggest that 13C labeled n-alkanes can be used as nutrient passage tracers and support the reliability of the δ13C signature of digestible feed nutrients as a tool to measure nutrient-specific passage kinetics.

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“…Controlled in vivo experiments may be required to document the relative fates of the two carbon isotopes in the gut. Gut microorganisms are unable to synthesise long-chain n-alkanes (Keli et al, 2008) indicating that there would be no bias in the estimation of diet composition due to endogenous n-alkane excretion into faeces. Due to the difficult nature of the measurement, the presence of differential recoveries (if any) of the same n-alkane originating from different plants has not yet been established.…”

Section: Pc1mentioning

confidence: 99%

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

Bezabih

Pellikaan

Tolera

et al. 2011

Animal

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Plant cuticular n-alkanes have been successfully used as markers to estimate diet composition and intake of grazing herbivores. However, additional markers may be required under grazing conditions in botanically diverse vegetation. This study was conducted to describe the n-alkane profiles and the carbon isotope enrichment of n-alkanes of common plant species from the Mid Rift Valley rangelands of Ethiopia, and evaluate their potential use as nutritional markers. A total of 23 plant species were collected and analysed for long-chain n-alkanes ranging from heptacosane to hexatriacontane (C 27 to C 36 ), as well as their carbon isotopic ratio ( 13 C/ 12 C). The analysis was conducted by gas chromatography/combustion isotope ratio mass spectrometry following saponification, extraction and purification. The isotopic composition of the n-alkanes is reported in the delta notation (d 13 C) relative to the Vienna Pee Dee Belemnite standard. The dominant n-alkanes in the species were C 31 (mean 6 s.d., 283 6 246 mg/ kg dry matter) and C 33 (149 6 98 mg/kg dry matter). The carbon isotopic enrichment of the n-alkanes ranged from 219.37% to 237.40%. Principal component analysis was used to examine interspecies differences based on n-alkane profiles and the carbon isotopic enrichments of individual n-alkanes. Large variability among the pasture species was observed. The first three principal components explained most of the interspecies variances. Comparison of the principal component scores using orthogonal procrustes rotation indicated that about 0.84 of the interspecies variances explained by the two types of data sets were independent of each other, suggesting that the use of a combination of the two markers can improve diet composition estimations. It was concluded that, while the n-alkane profile of the pasture species remains a useful marker for use in the study region, the d 13 C values of n-alkanes can provide additional information in discriminating diet components of grazing animals.

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In vitro studies of the metabolism of [14C]-n-alkanes using ruminal fluid of sheep as substrate

Cited by 12 publications

References 21 publications

n-Alkane and long-chain alcohol recovery in moose (Alces alces), a browsing herbivore

n-Alkane and long-chain alcohol recovery in moose (Alces alces), a browsing herbivore

Stable Isotope Labeled n-Alkanes to Assess Digesta Passage Kinetics through the Digestive Tract of Ruminants

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

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