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

Influence of Cuticular Waxes from Triticale on Rumen Fermentation: A Metabolomic and Microbiome Profiling Study

Cuticular wax, a critical defense layer for plants, remains a relatively unexplored factor in rumen fermentation. We investigated the impact of cuticular wax on rumen fermentation using triticale as a model. In total, six wax classes were identified, including fatty acids, aldehydes, alkane, primary alcohol, alkyresorcinol, and β-diketone, with low-bloom lines predominated by 46.05% of primary alcohols and high-bloom lines by 35.64% of β-diketone. Low-wax addition (2.5 g/kg DM) increased the gas production by 19.25% (P < 0.05) and total volatile fatty acids by 6.34% (P > 0.05), and enriched key carbohydrate-fermenting rumen microbes like Saccharofermentans, Ruminococcus, and Prevotellaceae, when compared to non-wax groups. Metabolites linked to nucleotide metabolism, purine metabolism, and protein/fat digestion in the rumen showed a positive correlation with low-wax, benefiting rumen microbes. This study highlights the intricate interplay among cuticular wax, rumen microbiota, fermentation, and metabolomics in forage digestion, providing insights into livestock nutrition and forage utilization.

Application of Fourier transform infrared spectroscopy (FTIR) techniques in the mid-IR (MIR) and near-IR (NIR) spectroscopy to determine n-alkane and long-chain alcohol contents in plant species and faecal samples

n-Alkanes and long-chain alcohols (LCOH) have been used as faecal markers to assess the feeding behaviour of both wild and domestic herbivore species. However, their chemical analysis is time-consuming and expensive, making it necessary to develop more expeditious methodologies to evaluate concentrations of these markers. This work aimed to evaluate the use of Fourier Transform Infrared Spectroscopy (FTIR) technology in the near infrared (NIR) and mid infrared (MIR) intervals, for the determination of n-alkane and LCOH concentrations of different plant species and faecal samples of domestic herbivores. Spectra of 33 feed samples, namely L. perenne, T. repens, U. gallii, short heathers (mixture of Erica spp. and Calluna vulgaris), improved pasture grasses (mixture of L. perenne and A. capillaris), heath grasses (mixture of P. longifolium and A. curtissii), improved pasture species (mixture of L. perenne, T. repens and A. capillaris) and herbaceous species (mixture of all herbaceous species found in the plot)) and 181 faecal samples (cattle and horses) were recorded. In order to develop calibrations for the prediction of n-alkanes and LCOH concentrations, partial least squares (PLS) regression was used. Regarding the models developed for plant species, the best results were observed for the calibrations using NIR. The best external validation coefficients of determination (R²v) obtained were 0.90 and 0.79 for LCOH and n-alkanes, respectively. For faecal samples, in the NIR interval, results indicate similar external validation predictions (R²v) for both animal species (0.64). On the contrary, in the MIR interval, differences between cattle (0.70) and horses (0.57) faecal samples in R²v were observed. Regarding the models created for both animal species faeces, LCOH (C₂₆-OH and C₃₀-OH concentrations ranging from 713.3 to 4451.9 mg/kg DM, respectively; R²v values ranging from 0.72 to 0.95) and n-alkanes (C31 and C33 concentrations ranging from 112.8 to 643.2 mg/kg DM, respectively; R²v values ranging from 0.19 to 0.90) present in higher concentrations tended to be those with better estimates. Results obtained suggest that the selection of the technique to be used may depend on the type of matrix, being the homogeneity of the matrices one of the most important factors for its success. In order to improve the accuracy and robustness of the models created for the estimation of the concentrations of these markers using these methodologies, the database (greater variability) used for the calibrations of these models must be increased.

Assessment of diet composition of free-ranging addax antelopes (Addaxnasomaculatus) by the combination of microhistological procedures andn-alkanes and long-chain alcohols as fecal markers

Understanding herbivore foraging behaviour is crucial for adequate wildlife management decisions. This study assessed the diet composition of free-ranging addax antelope (Addax nasomaculatus (de Blainville, 1816)). Samples collected during the spring season were analyzed using microhistological procedures along with n-alkanes and long-chain alcohols as fecal markers. Twelve animals were monitored and fresh fecal samples were collected daily during a 7-day period. Diet composition estimates obtained by both methods were similar and indicate that Stipagrostis pungens (Desf.) De Winter was the main diet component followed by Fagonia glutinosa Delile, Helianthemum kahiricum Delile, and Hammada schmittiana (Pomel.) Botsch. Data showed that addax have mixed diets composed of perennial woody and herbaceous plant species depending on their availability. The four species most selected by the animals were also the most abundant species in terms of plant cover. In contrast, species that accounted for less than 5% of the plant cover were not present in the fecal samples. Results of this study represent a single grazing season, and for that reason, further studies are required to fully understand how the grazing behaviour of addax varies with seasonal changes in vegetation cover.

Herbivore-Diet Analysis Based on Illumina MiSeq Sequencing: The Potential Use of an ITS2-Barcoding Approach to Establish Qualitative and Quantitative Predictions of Diet Composition of Mongolian Sheep

DNA-barcoding approaches to estimate the diet compositions of grazing animals have received significant attention, and particularly when combined with next-generation sequencing, these techniques have substantially improved in recent years. In this study, the identity and species composition of plant material ingested by Mongolian sheep were estimated through the use of 350 bp ITS2 gene sequences of the vegetation found in fecal samples. Four diets were formulated using varying amounts of eight plant species that are common in the grasslands of northern China. Sixteen Mongolian sheep were taken from pastures and randomly assigned to four groups, and each group received one of four diets. Each sheep was randomly assigned to one of 16 confinement pens and fed its respective diet for 12 consecutive days. Fecal samples were removed from each pen from days 7-12, preserved, and composited for each pen. All herbage species included in the daily diets were detected in each fecal sample, with the exception of Phragmites australis. Moreover, 12 additional different plant species were retrieved from feces of the experimental sheep. The obtained data provided preliminary support for the use of the ITS2 barcode to determine which plants were consumed. Moreover, the proportions of the herbage DNA sequences recovered from sheep feces and those of the herbage masses in the daily diets did not completely match. These results indicate that the non-Gramineae DNA sequences amplified with ITS2 primers (including those of Chenopodium album, Artemisia scoparia, Artemisia tanacetifolia, and Medicago sativa) far exceeded those of the Gramineae species (including Leymus chinensis and Puccinellia distans), which constitute the largest share of the experimental diets. A significant positive correlation (Spearman's ρ = 0.376, P = 0.003) between the actual herbage mass proportions in the experimental diets and the herbage-DNA-sequence proportions provided sufficiently favorable support for the further investigation of DNA barcoding for the quantification of plants in feces. A significant regression coefficient was found between the relative DNA-sequence proportions of L. chinensis ( R² = 0.82, P < 0.0001), P. distans ( R² = 0.64, P = 0.0017), and C. album ( R² = 0.98, P < 0.0001) and their respective herbage mass proportions. The quantitative relationship can be expressed by the linear-regression equations y = 0.90 x - 0.22, y = 0.98 x - 0.03, and y = 5.00 x - 0.25, respectively. Thus, these results demonstrate that dietary-DNA-barcoding methods exhibited potential in providing valuable quantitative information regarding food-item components. However, it should be noted that this explorative data needs to be further improved by using additional genes and by creating a sophisticated reference database, thus enhancing both quality and accuracy of the obtained results.

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

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 10 browse stems or leaves and two ensiled grass hays fed to moose (Alces alces (Linnaeus, 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, ranging from a low of 0.58 (haylage) to a high of 0.95 (browse stems). LCOH 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 n-alkanes 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.

Combination of long-chain alcohols and fatty acids with alkanes as faecal markers to estimate feed intake and digestibility in horses and cattle fed on grass-heathland vegetation communities

Application of long-chain alcohols (LCOH) and long-chain fatty acids (LCFA) combined with alkanes as faecal markers to estimate dry matter intake (DMI) and dry matter digestibility (DMD) of equines and cattle was assessed. Six crossbred mares, randomly divided in two groups (H1 and H2), and three nonlactating cows (C) were housed in individual stalls. Groups H1 and C were fed on a diet of ryegrass (Lolium perenne, 0.7) and heather (Erica spp., Calluna vulgaris, 0.3), and H2 received ryegrass (0.4), heather (0.3) and gorse (Ulex gallii, 0.3). Digestibility was estimated using LCOH (C28-OH and C30-OH) and LCFA (C28-FA, C30-FA, and C32-FA) as internal markers. For DMI estimation, animals received daily a paper pellet containing C24, C32, and C36n-alkanes. Intake was estimated from the faecal ratio of naturally occurring LCOH, LCFA, and dosed n-alkanes, and was compared with the known DMI values. In horses, all markers provided accurate estimates of DMD. Similarly, LCOH provided accurate estimates of DMD in cattle, whereas LCFA underestimated it (P < 0.05). Intake estimates were affected (P < 0.05) by the marker pair used in calculations. In general, the C24:C24-FA pair provided the most accurate DMI estimates. Results suggest the usefulness of combining epicuticular compounds as faecal markers to estimate DMI, DMD and diet composition of horses and cattle grazing grass-heathland communities, simultaneously.