Evaluation of long-chain alcohols as diet composition markers in goats grazing heathland areas

Choices between red clover and fescue in the diet can be reliably estimated in heifers post-weaning using n-alkanes

Measuring diet choice in grazing animals is challenging, complicating the assessment of feed efficiency in pasture-based systems. Furthermore, animals may modify their intake of a forage species depending on its nutritive value and on their own physiological status. Various fecal markers have been used to estimate feed intake in grazing animals. However, plant-wax markers such as n-alkanes (ALK) and long-chain alcohols may provide reliable estimates of both dietary choices and intakes. Still, their use in beef cattle has been relatively limited. The present study was designed to test the reliability of the ALK technique to estimate diet choices in beef heifers. Twenty-two Angus-cross heifers were evaluated at both post-weaning and yearling age. At each age, they were offered both red clover and fescue hay as cubes. Following 3-week acclimation periods, daily intake of each forage species was assessed daily for 10 days. During the final 5 days, fecal grab samples were collected twice daily. The ALK fecal concentrations were adjusted using recovery fractions compiled from literature. Diet composition was estimated using two statistical methods. Post-weaning, dietary choices were reliably estimated, with low residual error, regardless of the statistical approach adopted. The regression of observed on estimated red clover proportion ranged from 0.85±0.08 to 1.01±0.09 for fecal samples collected in the p.m. and for daily proportions once averaged, respectively. However, at yearling age, the estimates were less reliable. There was a tendency to overestimate the red clover proportion in diets of heifers preferring fescue, and vice versa. This was due to greater variability in ALK fecal concentrations in the yearling heifers. Overall, the ALK technique provided a reliable tool for estimating diet choice in animals fed a simple forage diet. Although further refinements in the application of this methodology are needed, plant-wax markers provide opportunities for evaluating diet composition in grazing systems in cattle.

Faecal biomarkers can distinguish specific mammalian species in modern and past environments

Identifying the presence of animals based on faecal deposits in modern and ancient environments is of primary importance to archaeologists, ecologists, forensic scientists, and watershed managers, but it has proven difficult to distinguish faecal material to the species level. Until now, four 5β-stanols have been deployed as faecal biomarkers to distinguish between omnivores and herbivores, but they cannot distinguish between species. Here we present a database of faecal signatures from ten omnivore and herbivore species based on eleven 5β-stanol compounds, which enables us to distinguish for the first time the faecal signatures of a wide range of animals. We validated this fingerprinting method by testing it on modern and ancient soil samples containing known faecal inputs and successfully distinguished the signatures of different omnivores and herbivores.

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.

Use of n-alkanes for determination of Kikuyu grass (Pennisetum clandestinum) intake in free-range broilers

N-alkanes, long-chained saturated hydrocarbons occurring in plant cuticles, were used for estimating grass intake in fast-growing, free-range broilers. A total of 1440 as hatched mixed sex Cobb 500 broilers were equally divided between one of four experimental treatments in a 2 by 2 factorial arrangement involving conventional (barn) or free-range (barn and range access) production systems and diets (crude protein: 21%, metabolisable energy: 13 MJ/K) with or without in-feed antibiotic (Zinc Bacitracin: Albac® G 150 antibiotic feed premix, Pfizer Australia Pty Ltd, Sydney, NSW, Australia). Day-old chicks were randomly allocated to 48 pens (12 replicates/treatment) with 30 birds in each pen. Chicks were assigned to treatment diets on Day 1 while free-range access was available to birds from Day 21 onwards. Alkane concentrations in litter were measured and compared with alkane profiles of the intake components (grass, diet pellets and woodchip). Correction for incomplete recovery followed by estimation using a non-negative least square procedure resulted in calculation of total grass intake from the range area. Kikuyu grass consumption was estimated to be 13.5–14.7% of total ‘as-fed’ intake, equating to 6.34–6.78 g of grass per bird per hour of range access in this study. Taking into account grass consumption, this resulted in a significant increase in feed intake by 8.7–8.9% (P < 0.01) and feed conversion ratio from 2.30 to 2.54 points (P < 0.01). It can be concluded that broilers reared under free-range conditions eat a substantial quantity of grass. However, the nutrient profile of grass is not complementary to the formulated ration and its consumption is likely to lead to an array of nutritional changes for the bird, thus affecting performance.