Front face fluorescence spectroscopy as a rapid non-invasive tool for determining diet composition in free-ranging ruminants

Abstract

Quantification of the diet consumed in free-ranging ruminants is essential to manipulate both agricultural performance and environmental impact. A common non-invasive approach for determining diet composition is based on using long-chain, saturated hydrocarbons (n-alkanes) as markers (Dove and Mayes, 1996). However a major drawback of using this approach is the time and related expense associated with extracting these compounds. Spectroscopic imaging is a rapidly evolving research area, with the potential to provide real-time solutions. Previous applications have shown its ability to detect chlorophyll and its breakdown products in faeces as markers of contamination in carcasses to reduce pathogen load entering the food chain (Ashby et al. 2003). Chlorophyll is ubiquitous in green plants and thus livestock diets. During digestion in the gut, chlorophyll is only partially degraded to coloured and fluorescent intermediates: phaeophytin, chlorophyllide, phaeophorbide and pyrophaeophorbide derivatives of chlorophylls a and b. It is these compounds that are detected by spectral imaging of the faeces, and comparisons of spectral wavelength profiles may provide comparative information about the animals’ diet.