Predicting N-alkane Concentration in Pastures and Deer Faeces for Dietary Composition and Digestibility Measurement Using Near Infrared Spectroscopy

The alkanes in plant materials can potentially be used as markers to estimate composition and digestibility of diet of deer for the development of feeding strategies, but the analysis of alkanes in plant materials and deer faeces is time-consuming and expensive. In this study, 242 faecal samples and 119 pasture samples were scanned using near infrared spectroscopy (NIR) and the concentrations of alkanes in these samples were analysed to develop calibrations for predicting alkane concentrations in pastures and deer faeces. The $R^2$ values for NIR calibrations were <0.6 for $C_{24}$, $C_{26}$, $C_{32}$ and $C_{36}$, but were >0.8 for other alkanes for faecal samples. The $R^2$ values were >0.87 for alkanes with chains from $C_{27}$ to C35 for pasture samples. However, NIR was unable to predict concentrations of alkanes with chains of $C_{24}$, $C_{26}$, $C_{32}$ and $C_{36}$ in faecal samples and $C_{24}$, C25, $C_{26}$ and $C_{36}$ in pasture samples. While the use of these NIR calibrations will accelerate the estimation of diet digestibility, dietary components and botanical composition of pastures, the influence of the type of pasture on NIR calibration will require further examination.