Lignin in feed as digestibility and digesta transit marker in pig studies

Increased use of lignocellulosic side- or waste-streams in animal diets demands more knowledge on the fate of dietary fibres in the gastrointestinal tract and their effect on digestion and intestinal health of (monogastric) animals, such as pigs. To obtain more insights in the fate and nutritional value of such fibre-rich diets, field studies aiming at digestibility mapping under practical conditions need to be performed. Yet, such studies demand a suitable marker. In this research we evaluated the ‘accepted’ (structural) inertness of intrinsic feed lignin throughout the pig's gastrointestinal tract, as well as its potential as a marker to estimate nutrient digestibility and digesta transit in pigs. To this end, we performed thorough method optimisation and validation, allowing quantification of lignin in complex (faeces and digesta) matrices.