Effect of forage hydration on lag time during in vitro digestion of meadow hay

Digestion of plant cell wall has been observed to be a first-order process with an initial lag. Lag is defined as the period of time immediately after forage is exposed to the fermentive environment during which digestion does not occur or occurs at a greatly reduced rate. The effects of forage hydration on lag were investigated by focusing on the first 20 h of in vitro digestion of meadow hay. Samples were hydrated for 0, 1, and 16 h before fermentation. Digestion kinetics was estimated by both a first-order kinetics model (KM) and an increasing relative-rate model (RRM). Model parameters were obtained using a non-linear least-squares procedure. The effect of forage hydration was significant, especially for the 16-h treatment. The RRM produced a better fit for the data from each treatment, and a better fit was obtained when each data set was analysed separately.