Measurement of cell-wall digestibility in lucerne using the filter bag technique
Résumé
A new filter bag technique was tested for the measurement of enzymatic digestibility of cell-wall in lucerne. Breeding for a higher cell-wall digestibility requires its measurement in in vitro conditions on small quantities of forage samples with a low cost, rapid method. Three methods of evaluation of cell-wall digestibility were tested on 60 whole plant samples and 60 stem samples of lucerne and compared. These three methods consisted in 1/ measurement of enzymatic digestibility of cell-wall by incubation of cell-wall residue in enzymatic solutions, 2/ calculation of the ratio between cell-wall content of the sample and cell-wall content of the residue of the enzymatic digestion, and 3/ calculation of the cell-wall digestibility through sample cell-wall content and sample digestibility, assuming a non cell-wall digestibility of 90%. The three evaluations were highly correlated and gave similar ranges of variation. The first method was the most precise but the most time-consuming. However, the third one was precise, and this method was the most rapid. NIRS prediction of all cell-wall digestibility estimates was accurate. The choice between the three techniques for breeding for an improved forage digestibility of lucerne needs further investigations on the genetic variation of this criterion measured by the three methods.