Concept note: in vitro multi-enzyme approach to estimate crude protein and amino acid digestibility in grains for broilers

The knowledge of the precaecal digestibility of crude protein (CP) and amino acids (AA) has gained importance. However, since animal welfare is given high priority, animal digestibility experiments are recommended to be reduced or replaced. Thus, in vitro approaches are of interest for feed evaluation. The present study aimed for an adaption of a multienzyme assay. An in vitro assay to predict the precaecal digestibility of CP and AA in feedstuffs for swine was adapted to predict the standardised precaecal digestibility of CP and AA quickly in feedstuffs for broilers. In the adapted in vitro assay, the conditions of the gastro-intestinal tract of chicken were simulated in three steps, representing the crop, the stomach, and the small intestine. Samples were incubated at 41 °C for 30 min in a buffer solution at pH 6.0, for 135 min with pepsin at pH 2.6 and for 120 min with pancreatin at pH 6.4. The in vitro rate of CP disappearance of nine different cereal and legume grains was related to their standardised precaecal CP and AA digestibility previously determined in broiler chicken. Regressions between the in vitro rate of CP disappearance and the precaecal digestibility of CP for 42-day old broiler chicken had high coefficients of determination (R2 = 0.89). The adapted method has the potential to predict the precaecal digestibility of CP and AA in feedstuffs for broilers. An extension of the calibration using further samples of single and mixed feed with known precaecal digestibility of CP and AA is recommended.