Development of equations to predict in situ rumen degradation characteristics of NDF in maize silages

In a 2021 study for Centraal Veevoederbureau (CVB) equations were updated to predict in situ rumen degradation of crude protein and starch in maize silages. However, the equations for neutral detergent fibre (NDF) were not updated. The present study therefore established new prediction equations for rumen NDF degradation characteristics using pooled data (n = 181) from the CVB archive, GSSP, ILVO and SFR datasets. Stepwise regression showed that the in situ rumen undegradable NDF fraction was best explained by total tract organic matter digestibility, whereas the in situ rumen fractional degradation rate was unrelated to nutrient composition. Adopting the new equations that were developed in this study and a revised rumen fractional passage rate of NDF of 1.25%/h substantially increases estimated rumen-fermented NDF and the calculated amount of rumen formed microbial protein supply as a consequence of an increase in rumen fermented NDF.