Gas production kinetics in predictions of voluntary intake of grass silage by cattle

The objective of this study was to predict voluntary intake by cattle of grass silages of different fermentation quality from in vitro gas production data. Further, biological concepts of intake related gas data were examined by cluster analysis to silage chemical composition. Samples from 24 grass silages were characterized from their gas profiles. Observed silage dry matter intake was modelled by partial least squares regression analysis. Cumulative gas volumes and rates of gas production during early incubation, asymptotic gas volume as well as discrete lag time, and cumulative gas volumes at 48 and 72 h were the best descriptors of the variation in silage intake. The discrete lag time had a strong negative influence on intake and made up clusters with chemical variables indicating secondary fermentation. In vitro gas production data did not improve silage dry matter intake predictions compared with current models based on chemical analysis of silage fermentation quality.