Prediction of relative feed value of alfalfa hays harvested at different maturity stages using in vitro gas production

Abstract

In this study the effect of maturity stage on chemical composition, relative feed value (RFV), dry matter digestibility (DMD), dry matter intake (DMI) and in vitro gas production, of alfalfa hays (Medicago sativa) was investigated. The potential of gas production technique to predict relative feed value (RFV) of alfalfa hays was also evaluated. Gas production was measured at 3, 6, 12, 24, 48, 72 and 96 hour incubation times. The maturity had a significant effect on chemical composition, relative feed value and in vitro gas production, of alfalfa hays. With increasing maturity NDF, ADF and ADL increased and CP content, RFV, DMD and DMI decreased. The variation of RFV explained by the gas production ranged from 87.6 to 93.0. The gas production at 12 and 24 h incubation times explained 93.0 and 92.2 % of variation of RFV respectively. The gas production constants "a" and "b", alone or in combination, explained frpm 88 to 99.7% of the variation of RFV. The gas production rate constant "c" explained only 16.5 % of the variation of RFV.