By using separated values of kinetics of in situ dry matter (DM) degradation or in vitro gas production (Menke and Steingass, 1988) of leguminosae hays, Khazaal et al, (1993) reported high correlation with intake (r= 0.88; r= 0.79) and in vivo DM digestibility (DMD) (r= 0.94; r= 0.88). The aim of the present study was to extend the range of samples used and compare the ability of the 2 stages in vitro digestibility (Tilley and Terry, 1963), the in situ DM degradation or the gas production techniques to predict daily intake (g DM/ kgW0.75) and in vivo DM digestibility (DMD) of 19 leguminous and graminaceous hays fed to sheep.
Three harvesting stages (early bloom EB, mid bloom MB or in seed IS) made from lucerne (Medicago sativa), sweet clover (Melilotus segetalis), Persian clover (Trifolium resupinatum), Rye (Secale cereale), Triticale (Triticale hexaploid), oat (Avena stativa) and a pre-bloom (PB) Italian ryegrass (Lolium multiflorum ). Each hay was fed ad libitum to 4 Merino male sheep and their intake and in vivo DMD recorded. Gas production (ml/ 200 mg DM) or in situ DM degradation (g/ 100 g DM) were determined as described by Khazaal et al, (1993) after 6, 12, 24, 48, 72 or 96 h incubation. Measured gas production or DM degradation values were fitted to the equation p=a+b(l-e-ct)(McDonald, 1981) where p is gas production or DM degradation at time t and a, b and c are constants. For nylon bag the washing loss (soluble fraction) was defined as A, the insoluble but fermentable matter was defined as B=(a+b)-A, and c is the rate of fermentation or degradation (Ørskov and Ryle, 1990).