Ten hays harvested at three stages (early bloom MB, mid bloom MB or in seed) made from lucerne (Medicago sativaj, sweet clover (Melilotus segetalis), Persian clover (Trifolium resupinatum) and pre-bloom (PB) Italian ryegrass (Lolium multiflorum var.), were offered ad libitum to four Merino male sheep and daily intake (g dry matter (DM) per kg M0·75) and DM apparent digestibility (DMD) were measured. In sacco DM degradation (g per 100 g DM), gas production (ml per 200 mg DM), in vitro digestibility and fibre composition (g/kg DM) of the hays were also studied. Gas production or DM degradation were calculated at 6, 12, 24, 48, 72 or 96 h and their kinetics were described using the equation p = a + b(1 - e-ct). Intake and in vivo DMD of the hays were variable (P < 0·01). Lucerne EB and Persian clover (all stages) had the highest nutritive value, whereas sweet clover (all stages) had the lowest. Apart from neutral-detergent fibre, which was only related to intake (r = -0·68; P < 0·05), chemical components and in vitro digestibility were poorly (P > 0·05) related to animal performance. Between 12 and 96 h incubation, intake and in vivo DMD were better related to DM degradation (r = 0·79 to 0·83; r = 0·61 to 0·77) than to gas production (r = 0·73 to 0·80; r = 0·58 to 0·78). Prediction of intake and in vivo DMD from the (a + b) values did not provide a great advantage over using some of the static values of gas production or DM degradation.Multiple regression using separated kinetics of degradation resulted in highest accuracy for predicting intake and apparent digestibility from gas production (R2 = 0·63; R2 = 0·78) and nylon bag degradability (R2 = 0·77; R2 = 0·89). It was concluded that the gas test has good potentiality as it was capable of predicting not only apparent digestibility, but also intake to a level close to that of the nylon bag technique.

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The study compared using chemical components (i.e. crude protein (CP), neutral- and acid-detergent fibre or lignin (NDF, ADF and ADL) g/kg dry matter (DM), the in vitro digestibility (Tilley and Terry, 1963), the in situ (nylon bag) DM degradation (g/100 g DM) and gas production (ml/200 mg DM) techniques to predict voluntary daily intake (g DM per kg M0.75) and in vivo apparent DM digestibility (DMD) of 10 graminaceous hays individually offered ad libitum to four Merino male sheep. Gas production or DM degradation were determined after 6, 12, 24, 48, 72 or 96 h incubation and their characteristics described using the equation p = a + b (1 – e-ct). Intake and in vivo DMD of the hays were variable and poorly related (r = 0·52; P > 0·05). The in situ DM degradation was significantly (Y < 0·05) related to in vivo apparent DMD at 48 to 96 h incubation (i = 0·76 to 0·75) and to intake at 24 to 96 h (r = 0·71 to 0·75) incubation. However, fibre components, the in vitro digestibility or gas production were either related to daily intake or in vivo apparent DMD, but not to both on the same occasion. Accurate prediction of intake (r = 0·90; P < 0·05) and in vivo apparent DMD (r = 0·88; P < 0·069) were achieved using NDF, ADF, ADL and CP in a multiple regression. Using the (a + b) and the rate (c) of in situ DM degradation, both in vivo apparent DMD (r = 0·77; P < 0·05) and intake (r = 0·83; P < 0·05) were predicted with accuracy. However, using the (a + b) and (c) of gas production, only intake was predicted accurately (r = 0·87; P < 0·01). The lower performance of the gas test was attributed to the small contribution to gas production and higher buffering capacity resulting from protein fermentation. When data of the graminaceous and other data from leguminous hays were combined, the most accurate prediction of both intake and apparent digestibility was by using characteristics of in situ DM degradation followed by those of gas production. The latter was more accurate than using chemical components or the in vitro digestibility. Addition of CP in the multiple regression improved the prediction of intake and in vivo apparent DMD from characteristics of gas production. It was concluded that despite the need to overcome the problem of protein fermentation in the gas test, accurate prediction of both intake and apparent digestibility can be achieved simply from the degradation characteristics of foods.

Neutral and acid detergent fibre (NDF, ADF), lignin, crude protein (CP), total extractable phenols (TEPH), tannins (TETa), condensed tannins (vanillin assay TECTa ; proanthocyanidins TEPAs) in the leaves of spring Phyllirea media (SPRG) or early summer (ESUM) and early autumn (EAUT) Carpinus duinensis, Quercus coccifera and Fraxinus ornus were studied. Gas production (in uitro) and dry matter (DM) degradation (in sacco) were also studied after incubation for up to 96 h. Concentrations of TEPH, TETa, TECTa, TEPAs and the fibre components were variable (P < 0.05) among species and except for CP were not consistently changed with degree of maturity. CP content varied from 705 to 132.9 (g kg-' DM) but was always decreased by 15-25% at maturity, whereas levels of TECTa and TEPAs were increased (P < 0.05) in C duinensis and Q coccifera but not in Fornus ( P > 0.05). Concentrations of phenolics were related negatively but more significantly to gas production than to DM degradation (in sacco). Therefore, the gas test was considered to be more efficient than the nylon bag technique for the identification of feeds with antinutritive factors. Based on their phenolic content and gas production or DM degradation, the nutritive value of P media = F ornus (ESUM and EAUT) > C duinensis = Q coccifera (ESUM) > Cduinensis = Q coccifera (EAUT). It was concluded that the decline in CP with maturity could make nitrogen the factor limiting intake and digestibility. This would be accentuated with an increase in the concentration of phenolics, particularly tannins.

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