Effect of swath treatment on water loss during field-wilting and on feeding value of perennial ryegrass silage

The effect of spreading mown perennial ryegrass (Lolium perenne) herbage over the total ground area on water loss during field-wilting was compared with leaving herbage in swaths (three swaths put together into one, occupying 0·18 of ground area) in three experiments. Spread crops were not tedded during wilting but were rowed up immediately before harvest. In all experiments, conventional silage-making equipment was used on a field scale. Feeding value was assessed with lactating dairy cows and growing heifers (Experiment 1) and sheep (Experiment 3). The periods of field wilting were 48 h (Experiment 1), 24 h (Experiment 2) and both 24 h and 48 h (Experiment 3). Spreading the crop was associated with larger increases in loss of water in all three experiments compared with leaving grass in swaths. Losses of dry matter (DM) during wilting were similar in Experiment 2 but were higher for the swathed crop wilted for 48 h than for 24 h in Experiment 3. Spreading resulted in restricted fermentations associated with higher crop DM contents at ensiling. In Experiment 1 the concentrations of DM, ash and water-soluble carbohydrate in silage were higher (P < 0·001) for spreading the crop and the concentrations of crude protein and neutral-detergent fibre were lower (P < 0·05) than for swathed material. In Experiment 3, spreading was associated with higher concentrations of water-soluble carbohydrates and ethanol and lower concentrations of fermentation acids, ammonia-N and neutralizing value in silage. Voluntary DM intake of silage by dairy cows and heifers was higher for spread than for swathed material (P < 0·05), but in Experiment 3 (sheep) there were no significant differences between treatments in voluntary intake of DM. The increased intake by dairy cows of silage from spread herbage was reflected in increased concentrations of milk fat (P < 0·01) and protein (P < 0·05) but not in milk yield (P > 0·05). It is concluded that spreading herbage during field wilting prior to ensiling accelerates water loss and has the potential to improve the feeding value of the ensiled product.