Four grass silages, namely unwilted and wilted silages each with and without bacterial inoculation, were prepared on each of eight harvesting occasions during the 1994 growing season (Yan et al. 1998). The four silages, made at each harvest, were offered ad libitum to 48 lactating dairy cows in a 2 (control v. additive)×2 (unwilted v. wilted)×8 (harvest (period)) change-over design experiment with 3-week experimental periods. The animals also received 6·9 kg dry matter (DM) of a concentrate supplement daily during the first period and then the allowance of the supplement was reduced by 0·43 kg DM at the start of each subsequent period. The supplement was based on barley, molasses and soyabean meal. The data presented are the mean results obtained across the eight harvests.

No significant interactions were found between inoculation and wilting for silage intake, performance and silage eating behaviour. Inoculation significantly increased milk yield (2·4%, P<0·05) and lactose output in milk (2·3%, P<0·05) across the unwilted and wilted silages. These increases following inoculation in general arose equally from both the unwilted and wilted silages. However, inoculation of either the unwilted or wilted silages had no significant effects on silage DM intake, milk composition, or silage eating behaviour. Wilting significantly increased silage DM intake (20·1%, P<0·001), milk yield (2·8%, P<0·05) and the concentrations (P<0·001) and yields (P<0·01) of both fat and protein across the untreated and inoculant-treated silages. The increases following wilting derived equally from both the untreated and inoculant-treated silages. Wilting also significantly influenced silage eating behaviour with a significant decrease following wilting in number of meals per day (6·5%, P<0·05) and an increase in eating rate (kg DM per eating hour) (29·7%, P<0·001) across the untreated and inoculant-treated silages. These results indicate that inoculation of the unwilted and wilted silages produced similar increases in milk production. Large positive responses in silage DM intake and performance were recorded following wilting with both the untreated and inoculant-treated silages.