The effects of wilting of grass prior to ensiling on the response to bacterial inoculation. 2. Intake and performance by dairy cattle over three harvests

Abstract

AbstractFour silages (unwilted with and without inoculant, and wilted with and without inoculant) were prepared from perennial ryegrass swards at each of three harvests over the growing season. The four silages from each of the first (primary growth), second (first regrowth) and third (second regrowth) harvests were offered ad libitum to 48 dairy cows during periods 2, 1 and 3 respectively, in a two (control and additive) × two (unwilted and wilted) × three (harvest (period)) change-over design experiment with 8-week experimental periods. The animals also received a concentrate supplement at 7·0, 6·1 and 5·2 kg dry matter (DM) per day in the first, second and third periods respectively. The supplement was based on barley, molasses and soya-bean meal.There were significant interactions between inoculation and wilting across the three harvests on silage DM intake (F<0-01), milk yield (P<0·05), and outputs of fat (P<0·01) and protein (P<0·05). Inoculation had no significant effects on silage intake and milk production across the unwilted and wilted silages. However, within the unwilted silages, inoculation significantly increased silage DM intake by 0·46 kg/day (P < 0·05) and fat yield by 0·032 kg/day (P<0·05). In contrast, within the wilted silages inoculation significantly reduced fat yield by 0·030 kg/day (P < 0·05). Wilting of grass prior to ensiling significantly increased silage DM intake by 0·73 kg/day (P <0·001), milk yield by 0·42 kg/day (P<0·05), fat yield by 0·053 kg/day (P < 0·001) and protein yield by 0·047 kg/day (P < 0·001) across the inoculant-treated and untreated silages. The effects however were mainly derived from the untreated silages as within the inoculant-treated materials the differences in silage intake and milk yield were not significant between unwilted and wilted treatments. The results of the current experiment indicate that wilting with no additive significantly improved silage intake and milk production, but otherwise the improvement was reduced with wilting following inoculation. Inoculation significantly increased silage intake and fat yield when used with the unwilted grass, but it significantly reduced fat yield when used with the wilted grass.