Silage and milk production: a comparison between unwilted and wilted grass silages

Three grass silages made in sunny weather in early July from second‐harvest perennial ryegrass were compared in a 16‐week feeding experiment with twelve Ayrshire cows. The silages were either unwilted or wilted with and without conditioning, and had mean dry matter (DM) concentrations of 201, 261 and 272 g kg−1, and in vitro DOMD concentrations of 650, 669 and 672 g kg−1 DM respectively. All the silages had formic acid (‘Add‐F’) applied at a rate of 2.6 litres t−1 and were offered ad libitum plus 6 kg concentrates per cow per d. The daily intakes of silage DM were 905 kg per cow on the unwilted treatment and 9.86 and 9.65 kg on the wilted treatments with and without conditioning respectively. Daily milk yields were 171, 17.6 and 17.4 kg per cow on the unwilted, and wilted with and without conditioning treatments respectively and were not significantly different. Fat concentrations in the milk were not affected significantly by treatment, whereas the crude protein and solids‐not‐fat concentrations were significantly higher on the wilted than on the unwilted treatment. The efficiency of utilization of metabolizable energy for lactation was 6–7% lower with the wilted than with the unwilted silages and it is concluded that the unwilted silage was superior to the wilted silages as a feed for dairy cows.