The effect of field wilting and mechanical treatment on the feeding value of grass silage for beef cattle and on beef output per hectare

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Abstract
Two experiments were carried out to compare three methods of harvesting grass silage for beef production. These involved (a) harvesting the grass directly with a flail forage harvester (b) pre-cutting the grass with a rotary mower and harvesting it with a precision-chop forage harvester without wilting and (c) pre-mowing and harvesting with a precision-chop forage harvester after field wilting for 36 to 80 h (experiment 1) or 20 to 24 h (experiment 2). Half of the grass harvested by each method received formic acid at a rate of 2·5 1/t while the other half received no additive. The silages were offered ad libitum and supplemented with 2·6 kg concentrates per head daily to 72 castrated male cattle in each experiment. The unwilted and wilted herbages had mean dry-matter concentrations of 163 and 273 g/kg at ensiling and all silages were well preserved. Harvesting silage with a precision-chop rather than a flail forage harvester produced only a small non-significant increase in intake (0·034) and performance (0·046) and did not affect carcass gain per ha. Field wilting for 36 to 80 h prior to ensiling (experiment 1) reduced animal performance by 0·08 and beef output per ha by 0·11. Wilting for 20 to 24 h in ideal weather (experiment 2) did not affect animal performance or beef output per ha compared with that produced by well-preserved, unwilted silage. There was no significant interaction between method of harvesting and additive treatment.