The effect of wilting and short-chopping of grass on the subsequent voluntary intake of silage, and live-weight gain of calves

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Abstract
Four silages were prepared from perennial ryegrass. Half the crop was picked up soon after mowing and the remainder left to wilt for 24 h. Half the unwilted and half the wilted grass was chopped by a forage harvester with its normal complement of knives; the remainder was chopped by a forage harvester with all but two of its knives removed. The ensiled material was offered ad libitum for 80 days as the sole food to 32 British Friesian male castrates initially 14 weeks of age and 111 kg live weight.Wilting raised silage dry-matter content by 31 g/kg fresh weight and gave lower concentrations of acetic acid whilst short chopping gave lower butyric acid. Concentrations of acetic acid, butyric acid and ammonia nitrogen were high on all treatments. Organic matter digestibility was significantly increased by wilting (P < 0·001) and significantly depressed by chopping (P < 0·001). There was no response in dry-matter intake to short chopping, but wilting raised daily intake from 18·4 to 19·9 g silage dry matter per kg live weight (P < 0·001). Live-weight gain was increased from 0·42 to 0·46 kg/day by short chopping (P < 0·05) and from 0·40 to 0·48 kg/day by wilting (P < 0·01)