The herbage intake and performance of autumn-calving beef cows and their calves when grazing continuously at two sward heights

Abstract

ABSTRACTThirty-nine Hereford × Friesian autumn-calving cows (mean calving date 17 September) and their Charolais-cross calves were used in a 2 × 2 × 2 factorial experiment to assess the effects of feeding level in winter and sward height in summer on intake and performance. Mean estimated metabolizable energy intakes during winter (30 October to 6 May) were 63 (L) or 92 (H) MJ/day. Two sward heights, 4·8 (SI) or 7·6 (Tl) cm, were imposed from turn-out to weaning on 3 July, and a further two sward heights, 4·7 (S2) or 8·0 (T2) cm, from weaning to housing on 1 October. At turn-out the H cows were 17 kg heavier (P > 0·05) than the L cows and their calves were 30 kg heavier (P < 0·01). Cow herbage intakes were significantly higher on the Tl and T2 treatments compared with the SI and S2 treatments as were live-weight changes: 0·94 v. –0·01 kg/day (P < 0·001) for Tl and SI treatments and 0·96 v. –0·18 kg/day (P < 0·001) for T2 and S2 treatments respectively. Calves on the Tl treatment had higher live-weight gains than those on the SI treatment (1·40 v. 0·63 kg/day; P < 0·001). After weaning the SI cows had significantly higher herbage organic matter intakes than the Tl cows (P < 0·05) and had significantly higher live-weight gains (0·51 v. 0·28 kg/day; P < 0·05). Calving difficulty and calf birth weight were not affected by any of the treatments. The results demonstrate that both previous and current level of nutrition have an effect on cow performance. When cows are turned out to pasture at body condition scores of 2·25 to 2·5, the sward heights recommended for spring-calving cows are equally appropriate for autumn-calving cows.