Grazing cycle length and silage supplementation: effects on the performance of lactating ewes with twin lambs

Masham ewes, stocked at 20 ewes ha^?1, reared twins at pasture in 1979 and 1980 and were rotationally grazed around six paddocks. There were three lengths of grazing cycle (18, 30 or 42 d) and the ewes at pasture were either offered silage ad libitum (S) for 8 weeks of lactation or they were not supplemented with silage (N). By feeding silage, S ewes and lambs moved into greater herbage masses (3735 u. 3390 kg organic matter (OM) ha^?1), but there was little effect on net herbage accumulation (10.5 v. 10.0 t OM ha^?1) and herbage intakes per ewe were similar (2.31 v . 2.27 kg OM d^?1) over the 7-month grazing season. During the period of silage supplementation, total intake was 19% higher for S than N ewes, lamb growth rates were slightly higher (280 v . 273 g d^?1) and the ewes lost less weight (?78 v ?96 g d^?1).
For 18-, 30- and 42-d grazing cycles respectively the herbage masses before grazing were 2825, 3620 and 4240 kg OM ha^?1; net herbage accumulations were 9.8, 10.4 and 10.6 t OM ha^?1; mean daily herbage intakes by each unit (ewe+lambs) were 2.22, 2.35 and 2.30 kg OM and lamb growth rates from birth to weaning at 20 weeks were 205, 204 and 204 g d^?1.
Frequent grazing of relatively light herbage masses or infrequent defoliation of heavier herbage masses made little difference to sward or animal performance. It is concluded that, at this stocking rate, different grazing cycles of 18, 30 or 42 d do not affect the performance of lactating ewes.