The response of continuously stocked sptingcalving beef cows and calves to a range of sward surface heights was determined. Mean sward heights of 4-5, 60, 70, 9 1 and II 0 cm (treatments A to E respeclively) were maintained from mid-May to mid-August (Period I) and treatments C, D and E continued until the end of September (Period 2), during which time mean sward heights were 5-4, 7-8 and 92 cm respectively. Hereford x Friesian or White Shorthorn-X Galloway cows with their Charolais-cross calves were used, with 9, 6, 6, 5 and 9 cows on treatments A to E respectively. During Period 1 the mean liveweight gains of cows were -0-52, -0 05,0-32,0 75 and0 40 (s.e.d. 0167) kgd"' on treatments A to E respectively and during Period 2. -0-31, 057 and 0 59 (s.e.d. 0153) kgd-' for treatments C, D and E respectively with maximum cow liveweight gain at sward heights of 8 to 10 cm. Calf liveweight gains were 0 88,0 91,0 98, 1 04 and 1 06 (s.e.d. 0 068) kg d -' in Period 1 for treatments A to E respectively and 0 98, I -22 and 1 35 (s.e.d. 0067) kg d"' in Period 2 for treatments C, D and E. The percentage of area infrequently grazed was generally less than 20% on treatments A to D, but on treatment E it was more than 40% for 6 weeks after turnout and thereafter remained between 20 and 40%. Maximum calf liveweight gain per hectare was achieved on the shorter swards, but maximum Correspondence: Dr I. A. Wright, Macaulay Land Use Research Institute, Penlliind field, RosUn, Midlothian, EH26 OPY.total liveweight gain of cows and calves per hectare occurred on treatment D. It is concluded that for maximum cow and calf performance on continuously stocked pastures, sward height should be maintained at no more than 8 cm in spring and early summer and then increased to 9 to 10 cm later in the grazing season.
