Sward Surface Height (SSH) can be used as a guide for grazing control and recommendations are available for target SSH at various times of the year and at different levels of performance (Hodgson et al 1986).

188 mule ewes with Suffolk cross lambs were allocated to 2 target SSH, 1-6 cm and 6-8 cm. Each treatment was replicated twice and balanced for ewe age, liveweight and condition score and the age, sex and rearing status of the lambs. The areas grazed were under permanent grass (mainly perennial ryegrass) and received 255 kg N/ha applied in 4 dressings with balancing P. and K. The initial stocking rate was 14.7 ewes/ha with 23.2 lambs/ha. SSH was measured weekly using an HFRO swardstlck with 40 readings taken per area. SSH was maintained using a temporary electric fence to adjust the size of the grazing area. Adjustments were made on a pre-set pattern which took into account any difference between current and target SSH and any change in SSH over the previous week. The area adjustments are shown in Table 1.

Lambs were weighed at fortnightly intervals initially and at weekly intervals from the beginning of July. Lambs were drawn for slaughter at constant condition (3L). Ewes were condition scored and weighed at turnout (12th May), 6 weeks after turnout and at weaning (11th August).