ASSESSMENT OF CONTRASTING PERENNIAL RYEGRASSES, WITH AND WITHOUT WHITE CLOVER, UNDER CONTINUOUS SHEEP STOCKING IN THE UPLANDS .3. HERBAGE PRODUCTION, QUALITY AND INTAKE

Herbage characteristics were monitored over 3 years (1985-1987) in three perennial ryegrass (Lolium perenne L.) varieties as grass/only (200 kg N ha-1) and grass/clover (Trifolium repens L.) (75 kg N ha-1) swards when continuously stocked with sheep. Although mean total annual herbage production was similar from the grass varieties, growth of Aurora, a very early-flowering variety, was higher than that of Aberystwyth S23 and Meltra (tetraploid) late-flowering types in spring. Herbage production from grass-only swards was 15% higher than from grass/clover swards. In vitro organic matter digestibility (OMD) of Aurora and Meltra was 34 g kg-1 and 26 g kg-1 higher (P < 0.01) than that of S23. Averaged over varieties, the OMD of grass/clover was 25 g kg-1 higher (P < 0.05) than grass-only during the post-weaning period. Individual lamb digestible organic matter intake (DOMI) was 22% higher (P < 0.05) on grass/clover than on grass-only during this period. Water-soluble carbohydrates content of Aurora was 42% higher (P < 0.001) than that of both Meltra and S23. Herbage characteristics were related to lamb performance reported previously. Lamb production was positively correlated with DOMI. However, the magnitude of differences in lamb performance between treatments was much greater than the extent of differences detected in herbage characteristics.