Grass plots, designed to provide 4 days grazing for three heifers, were divided into four equal sub-plots which were dressed with cow slurry in March at rates between 0 and 100 t/ha. The heifers were put into the plots 7 and 13 weeks after slurry application and were able to choose in which of the sub-plots they spent their time and grazed.
The main effect of slurry on the pasture at 7 weeks was to increase the height of the sward but to decrease herbage dry-matter production. Herbage dry-matter utilization over the 4 days ranged from 94% on the no-slurry sub-plot to only 41% when slurry had been applied at 100 t/ha. The heifers spent most time in and grazed more often in sub-plots with little or no slurry for the first 2 days, but as the grass was eaten down the frequency of grazing on areas with more slurry increased. This was reflected in the amount of grass removed by the heifers from each treatment on each day.
At the beginning of the second grazing, grass height and herbage dry-matter production were both directly related to level of slurry application. The heifers did not distinguish between treatments up to 50 t/ha, but herbage utilization on the 100 t/ha sub-plot was reduced.