Lucerne grazing management 2. Effect of grazing duration on defoliation pattern by ewes

Patterns of defoliation of lucerne (Medicago sativa L.) by sheep were compared during 12-day and 3-day grazing durations at stocking densities calculated to consume the available herbage in the specified grazing duration. Sheep grazing for 12 days ate more of the available herbage than sheep grazing for 3 days. The difference arose in the early stages of the long grazing duration when the lower grazing pressure resulted in a higher per head allowance of the most palatable plant parts, the apices and leaves, which resulted in a 29% higher intake initially. For both grazing durations the rate of herbage consumption declined during grazing because of a decline in herbage mass and an increase in the proportion of lower digestibility stem material. The in vitro digestibility of the leaf-less stalk at the end of grazing for 12 days was equivalent to lucerne hay, herbage on offer having declined 20% in digestibility since the start of grazing. These findings suggest that high liveweight gain in animals would be favoured by 12-day rather than 3-day grazing, but once leaf and upper stem of lucerne is consumed, the lower stem should be utilised by stock that only require maintenance feeding.