The interaction of internal parasites and nutrition in the utilization of grassland by sheep

Abstract
1. The value of ‘worm-free’ sheep in the assessment of pasture is illustrated by an experiment in which the effect of internal parasites could only be distinguished by the use of ‘worm-free’ controls.2. The effect of augmenting the initial pasture infestation (with nematodes parasitic in the sheep) was slight.3. In an experiment with ewes and lambs at three lambing percentages and over a range of stocking rates: