In hill sheep systems, a major concern for health and welfare is for lambs grazing improved land at higher stocking rates and succumbing to parasitic gastro-enteritis. With only a small amount of improved land available, there is little or no scope for ‘clean grazing’ systems as access to this better land is crucial on an annual basis to achieve better performance from the flock. Access at lambing and at ewe mating is of particular value. There may however be some scope for reduced parasitic challenge to lambs during the summer grazing period because of the differential in stocking densities between the hill and the improved grazings.