Animal Husbandry practices in the production of fat lambs in the Imperial Valley of California are quite different from those in the remainder of the state. Shipment of feeder lambs into the Imperial Valley begins early in September and is usually completed by the end of October. The lambs are grazed inside temporary fencing on alfalfa and barley stubble pastures. Pastures of 80 acres are usually used, and a band of 1,500 to 2,000 lambs is grazed for 1 to 2 weeks, after which the lambs are driven or trucked to another pasture. Dry hay is occasionally fed as supplemental feed. Most shearing is done by the middle of December, and most of the lambs are marketed directly from pasture by the first of March. In view of these husbandry practices, different patterns in the host-parasite relationship might be expected between sheep and their gastrointestinal nematode (roundworm) parasites in the Imperial Valley than in other regions of the state.