Grazing ewes on mature subclover pastures shortly before and during the breeding season was as effective as grazing them on native range pastures and supplementing with alfalfa pellets at a rate of 2 pounds per day. Ewes on both kinds of pasture produced 21% more lambs than ewes grazed on unsupplemented native pastures. The sheep industry has used flushing increasing the nutrition of ewes shortly before and during the breeding season to increase their lambing rate for decades. Studies in the

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... ly 1930s demonstrated that flushing range ewes resulted in a 9 to 18% increase in the number of twin births. Large trials in Australia and New Zealand produced similarly encouraging results. Researchers there divided the flushing phenomenon into two components: the static effect and the dynamic effect. The static effect was the ewe's body weight at conception. The dynamic effect was the weight change that occurred during the flushing period. The New Zealand study reported a 15 to 20% increase in the number of lambs born and indicated approximately 50% of the response was due to the dynamic effect The New Zealand data also indicated a 6% increase in the twinning rate for every corresponding 10 pounds increase in body weight during flushing. There are several factors that govern the amount of increased lambing rate that can be obtained by flushing: the ewe's genetic potential and age, time of breeding season, length of the flushing period, body weight at conception and change in body weight during flushing and breeding. To expand the productivity of the sheep industry, producers must increase the pounds of lamb weaned per ewe exposed to the ram. The most effective way to increase that figure is to enhance the lambing rate. Lambing rates can be increased by genetic selection and /or crossbreeding. Selecting for multiple births within a flock will increase the lambing rate by approximately 2% per year. A more efficient way to increase the lambing rate for the commercial producer is to crossbreed with a breed having a high lambing rate. Research on the Finnsheep breed has concluded that infusing 25% Finnsheep breeding into a flock will result in a corresponding 25% increase in lambng rate. Lambing rates can also be enhanced by flushing. Under California range conditions, the sheep breeding season occurs at the time when forage is rapidly declining in nutritive value. Early studies conducted at the Hopland Field Station indicated that the protein in forage samples obtained by esophageal fistulated sheep dropped from 9.5 to 6.9% between July and September. Another study conducted at the Hopland Field Station indicated that flushing ewes before and during the breeding season can be very beneficial when the protein in native forage falls below the ewe's nutritional requirements. In earlier work at the Hopland Field Station, pastures of subclover and Hardinggrass mowed before maturing and left in swaths for grazing during the flushing period resulted in a 16.3% increase in lambs born compared with native pastures. The disadvantage of mowing is the additional labor required and the equipment cost. Since a nonmowed treatment was not included, the advantage of mowing couldn't be determined. In our study, we compared two flushing systemsa native range supplemented with alfalfa pellets and a dried subclover rangewith a control of nonsupplemented native range. Our study did not define the nutritional elements that led to a response or lack of response. Three treatments We randomized by age 650 grade Targhee ewes, approximately 218 head for each of three years (1986,1987 and 1988) and assigned them to one of six pastures (three treatments replicated twice). The ewes were all 2 to 5 years old, with three or four ages represented in each of the three years. The treatments were as follows: (1) controlgrazing native range only (NR); (2) grazing native range plus supplementation with 2 pounds of alfalfa pellets per day for 16 or 18 days, depending on year, before the rams were introduced and the first 18 days of the breeding season (SNR); and (3) graz-14 CALIFORNIA AGRICULTURE, VOLUME 48, NUMBER 2