When Less May Mean More: Studies on Range Versus Shed Lambing In a Cold Desert Shrub Ecosystem

Abstract

Range lambing was compared with shed lambing using 235 3/4 Targhee × 1/4 Finnsheep mature ewes. Pregnancy diagnosis was done with a realtime ultrasound unit 75 d after ram removal. Based on the estimated number of fetuses, ewes were assigned to either a shed or range lambing treatment group using a stratified random procedure. Ewes in the shed lambing group were given assistance as necessary and were placed in lambing pens for 2 to 3 d, then moved to mixing pens for a minimum of 3 d. Ewes in the range lambing treatment were placed on pasture approximately 12 d before lambing and were not disturbed until the average lamb age was approximately 25 d. Shed lambing increased the percentage of live lambs by 21 percentage units at 25 d of age compared to the range lambing group. This difference was largely due to increased survival of lambs from multiple births. The difference between lambing treatments was reduced to 5 percentage points by weaning. Lambs from the range lambing group were .9kg heavier at 25 d of age (P<.09) and 1.4kg heavier at weaning (P<.02). There was no difference in kilograms of lamb weaned per ewe, with the increased lamb survival in the shed lambed group offset by the heavier lamb weights in the range lambed group. Ewe death losses were higher (P<.11) in the range lambing group. Ewe weights were 5.4kg heavier (P<.001) at 25 d postlambing in the range lambing group and 1.9kg heavier at weaning. Results indicate that producers that have shed lambing facilities and want to maximize lamb crop should use pregnancy diagnosis and shed lamb ewes with multiple lambs and range lamb ewes with single lambs. However, producers that want to maximize net income should range lamb all ewes.