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Factors Influencing Reproduction in Ewe Lambs¹

University of Wyoming, Laramie 82070 and U. S. Department of Agriculture, Dubois 83423

Abstract

Increasing production efficiency is as much a challenge to producers of livestock as it is in the more mechanical forms of industry. Sheep producers are using rams which have demonstrated high rates of gain and feed efficiency in feedlot performance tests. Researchers are working with nutrition and hormones to increase conception rates, shorten the postpartum interval and increase the frequency of lambing.

Ch'ang (1967) and Hulet, Wiggins and Ercanbrack (1969) have demonstrated that ewe lambs reaching puberty during their first breeding season possess a higher production potential than other ewe lambs even if they are not bred during that first year. Hulet et al. (1969) has also demonstrated that only 10 to 12 % of ewe lambs raised under Western range conditions reach puberty the first year. Ewes bred first as Iambs have been shown to produce more lambs or more kilograms of lamb during their lifetime than ewes bred first at 18 months of age (Bowstead, 1930; Griswold, 1932; Spencer et al., 1942; Longrigg, 1961).

¹ From University of Wyoming and the U. S. Sheep Experiment Station, Sheep and Fur Animal Research Branch. Animal Science Research Division, A.R.S., Dubois, Idaho. This research was supported in part by an NDEA Title IV Fellowship.

² Present address: Department of Animal Science, Chico Stute College, Chico, California 95926.

³ U.S. Sheep Experiment Station, A.R.S., Dubois, Idaho 83423.

⁴ Division of Animal Science, Laramie, Wyoming 82070.

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