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Ewe Lamb Conception as an Indicator of Future Production in Farm Flock Columbia and Targhee Ewes^{1 ,2,}

Oregon State University, Corvallis, 97331 and Eastern Oregon Agricultural Research Center, Union, 9883

Abstract

One-hundred-thirty-nine Columbia and Targhee ewes born during 1966 through 1970 were exposed to Cheviot or Dorset rams at 7 months of age and to rams of the same breed as the ewes in subsequent years. Records for the second, third and fourth production years and for cumulative second through fourth year production were analyzed. Independent variables were ability vs inability to lamb at 1 year of age, breed of ewe, birth year and all possible interactions. Dependent variables were number of lambs born and weaned, kilograms of lamb weaned and grease fleece weight. Analyses were run both on a per ewe present at lambing and on a per ewe entering the experiment basis. Attrition rates for ewes not lambing at 1 year of age were higher than for ewes which did lamb at 1 year of age, but differences between groups in specific causes of death or culling were not apparent. For cumulative production per ewe present at lambing, ewes able to lamb at 1 year of age produced 5.6 kg more lamb and .4 kg less wool than ewes unable to lamb at 1 year of age. For cumulative production per ewe entering the experiment, the early lambing group weaned .84 more lambs and 27.4 more kilograms of lamb than the later lambing group (P<.05) and produced slightly more wool. How effectively the ability to lamb at 1 year of age predicted future production differed between breeds, however. Early lambing Columbias produced 48.9 more kilograms of lamb and 3.7 more kilograms of wool, while early lambing Targhees produced only 5.9 more kilograms of lamb and 1.3 more kilograms of wool than later lambing Targhees.

¹ Technical Paper No. 4505, Oregon Agricultural Experiment Station.

² Contribution to North-Central Regional Project NC-111, Increased Efficiency of Lamb Production.

³ Department of Animal Science, Oregon State University, Corvallis.

⁴ Eastern Oregon Agricultural Research Center, Union.