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Genetic and Environmental Effects on Age at First Estrus and on Wool and Lamb Production of Crossbred Ewe Lambs^{1 ,2,}

Oregon State University, Corvallis 97331 and and Montana State University, Bozeman 59715

Abstract

Genetic and environmental factors affecting age of first estrus, wool production, reproduction and lamb production were examined in crossbred ewe lambs from 2 birth years. The 399 ewe lambs were from eight crossbred groups resulting from mating North Country Cheviot, Dorset, Finnsheep and Romney rams to Suffolk or whiteface, Columbia-type range ewes. The ewe lambs were raised to weaning on western Oregon hill pastures. They were summered and maintained through the breeding season on irrigated pastures. After mating they were equally and randomly divided within crossbred groups to irrigated or to hill pasture environments.

Average age at first estrus for the 90% of ewes which did cycle their first fall was 205 days. Sire breed and the sire x dam breed interaction were not significant effects, but ewes with Suffolk dams cycled 10 days earlier than ewes with Columbia dams (P<.01).

Breed of the ewe's dam affected wool grade (P<.01) with Columbia crosses having finer wool. Columbia breeding caused longer staple length than Suffolk breeding in all groups except Romney crossbred ewes (sire x dam breed interaction, P<.05). Grease fleece weight from Columbia crosses was consistently heavier than that from Suffolk crosses (P<.01). Romney sired ewes had the heaviest fleeces followed by Cheviot, Dorset and Finn sired ewes (P<.01).

Fertility and prolificacy of ewes with Finn sires were superior to those of ewes with Dorset, Cheviot or Romney sires; while ewes with Suffolk dams averaged higher in fertility than ewes with Columbia dams. Finn cross ewes excelled for total weight of lamb weaned, followed by Dorset, Cheviot and Romney sired ewes (P<.01). The greater lamb production of the Suffolk cross ewes (P<.01) more than compensated for their lower wool production.

Birth year influenced age at first estrus (P<.01) and several wool and lamb production traits, but management environment influenced neither lamb or wool production.

¹ Technical Paper No. 4354, Oregon Agricultural Experiment Station and Technical Paper No. 716, Montana Agricultural Experiment Station.

² Financial assistance from Pendleton Woolen Mills, Portland, Oregon, for wool evaluations is gratefully acknowledged.

³ Department of Animal Science, Oregon State University.

⁴ Wool Laboratory, Montana State University.