Factors Affecting Reproduction in Ewe Lambs

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Abstract
The effects of breed and breed-cross, breeding weight, breeding age, condition score at breeding, lambing age and lambing weight on reproductive performance in 565 ewe lambs was studied. Nineteen breed groups were represented. The ewe lambs were exposed to fertile rams from November 9 to December 14. The lambs averaged 216.7±0.5 days of age and weighed 39.7±2.2 kg at the beginning of the breeding period. Mean age and weight at lambing was 379.5±3.2 days and 34.5±0.3 kilograms. Least-squares means are presented for ewes lambing per ewe exposed (71±2%), lambs born per ewe exposed (93±3%), lambs born per ewe lambing (126±2%) and lambs weaned per ewe lambing (91±3%). Breed and breed-cross had a large, significant (P<.01) effect on these lambing traits. Rambouillet-cross and Finn-cross ewes produced more lambs per ewe exposed and more lambs per ewe lambing than the Suffolk, Hampshire, Rambouillet, Dorset, Targhee, Corriedale and Coarse Wool straightbreds. The Finn-cross ewes had significantly (P<.01) more lambs born per ewe exposed and per ewe lambing than the Rambouillet crosses, 134 compared to 75% and 161 compared to 102%, respectively. A small increase in ewe age at breeding significantly (P<.01) increased number of ewes lambing and number of lambs born per ewe exposed. An increase in ewe age increased lamb birth weight and lambing difficulty. Conditions and body weights of the ewe lambs at the beginning of the breeding season and weight at lambing did not affect any of the reproductive traits studied. Copyright © 1972. American Society of Animal Science. Copyright 1972 by American Society of Animal Science

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