Lifetime (seven years) production of 1/4 and 1/2 Finnish Landrace ewes from Rambouillet, Targhee and Columbia dams under range conditions.

Lifetime lamb and wool production of 1/4 and 1/2 Finnish Landrace (Finn) crossbred ewes in comparison with local purebred controls was evaluated under range conditions. A total of 1,234 ewe lambs, representing nine breed groups, were first exposed to breeding at 7 mo of age and subsequently retained with no artificial culling, except for debilitating unsoundness, through 7 yr of production. Mating was to Suffolk sires. Differences among pooled breed groups (1/4 Finns, 1/2 Finns and purebreds) generally were not significant for ewe viability to lambing, percentage of lambs born alive and lamb viability to weaning; nor were differences significant for fertility except among yearlings (12 mo at lambing) where 1/4 and 1/2 Finn fertility exceeded that of purebreds by 217 and 278%, respectively. However, for prolificacy, Finn-crosses were consistently superior to purebreds at all seven ages; 1/4 and 1/2 Finns averaged 24 and 48% higher, respectively, than purebreds. Further, Finn-cross ewes clearly excelled purebreds (P less than .05) in the two overall measures of reproduction--net reproductive rate and weight of lamb weaned. The superiority was sustained through all ages and averaged (over ages 2 through 7 yr) 29 and 49% for net reproductive rate and 24 and 41% for weight weaned, for 1/4 and 1/2 Finns, respectively. Conversely, for wool weight, purebreds were consistently superior at all ages; the lifetime averages of 1/4 and 1/2 Finn fleeces were only 90 and 77% as high, respectively, as those of purebreds. It was concluded, however, that the loss in value of wool production associated with Finn breeding was economically of much less importance than the gains made in weight of lamb weaned. The use of 1/4 and 1/2 Finn-crosses involving the above adapted domestic breeds increased the net value of lifetime production by approximately 18 and 29%, respectively.