Effects of Substituting Finnsheep and Dorset Breeding for Rambouillet Breeding II. Productivity of Fall-Lambing Ewes

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Abstract
The main effects of increasing Dorset and Finnsheep breeding by ¼ at the expense of Rambouillet breeding on ewe productivity traits of crossbred ewes when lambing in the fall of 1974 and 1975 at ages ranging from 2½ to 4½ years were estimated. Two-hundred-eight crossbred ewes representing four combinations of Finnsheep (F), Dorset (D) and Rambouillet (R) breeding (½D½R, ¼D¾R, ¼F½D¼R and ¼F¼D½R) started the study. The comparison of the ½ Dorset ewes with the ¼ Dorset ewes estimated the main effect of increasing Dorset breeding by ¼ at the expense of Rambouillet breeding (¼ Dorset effect) and the comparison of the ¼ Finnsheep ewes with the 0 Finnsheep ewes estimated the main effect of increasing Finnsheep breeding by ¼ at the expense of Rambouillet breeding (¼ Finnsheep effect). The ¼ Finnsheep effect resulted in little change in ewe breeding weights and a decrease (P<.01) in grease fleece weights both years. The ¼ Dorset effect resulted in a decrease (P<.01) in ewe breeding weights and grease fleece weights both years. The ¼ Finnsheep effect on kilograms of lamb weaned per ewe exposed was negative in both 1974 and 1975 (−2.5 kg and −6.4 kg, P<.05; respectively) due largely to a smaller proportion of the ¼ Finnsheep ewes lambing than the 0 Finnsheep ewes in both 1974 and 1975 (14.1%, P<.05 and 24.9%, P<.01; respectively). In both years, the ¼ Dorset effect resulted in little change in kilograms of lamb weaned per ewe exposed. Copyright © 1979. American Society of Animal Science . Copyright 1979 by American Society of Animal Science.