Selection for reproduction in Rambouillet sheep was begun in 1969. Ewes were randomly divided into 2 lines, a low(L) and a high(H). Rams and ewes were selected within line on the basis of an index of their dams' reproductive rate. In 1972, all remaining foundation ewes removed from L and H and used to establish a random bred control line(C). The mean yearly selection differentials for rams were -.31, .38 and .03 and for ewes were -.08, .07 and -.06 for L, H and C respectively. The regression of cumulative selection differential on year of birth for rams were -.051, .085 and .014 and for ewes were -.065, .048 and -.014 for L, H and C respectively. Response to selection as measured by the regression of the least-squares means for index within line on year of birth was -.013, .022 and- .011 for L, H and C, respectively. The realized heritabilities (hR) within line were .19, .036 and -.13 for L, H and C, respectively.
Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume XII. Biotechnology, selection experiments, parameter estimation, design of breeding systems, management of genetic resources., , 221–226, 1986
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