Population size and selection intensity effects on long term selection response in mice

Abstract

Long term response to within full sib family selection for increased post weaning gain was evaluated in lines having different effective population sizes (N(e)) and selection intensities (i). Line designations were I4(4), I8(2), I16(2), M4(4), M8(2) and M16(2), where I and M indicate selection of the top 50% and 25%, respectively; 4, 8 and 16 represent the number of parental pairs per replicate and number of replicates is given in parentheses. Realized within full sib family heritabilities (h(R)2) in the first phase of selection (0-14 generations) were larger in 16 pair lines than in 4 and 8 pair lines. In the second phase of selection (>14 generations), h(R)2 declined significantly (P