P. Bijma et Ja. Woolliams, Prediction of genetic contributions and generation intervals in populations with overlapping generations under selection, GENETICS, 151(3), 1999, pp. 1197-1210
A method to predict long-term genetic contributions of ancestors to future
generations is studied in detail for a population with overlapping generati
ons under mass or sib index selection. An existing method provides insight
into the mechanisms determining the flow of genes through selected populati
ons, and takes account of selection by modeling the long-term genetic contr
ibution as a linear regression on breeding value. Total genetic contributio
ns of age classes are modeled using a modified gene flow approach and long-
term predictions are obtained assuming equilibrium genetic parameters. Gene
ration interval was defined as the time in which genetic contributions sum
to unity, which is equal to the turnover time of genes. Accurate prediction
s of long-term genetic contributions of individual animals, as well as tota
l contributions of age classes were obtained. Due to selection, offspring o
f young parents had an above-average breeding value. Long-term genetic cont
ributions of youngest age classes were therefore higher than expected from
the age class distribution of parents, and generation interval was shorter
than the average age of parents at birth of their offspring. Due to an incr
eased selective advantage of offspring of young parents, generation interva
l decreased with increasing heritability and selection intensity. The metho
d was compared to conventional gene flow and showed more accurate predictio
ns of long-term genetic contributions.