Optimal mass selection policies for schemes with overlapping generations and restricted inbreeding

Optimum breeding schemes for maximising the rate of genetic progress with a restriction on the rate of inbreeding (per year or per generation) are inv estigated for populations with overlapping generations undergoing mass sele ction. The optimisation is for the numbers of males and females to be selec ted and for their distribution over age classes. Expected rates of genetic progress (Delta G) are combined with expected rates of inbreeding (Delta F) in a linear objective function (Phi = Delta G-lambda Delta F) which is max imised. A simulated annealing algorithm is used to obtain the solutions. Th e restriction on inbreeding is achieved by increasing the number of parents and, in small schemes with severe restrictions, by increasing the generati on interval. In the latter case the optimum strategy for obtaining the maxi mum genetic gain is far from truncation selection across age classes. In mo st situations, the optimum mating ratio is one but the differences in genet ic gain obtained with different mating ratios are small. Optimisation of sc hemes when restricting the rate of inbreeding per generation leads to short er generation intervals than optimisation when restricting the rate of inbr eeding per year.