a1 AFRC Institute of Animal Physiology and Genetics Research, Edinburgh Research Station, Roslin, Midlothian EH25 9PS
The effect of changes in the mating system on the rates of genetic progress and rates of inbreeding are considered for MOET nucleus breeding schemes. Methods are derived to calculate best linear unbiased predictors of breeding value in MOET schemes and the rate of inbreeding under selection. These are applied to different mating systems in which the numbers of sires and dams, and the number of offspring per sire and offspring per dam, remain constant.
Results showed that compared with nested mating systems, factorial mating systems in which the maternal half-sibs are produced instead of full-sibs, could increase genetic progress by 1·12-fold with no additional inbreeding. The increased progress arose through an increase in the selection intensity applied. The rates of inbreeding derived were found to be approximately double those estimated by the formula of Wright (1931) in the absence of selection.
In practice, even if a complete factorial system were to increase the generation interval and consequently reduce progress below that predicted, changes in the mating system avoiding this problem could be implemented that would be of immediate benefit.
(Received August 18 1988)
(Accepted January 29 1989)