Effect of different mating designs on inbreeding, genetic variance and response to selection when applying individual selection in fish breeding programs

Abstract

In selection programs, the aim is to produce genetic progress but also to preserve genetic variability. We investigated a simple way to preserve the genetic variability i.e. the choice of appropriate mating schemes, when pedigrees are unknown. We used computer simulations to compare the ability of different mating systems to preserve genetic variability in populations undergoing selection. The model used for data simulation was a simple polygenic additive model which did not take into account maternal effect, inbreeding depression and unbalanced family sizes. The mating systems considered were full factorial, partial factorial, nested and single pair matings. The evolution of additive genetic variability was studied at two different levels of heritability (0.1; 0.5), two different population sizes (1000 or 5000 animals), 30 generations of selection and different combinations of number of sires/number of dams. Results showed that the various mating designs did differ in terms of long-term genetic variability and genetic response. For the same selection pressure, designs which created the highest number of families were the most efficient. Thus, factorial designs were the most efficient and single pair designs were the least efficient. However, differences between full factorial and partial factorial designs were small. When possible, partial factorial mating (FS) designs seemed to be a good compromise to achieve high genetic responses while preserving genetic variability. Further studies dealing with effect of inbreeding depression, maternal effects or unbalanced family sizes should complete our present results.