Fitness Traits in Animal Breeding Programs

Traits measuring reproduction and survival sometimes show a negative genetic trend in livestock populations despite their importance to profitability. This occurs due to inbreeding depression and selection for other traits. For many traits there are genes with an allele that increases the trait value but is initially at low frequency due to negative effects on fitness. Therefore, theory suggests that fitness traits will tend to decline due to selection for other traits even if this is not predicted by the genetic correlation in the base population. The most important recommendation to overcome this problem is simply to include fitness traits in the breeding objective, the recording scheme and the selection index. The economic weight given to fitness traits should take account of the high likelihood that they will be important in the future whereas other breeding objectives are more likely to change with time.