Abstract
Genetic analysis of disorder incidence in farmed animals is challenged by two factors. Disorders in different cohorts and environments could be caused by different factors, leading to changes in heritability and to less than unity genetic correlations across cohorts. Moreover, due to computational limitations, liability scale heritabilities at very low incidence may differ from those estimated at higher incidence. We tested whether these two dilemmas occur in skeletal deformations of farmed salmonids using multigeneration data from the Finnish rainbow trout breeding programme and previous salmonid studies. The results showed that heritability was close to zero in cohorts in which management practices maintained incidence at a low level. When there was a management failure and incidence was unusually high, heritability was elevated. This may be due to computational limitations at very low incidence and/or because deformations are induced by different factors in different cohorts. Most genetic correlations between deformations recorded in different generations were weakly to strongly positive. However, also negative correlations between generations were present, showing that high liability at one time can be genetically connected to low liability at another time. The results emphasise that genetic architecture of binary traits can be influenced by trait expression.
Highlights
IntroductionTo ensure profitable and ethical farm animal production and domestication, animal welfare must be addressed
Improved farmed animal welfare is a fundamental issue for present-day consumers
The occurrence of developmental disorders in farm animals should be controlled by means of improved management practices, and/or by selective breeding when traits have genetic variation
Summary
To ensure profitable and ethical farm animal production and domestication, animal welfare must be addressed. Developmental disorders, such as abnormal development of skeletal structures, occur among both wild and farm animals, but the phenomenon is exaggerated among farmed animals. This is due to at least three reasons. Selective breeding for high production may have detrimental effects on health traits [26, 31]. The occurrence of developmental disorders in farm animals should be controlled by means of improved management practices, and/or by selective breeding when traits have genetic variation
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