Genet. Sel. Evol.
Volume 39, Number 5, September-October 2007
|Page(s)||529 - 543|
|Published online||27 September 2007|
Changes in the expression of genetic characteristics across cohorts in skeletal deformations of farmed salmonidsAntti Kausea, Ossi Ritolab and Tuija Paananenb
a MTT Agrifood Research Finland, Biotechnology and Food Research, Biometrical Genetics, 31600 Jokioinen, Finland
b Finnish Game and Fisheries Research Institute, Tervo Fisheries Research and Aquaculture, 72210 Tervo, Finland
(Received 2 November 2006; accepted 24 April 2007; published online 27 September 2007)
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.
Key words: animal breeding / animal health / deformation / heritability / salmonids
Correspondence and reprints: Antti.Kause@mtt.fi
© INRA, EDP Sciences 2007