Hanne Fjerdingby Olsen defended her thesis on June 17th 2011

Ane Gro Siri Skjelfjord

Genetic variation and management of the Norwegian horse breeds

Summary from the thesis - PhD thesis 2011:05

The Norwegian horse breeds suffer from strong competition in the market from imported, specialized breeds. Decreasing population sizes, especially for the Fjord, the Døle and the Nordland/Lyngen, and risk of rapid accumulation of inbreeding is a challenge. This challenge address the need for maintaining these breeds through knowledge of the build-up of relationships in the populations and long-term breeding plans, including breeding goals ensuring the future demand for the breed and proper selection tools which maintain the genetic variation.

The first study examined the genetic variation in the Døle and in the Nordland/Lyngen, through investigation of the pedigree structures, revealing a quite different retrospective picture in these two breeds, due to amongst others periods of imports (trotters and North-Swedish) in the Døle and indications of maximum avoidance of inbreeding in the Nordland/Lyngen. Both populations are considered to have challenges in handling the buildup of relationship, and are recommended to base future management on optimal contribution selection.

The second study was a simulation of the small, Norwegian horse populations to examine the effect of various actions on the effective population size. The main results showed that each of the breeds should be managed with at least 200 foals born and registered per year with a large fraction of the offspring from young sires, to ensure that more sires are being used. In these populations omission of selection was of minor importance for the effective population size.

In the third study different alternatives for genetic evaluation of racing performance in the North-Swedish and the Norwegian trotter was validated based on cross-validation of standardized earnings. The current bivariate linear approach, including racing status and earnings as traits, was compared with a threshold-linear model and the univariate alternative with earnings only. Racing status appeared to be highly influenced by ancestry, which resulted in a high heritability, a high genetic correlation with earnings and likely, an inflated genetic trend of earnings. However, due to earnings being predicted more accurately and the inability to discriminate between models for genetic trend, the current approach is still recommended for practise.

The fourth study describes the application of optimal contribution selection (OCS), by use of Gencont with overlapping generations, in the Norwegian and the North-Swedish cold-blooded trotter. The study showed that OCS can be used as a dynamic tool for selection in the Norwegian breeds to ensure recruitment of young stallions as well as culling of older stallions with already large genetic contributions to the population.

Updated: 12.09.11
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