GENETIC-PARAMETERS FOR LINEAR TYPE TRAITS IN SHETLAND PONIES

In this study heritability, phenotypic and genetic correlation were estimated between 28 type traits in the Dutch Shetland pony population. Data consisted of linear records on 358 males and 2337 female ponies classified in 1989 and 1990. Genetic parameters were estimated from a sire model using REML algorithms. Heritability estimates for scored traits ranged from 0.07 to 0.39. Traits which characterize movement had relatively high heritabilities while low heritabilities were found for most leg traits. Traits scored on withers and shoulders were highly correlated genetically. Leg traits generally showed moderate genetic correlations. Genetic correlations between movement traits are high. It is concluded that the data collected on type traits can be used to estimate breeding values for stallions. To enable a good comparison of breeding values of stallions over regions the difference in standard deviation between classifiers needs to be corrected for. Effective selection for 28 correlated traits is likely to be ineffective. Alternatives are discussed to summarize the information into a smaller number of traits to enable an effective breeding strategy.