Finns det ett samband mellan födelsedatum och prestation vid avelsbedömning av Islandshästar?

Abstract: The brood mare’s estrus season start in February and continues to September. It results in foal being born between Mars and September, which makes the age difference up to six months in the same calendar year. In previous studies of horses in disciplines like flat race, trotting, show jumping and dressage it has been shown that horses being born early in the year perform better than horses born late. How this affect the performance of the Icelandic horse has not been studied before. The aim of the study was to investigate if there is any relationship between birth date and performance at breeding field test Results can give breeders information about birth date affecting performance. The questions were if the Icelandic horse's performance in breed evaluation test is affected by birth date and does early born horses perform better than late born? The hypothesis that were tested in the study is that early-born horses perform better during breeding field tests at the age of four and five years. Data from four and five-year-old horses assessed for both conformation and rideability traits with registered birthdate, born between 2000-2013 was retrieved from the web-based stud-book of Icelandic horses. They were placed in three different groups after birth month and categorized after the results for conformation, rideability and total score. The result showed that birth-month did not affect the results of total-, conformation or rideability score. The breed evaluation test score for conformation in June-July was significantly higher than conformation score in August-September (p <0,0031). Gender and place for assessment had a high significance (p <0,0001). The conclusion was that performance at breed evaluation tests is not affected by birth date. Performance seems to be affected more by genetic and other environmental factors. The DMRT3 gene and growing ratio could be two of these factors. Key words: age, breeding assessment, rideability, conformation