Précision de l'estimation de l'âge des chevaux par l'examen des dents: résultats d'une étude sur des juments de Trait belge

The aim of this study was to assess the accuracy of judging age from teeth, with standard aging guides, of mares from 2 to 20 years old registered in the Belgian draft horse stud-book. The replacement of the deciduous incisors by permanent teeth occurred when expected as the disappearance of the infundibulum on the permanent lower intermediate incisors. The disappearance of the infundibulum was however observed until 16 months earlier than expected on the central incisors and until 18 months later on the corner incisors with 64 % and 50 % of the concerned mares respectively. The modifications of the shape of the occlusal tables from oval to round occurred from 1 to 4 years earlier than expected. The risk to attribute an older age than the true age during the so called round period is lower when taking into account the disappearance of the cup cement leaving only an enamel spot on the occlusal table surface. The modifications of the shape of the incisor tables from round to triangular and to biangular was also observed earlier than expected but only with the central and intermediate incisors, not with the corner incisors. The measurement on photographs of the profile angle of the corner incisors confirmed that this angle decreases with age from about 134 degrees at about 5 years to about 72 degrees at 20 years. Statistical analyses of the differences between real ages and those estimated on pictures by a college of three experts, show that ageing horses from their dentition is more accurate for animals of 8 years old or less, than for older ones. For those animals, the overestimation was about 10 % of the real age.