Comparative study of dental age estimation methods against known chronological age in Nigerian local horses

Dental age estimation in horses is very important in the context of quality healthcare, breeding programs, and welfare management. However, information on the most suitable dental age estimation methods for Nigerian local horses is not available in the literature. We evaluated and compared dental age estimates based on six dental age estimation methods with known chronological ages of Nigerian local horses to establish the most accurate techniques for this population. A cross-sectional study of 180 Nigerian local horses was conducted in Ibadan, Nigeria. Six dental age estimation methods (eruption patterns, grinding surface, cups, dental stars, angle of incidence, and Galvayne's groove) were applied by three blinded veterinarians to independent groups of 30 horses each. Data analyses included t-tests, Pearson correlation coefficients, and Bland-Altman plots. None of the estimated ages based on the estimation methods showed significant differences from the chronological age (P>0.05). The angle of incidence method showed perfect alignment with chronological age (11.9 ± 5.4 years) and the highest correlation (r=0.988, P<0.001). The eruption pattern method showed the smallest variation in estimates (range of agreement: 2.3 years), while Galvayne's groove exhibited the largest variation (range of agreement: 9.9 years). Strong correlations were also observed for the grinding surface shape and dental stars assessments (both r=0.955, P<0.001). The angle of incidence method showed the highest correlation with chronological age for Nigerian local horses (between 5 and 30 years, r=0.988), though it provides age estimates in broad categories rather than precise years. The eruption pattern method demonstrated the highest precision for younger horses (between 3 and 5 years), with the smallest range of agreement (2.3 years). Veterinarians and horse owners in Nigeria should prioritize these methods for reliable age determination, while exercising caution when using Galvayne's groove method due to its higher variability.