External and Radiographic Hoof Angles Differ in Thoroughbred Foals. (June 2014) - Curtis, S
Abstract : Introduction: Poor hoof angle and hoof pastern alignment has been linked to lameness in mature horses. External characteristics, such as the hoof pastern axis and hoof angle, are commonly used to assess dorsopalmar conformation in the same manner in foals. The hoof wall integument and distal phalanx is parallel in healthy mature horses but not in foals: this is not understood. Methods: The front feet of 22 Thoroughbred foals were radiographed and measured in June and again in November. Lateromedial radiographic images were measured (Osirix) for hoof integument angle and width, and proximal, middle and distal phalanx angles. The data were tabulated in Excel and analysed in Minitab. After assessment for normality (Anderson‐Darling), potential relationships were assessed for differences between June and November using paired t‐tests and regression analysis. Results: The dorsal hoof angle became more acute with age, R 2 = 0.3326, the mean of June, 59.05 ± 3.662°, was significantly different from November, 53.64 ± 2.7824°, P<0.0001. The hoof pastern axes were broken forward in June, 6.1 ± 2.1°, in November 2.5 ± 1.6°, whereas the phalangeal axes were broken back, June, ‐11.0 ± 7.5°, November, −8.3 ± 4.4°. There was a significant relationship between age and hoof pastern axis alignment, R 2 = 0.3746; P<0.0001. The phalangeal axis did not correlate with age. The relationship between age and parallelism of the integument was significant R 2 = 0.4867; P<0.0001. Conclusions: The cause of the non‐alignment of the hoof pastern axis and phalangeal axis in Thoroughbred foals is widening of hoof integument proximodistally and circumferential bone thickening of the distal phalanx. Assumptions of phalangeal angles based on external characteristics cannot be made in foals. Ethical Animal Research: Approval was given by the University of Central Lancashire Animal Projects Committee. Explicit owner informed consent for participation in this study is not stated.Sources of funding: World Horse Welfare partially funded this study.Competing interests: none.