Osteoarthritis (OA) is a prevalent condition in horses, leading to changes in trabecular bone structure and radiographic texture. Although fractal dimension (FD) and lacunarity have been applied to quantify these changes in humans, their application in horses remains nascent. This study evaluated the use of FD, bone area fraction (BA/TA), and lacunarity in quantifying trabecular bone differences in the proximal phalanx (P1) in 50 radiographic examinations of equine metacarpophalangeal joints with varying OA degrees. In the dorsopalmar view, regions of interest were defined in the trabecular bone of the proximal epiphysis, medial and lateral to the sagittal groove of P1. Lower BA/TA values were observed medially in horses with severe OA (P=0.003). No significant differences in FD and lacunarity were found across OA degrees (P>0.1). FD, BA/TA, and lacunarity were not effective in identifying radiographic texture changes in the P1 trabecular bone in horses with different metacarpophalangeal OA degrees.

Plasma or serum amino acids are used to evaluate nutritional status and metabolic disorders. In this study, we aimed to set reference values of serum amino acid concentrations in the Noma horse, a Japanese native horse. Thirty-one horses were classified into six age groups: neonatal foal (0–4 days), foal (0.5–1 years), youth (5 years), middle age (10 years), old (15 years), and extra-old (>20 years). Horses >5 years of age were analyzed together as the adult group. In the adult horses, there were no significant differences among the serum amino acid concentrations of each age group. The foal group had higher concentrations of alanine, aspartic acid, glutamic acid, α-aminoadipic acid, and 3-methyl-histidine than the adult group. The neonatal foal group had higher serum concentrations of phenylalanine, lysine, alanine, proline, aspartic acid, glutamic acid, β-alanine, and β-amino-iso-butyric acid and lower tryptophan concentrations and Fischer’s ratios than the adult group. The neonatal foal group had higher β-amino-iso-butyric acid concentrations and lower tryptophan and 3-methyl-histidine concentrations than the foal group. Therefore, reference values might be set separately in neonatal foals, foals, and adult horses. The data for the serum amino acid concentrations can be used for health care through physiological and pathological evaluations in Noma horses.