Carpal and fetlock conformation of the juvenile Thoroughbred from birth to yearling auction age.

The research investigates how the forelimb conformation, specifically the carpus (wrist) and fetlock (ankle) , of young Thoroughbred horses changes from birth to yearling sale age. Additionally, it explores which factors could influence these changes such as birth weight, sire’s conformation, and age.

Study Methodology

• The study utilized a sample size of 119 Thoroughbred foals. The carpal and fetlock conformations of these foals were subjectively assessed within the first month of their lives and then subsequently at 30-day intervals until they reached at least 120 days old. Around 70 subjects were examined further at 60-day intervals until their second year.
• The study categorized the conformation grades into five age groups, which were the first 7 days, and at an average of 46, 176, 362 and 525 days.
• The conformation of the sire and dam for each foal was also evaluated and compared to the foal’s conformation.

Research Findings

• All the foals in the study demonstrated deviations in their carpal conformation such as valgus (an outward deviation of a limb), outward rotation and offset. About 30% of the foals also showed deviations in their fetlock conformation.
• The study found a link between heavier birth weights and specific conformation deviations – carpal offset and inward fetlock conformation. Heavier yearlings were also more likely to display carpal valgus conformation.
• The sire’s carpal conformation (offset and outward rotation) was found to correlate with a similar conformation in the yearling.
• The research also found changes in the foals’ conformation over time. The carpal conformation became less valgus and more offset during the study period, while the fetlock conformation showed an increase in inward deviation in the first six months of the study.

Conclusions

• The researchers observed significant changes in the carpal and fetlock conformation in young Thoroughbred horses from birth up to 18 months.
• The sire’s phenotype or physical traits can have an influence on the foal’s carpal conformation during the yearling stage.
• Weight, specifically at birth and at yearling stage, is also associated with the carpal and fetlock conformation of the yearling.
• New factors associated with forelimb conformation deviations have been identified, which can provide breeders with valuable insights for managing young racing stock.