Retrospective analysis of post-mortem findings in Thoroughbreds aged from birth to 18 months presented to a UK pathology laboratory.

The researchers conducted a study to establish causes of death in young Thoroughbred horses before they start race training, by analyzing post-mortem reports from a UK pathology lab. The findings highlighted congenital defects and pneumonia as key health issues in this horse group, with factors like age significantly impacting specific health problems.

Methodology

• The study analyzed post-mortem examination reports of Thoroughbreds aged from birth to 18 months from a pathology laboratory in Newmarket, UK, spanning January 2006 to December 2020. Here, reported pathologies were categorized to understand the leading causes of mortality in young Thoroughbreds.
• The research also looked at comorbidities and identified pathogens, if available, in the reports. This helped in understanding any associated diseases or harmful organisms that might have contributed to the death of these horses.
• The researchers then assessed the associations between age and specific pathologies using logistic regression analysis. This statistical method is useful for predicting the likelihood of occurrence of an event by fitting data to a logistic curve. It provided an understanding of if and how age affects the incidence of different pathologies.

Findings

• From the 144 eligible Thoroughbreds presented for post-mortem examination, 137 had an available report and pathologist’s diagnosis. Among these, congenital defects were found to be the most common (20%), with developmental orthopedic disease (DOD) being the primary issue, noticed in 69% of cases with congenital defects.
• Pneumonia was identified as a significant problem, particularly during the pre-weaning period, with the bacterium Rhodococcus equi identified in 50% of pneumonia cases.
• The researchers found a strong correlation between age and specific pathologies. Congenital defects were significantly more common in horses aged 0-2 days compared to those between 4 and 18 months. In contrast, pneumonia had significantly higher odds in horses aged 1-4 months than in those aged 0-2 days.

Conclusion

• The study concluded that the manifestations of DOD as conformational deformities are a significant contributor to perinatal mortality (death within the first few weeks after birth) and that distinct pathologies vary with age in young Thoroughbreds.
• Such findings could help breeders and veterinarians to improve care for young horses, with an enhanced focus on early detection and prevention of these common diseases and conditions.