Age-Related Differences in Short-Term Transportation Stress Responses of Horses.

The study investigates the differences in stress responses between young and aged horses during short-term transportation. The results suggest that while cortisol levels – a key biomarker for stress – do not differ significantly between the two groups during transport, aged horses do exhibit a greater increase in insulin post-transportation.

Study Design and Participants

• The study was conducted on eleven mares, divided into two groups based on their age – one group consisted of five aged horses (22 ± 1 year) and the other group six young horses (2 ± 1 year).
• The horses were transported for a duration of 1 hour and 20 minutes. Samples of peripheral blood and saliva were collected at several time points before and after transportation.

Data Collection

• Specific time points for collection were 2 to 3 weeks before transportation (baseline), 24 hours before transportation, 1 hour before loading, 15 minutes after transportation, 30 minutes after transportation, 1 to 3 hours post-transportation, 24 hours post-transportation and 8 days post-transportation.
• Heart rates, rectal temperatures, under the tail temperatures, serum cortisol, plasma ACTH, serum insulin, salivary cortisol and salivary IL-6 were assessed.
• A process known as qPCR was used to measure gene expression of the cytokines IL-1b, IL-2, IL-6, IL-10, IFNγ, and TNFα in whole blood samples.
• The level of IFNγ and TNFα production was also determined using isolated, stimulated and stained peripheral blood mononuclear cells.

Results and Findings

• The findings showed that stress indicators such as serum and salivary cortisol levels, as well as heart rate, increased during transportation in all horses regardless of age.
• Rectal and under the tail temperatures were observed to increase more in young horses compared to aged ones.
• The level of plasma ACTH, a hormone related to stress was higher in aged horses and increased after transportation.
• A remarkable finding was that insulin levels increased more in aged horses post-transportation. Since insulin regulates blood glucose levels, this could be an important factor for stress regulation in older horses.

Conclusion

• From the study, it can be concluded that while age doesn’t majorly influence cortisol responses to short-term stress from transportation, it does have an effect on the insulin response in aged horses post-transportation.
• This suggests that older horses may respond differently to stress and that age needs to be taken into consideration when managing horse transportation.