Effects of fence height on total and free iodothyronine changes in horses after experimental show jumping sessions.

This research investigates how different heights of showjumping fences affect the thyroid function in horses, specifically the levels of total and free iodothyronines, a type of thyroid hormone. Findings indicate that higher fences induce a greater release of certain thyroid hormones, which may be linked to skeletal muscle and thyroid stimulation activity.

Research Methodology

• The study employed a randomised crossover study design which involved six trained horses.
• The experiment observed these horses over three different experimental showjumping sessions, with each session varying in fence height: 1.00m, 1.10m, and 1.20m respectively.
• Different aspects of the horses’ thyroid hormone levels were recorded at various intervals, specifically before warm-up, after warm-up, 5 and 30 minutes post-exercise.
• Indicators such as T(3), T(4), fT(3), and fT(4) concentrations were measured and analysed using Enzyme-Linked Immunosorbent Assay (ELISA) competition with streptavidin technology.
• Statistical methods, such as Repeated Measures Analysis of Variance (RM-ANOVA) and a post hoc multiple comparison test (Bonferroni), were applied to thoroughly assess the data.

Research Findings

• Basal T(4) values were recorded as changing over the different showjumping sessions, with significance of P < 0.05.
• Following warmup, T(4) concentration was lower than basal levels during the first session (significance of P<0.05).
• Higher than basal values were recorded 30 minutes post-exercise for T(3) (P < 0.001), T(4), and fT(4) (P < 0.01) in the second session, with T(4) (P < 0.05) and fT(4) (P < 0.01) elevated in the third session.
• The interaction between fence height and time had a significant impact on T(3) (P < 0.03) and fT(4) (P < 0.03) measurements.

Conclusions

• The activity of showjumping over the highest fences induced a release of the thyroid hormone T(3) from the horse’s skeletal muscle. This increase is likely due to an increase in 5′-desiodase activity.
• In the same high fence conditions, it was observed that an increase of fT(4) was also stimulated, potentially due to changes in the thyroid’s capacity to bind iodothyronines.