The effect of nutritional products on equine stress response
Stress and anxiety in horses are a common problem and can be difficult facing everyday management tasks. Several nutritional products claim to reduce these stress responses in horses, despite the lack of scientific assessment of these products. The aim of this study was therefore to compare the effects of acepromazine (ACE), a magnesium-based formulation and a placebo paste in horses participating in tasks typical of normal equine management.
Six horses were selected for the study. All of the horses were known to show aversion to at least one of the five tasks; loading onto an equine weighbridge, loading onto a two-horse trailer, unaccompanied transport in a two-horse trailer, jugular venous blood sampling, and ten minutes in a stall with an unfamiliar object. Horses received a single dose of one of the nutritional products exactly thirty minutes before commencement of tasks. Horses were given ten minutes for task completion. Peak and average heart rate, time to completion of tasks and plasma cortisol were measured.
Results showed that the five tasks induced an increased peak and average heart rate and an increased plasma cortisol demonstrating a stress response. Acepromazine and the magnesium formulation significantly reduced the average heart rate when animals performed the first task. Neither the acepromazine, the magnesium formulation or the placebo showed a significant effect on any other task other than the first. None of the nutritional products had any significant effect on plasma cortisol levels or time taken to complete tasks.
The authors concluded that oral acepromazine and the magnesium formulation reduced average heart rate during a stressful task, and may therefore assist horses with performing these tasks thirty minutes after dosing. However, further studies on the effect of these treatments on plasma cortisol are required.
Do you use a magnesium-based antianxiety formulation?
If yes; have you ever noticed difference in behaviour in stressful situations?
If no; would you consider using it?
Expert opinion by Debby Gudden
This study concluded that oral acepromazine and the magnesium formulation reduced average heart rate during a stressful task, however the study was funded by a company that produces magnesium calming supplements. Even though the researchers stated that this did not affect the outcome in any way, it probably has caused a conflict of interest. Furthermore, it is also interesting that other than this study, there are currently no published scientific studies demonstrating a calming effect of magnesium supplements in horses. Magnesium supplementation can interfere with calcium balance and lead to an increased risk of orthopaedic problems, and should therefore be fed with caution. Extra magnesium can be fed when horses suffer a deficiency. However, magnesium deficiency in horses is rare and most diets contain adequate magnesium.
> From: Pearson et al., J Equine Vet Sci 51 (2017) 86-91. All rights reserved to Elsevier Inc.. Click here for the online summary.