Saturday, October 26, 2019

Prebiotics: help or harm?

Prebiotics may do more harm than good according to a recent study in Germany.

Prebiotics are often added to horse feed in order to stabilise the horse’s intestinal flora and promote good digestive health. They are indigestible fibres that can stimulate the growth and activity of certain beneficial bacteria in the large intestine. 

However, researchers at Martin Luther University Halle-Wittenberg (MLU) and the University of Veterinary Medicine Hannover (TiHo) found that prebiotics only have a limited stabilising effect on the intestinal flora of horses. Before they can reach the intestines, commercially available supplements partially break down in the animals' stomachs, which can lead to inflammation of the stomach lining.

The team therefore suggests preparing prebiotic food supplements so that they don't take effect until they reach the large intestine. The study appeared recently in the journal "PLOS ONE".

"Horses have a relatively small, non-diverse core microbiome and are therefore very susceptible to digestive disorders," explains Professor Annette Zeyner, head of the animal nutrition group at MLU. However, according to the scientist, insufficient research has been conducted on whether the use of prebiotics actually does produce the desired effects. Her research group explored this question in partnership with Professor Gerhard Breves’ lab from TiHo.

For the study, the team investigated the effect of feeding Jerusalem artichoke meal (JAM) to horses. Jerusalem artichoke is often used as a prebiotic for horses and contains high amounts of certain carbohydrates; fructo-oligosaccharides and inulin.

In addition to their normal feed, six animals received JAM. Another six horses received a placebo with their normal feed. The researchers then analysed the balance of bacteria in the digestive tract of the animals of both groups. 

They found that the prebiotics were already being fermented in the stomach by the microorganisms naturally living there - i.e. they were taking effect much too early. "The fermentation process leads to the formation of organic acids that - unlike in the large intestine - can damage the mucous membrane of the horse’s stomach," says Maren Glatter, a member of Zeyner’s group and lead author of the study.

However, the bacterial diversity of the entire digestive tract did increase, which probably also produces the desired protective effect. "Still, the prebiotics are probably more harmful than beneficial when used in their present form," Zeyner surmises. Instead, the substances must be treated so that they arrive in the large intestine in one dose in order to have a positive effect on the intestinal bacteria living there without stimulating overactivity.

For more details, see: 

Modification of the equine gastrointestinal microbiota by Jerusalem artichoke meal supplementation.
Glatter M, Borewicz K, van den Bogert B, Wensch-Dorendorf M, Bochnia M, Greef JM, Bachmann, H. Smidt, G. Breves, A. Zeyner.
PLoS ONE (2019) 14(8): e0220553.

Response of horses to increased rider’s weight

Previous studies have found that physiological responses and gait symmetry parameters are adversely affected when horses carry heavy riders, for example when the rider:horse weight ratio increases from 20 – 35%.

New research should help shed more light on how increased rider weight may affect a horse during exercise under saddle, looking at lower rider:horse weight ratios which are more typical  for warmblood horses. 

Janne Winther Christensen, from Aarhus University in Denmark, and her research team looked at the
impacts of a sudden increase in rider weight on horse behaviour, physiological responses, and gait symmetry. The initial results of this study were presented on August 19, 2019, at the 15th annual International Society for Equitation Science (ISES) conference held at the University of Guelph.

Christensen explained, “The effect of rider weight on horse welfare is much debated and is likely affected by a number of factors including horse type, work intensity, horse training level, and rider skills.”

The study included 20 rider-horse combinations, and the researchers asked riders to complete a standard dressage test in a balanced cross-over study. The riders rode with no additional weight, or with an extra 15% or 25% of their body weight added to a vest. The horses’ heart rate, salivary cortisol, gait symmetry and behaviours (e.g. head tossing, tail swishing, mouth opening) were measured during the test.  

The researchers found that the increased rider weights did not significantly affect the heart rate, salivary cortisol, behaviour and gait symmetry of horses. It should be noted that the maximum rider: horse weight ratios fell between 15 – 23% and the exercise intensity was relatively low. Christensen says, “Thus, within this weight ratio range and during light to moderate exercise, acute increases in rider weight did not induce changes in the parameters analysed so far.”

The study also compared rider symmetry measured on the ground with their symmetry on horseback when riding with and without additional weight. On ground symmetry was measured as weight on left and right leg respectively, while standing on two identical bathroom scales. In addition, their mobility and balance when sitting on a gymnastic ball was scored based on their ability to perform standardized exercises. Poor mobility on the gymnastic ball was associated with weight asymmetry, i.e. the poorer the mobility the larger the weight asymmetry. Rider crookedness in the saddle was measured using a saddle pressure mat.

Almost all riders (19/20) had more weight on the right side of the saddle. Crookedness correlated significantly with weight asymmetry on the ground, but only in the 0% weight treatment, and not when the riders rode with an additional 15 and 25% weight, suggesting that artificial addition of weight might make some riders less crooked as they become more aware of their relative asymmetry.
Thus, a simple weight symmetry test with two ordinary bathroom scale weights reflects rider crookedness in the saddle and can help riders become aware of their imbalance. Lack of mobility of the pelvis on a gymnastic ball also reflects this imbalance.

Kate Fenner, ISES council member, was enthusiastic that Christensen attended this year’s conference to share the results. Fenner says “We know that there is a great deal of interest in the potential effects of rider weight on equine welfare. We’re happy that we are able to provide a meeting area for researchers to share new findings like these each year, and hopefully spark more collaborations and research in these areas.”

For more details, see:

Did you put on weight? The influence of increased rider weight on horse behavioural and physiological parameters 
J.W. Christensen, M. Uldahl
Proc 15th ISES Conference, (2019) p33

On-ground rider weight symmetry mirrors balance in the saddle M.
Uldahl, J.W. Christensen
Proc 15th ISES Conference, (2019) p34

You can download the Proceedings of the 15th International Society for Equitation Science Conference  at:

Evaluating English saddle fitting

© Nicole Ciscato | Dreamstime.comPoorly fitted saddles can adversely affect welfare and impair performance of ridden horses. The Saddle Research Trust Research Workshop, held in December 2018, identified a need for improved education of saddle fit evaluation among professional equine practitioners.

An educational article was subsequently commissioned by the editor of the peer-reviewed scientific journal, Equine Veterinary Education, that would simplify the complex subject of saddle fitting evaluation.

The article aims to provide practical guidance to equine veterinarians to assist in their decision-making process whilst carrying out routine assessments when a horse is evaluated ridden, such as for pre-purchase, lameness or poor performance examinations. It also clarifies when a saddle may be contributing to pain and performance problems and when the veterinarian should refer the client to a saddle-fitting professional.

“Evaluating the suitability of an English saddle for a horse and rider combination”, a collaboration between Anne Bondi, Sue Dyson, Sue Norton and Lawrence Pearman, is a comprehensive mini manual aimed at vets and physiotherapists and which will be equally of interest to other professional equine practitioners.

Thanks to the generosity of the publishers, the article is free to view. Go to: