Monday, September 20, 2021

Thoracic asymmetry in ridden horses

 Muscle asymmetry in the thoracic region has implications for saddle fitting. If the muscle on one side of the withers is more developed than the other, this will affect saddle fit, potentially causing pain and discomfort. 

A study, led by assistant professor Dr. Katrina Merkies, at the University of Guelph, Ontario, Canada looked at muscular symmetry at the withers. 


Undergraduate students in the Department of Animal Biosciences, Julia Alebrand, Bethany Harwood,  Katharine Labarge and Laura Scott conducted a retrospective study of  490 horses. They studied withers measurements, taken with a flexible withers tracing tool, that had been recorded by a saddle fitting company.


Horses of various breeds (from Arabs and Thoroughbreds to stocky Warmbloods and Drafts) and a range of disciplines (dressage, hunter/jumper, recreational pursuits) were included in the study.


They found that almost 60% of horses had more muscle on the left side. 


In this population of horses, wither measurements were not significantly affected by horse breed, age, sex, height or level of training. Rider age, gender, height, weight and level of training did not affect wither measurements either.


The work is reported in Comparative Exercise Physiology. The authors report that horses in their study were asymmetric in their thoracic structure with most being larger on their left side than the right. They suggest that this asymmetry may be due to genetics, environment, or training. Importantly, it should be considered when fitting a saddle to the horse.


For more details see:


Investigation into thoracic asymmetry in ridden horses

K. Merkies; J. Alebrand; B. Harwood; K. LaBarge; L. Scott.

Comparative Exercise Physiology (2020), Vol 16, 1, pp. 55-62(8)


To find out more about the study, watch a video interview with Dr. Merkies

Sunday, September 19, 2021

Infectious disease surveillance service

The Horserace Betting Levy Board (HBLB) has announced steps towards re-establishing on a long-term basis the essential equine infectious disease surveillance provision that had been performed by the Animal Health Trust (AHT) until its closure in July 2020.

Acting on the recommendations of an industry-wide committee set up to assess options for the future, HBLB has concluded an agreement from August 2021 with Rossdales Ltd to provide the diagnostic microbiology testing capacity, in conjunction with the epidemiological surveillance and monitoring unit that will now be based at the University of Cambridge Veterinary School.

The former AHT team, headed by Dr Richard Newton, will be employed by Cambridge University under the new agreement and will continue to respond to disease outbreak incidents and to produce daily updates on infectious disease reports worldwide for the benefit of the health of all horses, Thoroughbred and non-Thoroughbred.  

Dr Alastair Foote, director of Rossdales Laboratories, added: “We are delighted to have been awarded the tender, and to be able to provide continuity of the former AHT services that were critical to the equine industry, maintaining essential diagnostic testing and surveillance work.  Our recent major investment in new laboratory facilities at our Newmarket site has meant we have been able to rapidly accommodate the required testing requirements, with new tissue culture and virus isolation facilities, and we look forward to working alongside the surveillance and research team at Cambridge.”

For more details, see:

Thursday, August 26, 2021

Measuring eye temperature with thermography

The measurement of eye temperature by Infra-red thermography (IRT) is affected by endogenous and environmental factors and does not relate to rectal temperature, a recent study has found. 

The maximal eye temperature (MaxET) measured with IRT has been extensively used in equine research. It is a popular technique as it is non-invasive and does not require direct contact with the individual.


A study, by Anna Jannson and colleagues, published in the journal Physiology and Behavior, investigated factors influencing eye temperature in horses when measured using infra- red thermography (IRT) under field conditions.


The research team took 791 maximal eye temperatures (MaxET) measurements from 32 horses in Sweden in five different months and on five farms over a 12 month period.


They found that in horses observed at rest in their home environment, MaxET is affected by endogenous (sex and breed) and environmental factors (farm, location, and month of the year). MaxET shows no relationship to rectal temperature.


The authors point out that these findings have relevance in both clinical and research settings. 


“This indicates that eye temperature does not appear to be a sensitive method to monitor for example fever, where rectal temperature is traditionally used.”


They add “endogenous (sex and breed) and environmental variation between months were major factors influencing eye temperature and should be considered in the modelling and design of future field experiments.”




For more details, see:


An investigation into factors influencing basal eye temperature in the domestic horse (Equus caballus) when measured using infrared thermography in field conditions

Anna Jansson, Gabriella Lindgren , Brandon D Velie , Marina SolĂ©.

Physiol Behav (2021);228:113218

 doi: 10.1016/j.physbeh.2020.113218

Photo by Anna Jannson et al (CC by 4.0)

Wednesday, August 25, 2021

Feral equids dig wells that benefit others

Research shows that wells dug by feral donkeys and horses benefit other species and the environment.


Erik Lundgren and others studied the behaviour of feral equids in the Sonoran desert in the south-western United States. A report of the work has been published in the journal Science.


They found that feral horses and donkeys dig their own wells, which are sometimes up to two metres deep. The wells provide benefits for other species and lead to an increase in biodiversity in the surrounding area.

As part of their research,  Erick Lundgren and his colleagues monitored four separate streams in part of the Sonoran desert in Arizona, using camera traps to observe the activity around the wells.

Feral donkey (left and horse digging for water. Photo (c) Erick Lundgren 

The streams usually fill with groundwater but dry up in the summer. The research team surveyed each stream every few weeks over three summers and found that horses and donkeys in the area dig wells there to access the groundwater. 


“It’s a very hot, dry desert and you’ll get these pretty magical spots where suddenly there is surface water,” said Lundgren.

"The donkey wells kept water in the system. And these features were used by pretty much every species you could picture, including some surprising ones like black bears, that we didn't expect to see in the desert." 


Apart from the donkeys and horses, the team saw 59 other vertebrate species at the wells, 57 of which were recorded drinking from the wells. 

Other species that they caught on camera visiting the wells included mule deer, bobcats, Woodhouse's scrub jay and javelinas.

The team even spotted some river tree species sprouting from abandoned wells, indicating they also serve a role as plant nurseries.

The researchers also found some riparian tree species (ie those that grow alongside water courses) sprouting from abandoned wells, indicating a wider environmental benefit.

For more details, see: 

Equids engineer desert water availability

Erick J. Lundgren, Daniel Ramp, Juliet C. Stromberg, Jianguo Wu, Nathan C. Nieto (deceased), Martin Sluk, Karla T. Moeller, Arian D. Wallach

Science  (2021) Vol 372, Issue 6541, pp. 491-495

DOI: 10.1126/science.abd6775