Heart irregularities in Thoroughbred racehorses.

 

Atrial fibrillation is the most commonly recognized disturbance of heart rhythm in athletic horses. It is an important cause of poor performance, and has implications for safety of horse and rider.

In atrial fibrillation (AF) the heart beats with a haphazard, “irregularly irregular” rhythm. The condition may be termed “paroxysmal” (when it recovers spontaneously within 72hrs) or “persistent” (which continues if not treated). 

 

Laura Nash and colleagues studied records of horses racing in Hong Kong over a ten-year period up to July 2017. They looked at the incidence of AF in poorly performing horses, and whether having had a previous episode of AF increased the likelihood of a horse being affected.

 

The full, open access, report of their study is published in the Journal of Veterinary Internal Medicine.

 

They report that, from a total of 96,135 race starts, atrial fibrillation was identified in 4.9% of horses, with an overall incidence of 2.7 episodes per 1000 starts. Many horses were retired after the first episode of AF.

 

Having had a previous episode of AF increased the risk of AF, and recurrence was more likely in horses that had been treated previously for persistent AF, than in horses that had previously had paroxysmal AF.

 

The researchers comment: “We identified a high rate of recurrence in Thoroughbred racehorses after both paroxysmal and persistent episodes of AF. This substantial AF burden could arise from underlying microstructural myocardial lesions and electrical remodelling.”

 

They concluded that, “although horses can have long and successful careers after AF, the arrhythmia should not be considered benign, and the suitability of horses to continue their racing careers should be assessed on an individual basis.”

 

For more details, see:

 

Incidence, recurrence, and outcome of postrace atrial fibrillation in Thoroughbred horses

Laura C Nath, Adrian D Elliott, Joe Weir, Peter Curl, Sarah M Rosanowski, Samantha Franklin.

J Vet Intern Med (2021) 35(2): 1111–1120. 

https://doi.org/10.1111/jvim.16063

Monitoring signs of laminitis

A new scoring method has been shown to be useful for monitoring the progress of cases of endocrinopathic-laminitis. Endocrinopathic-laminitis or hyperinsulinaemia-associated laminitis (HAL) is a common form of the condition, typically encountered in overweight animals.
Being able to grade the severity of the signs is useful, both for assessing the response to treatment in clinical situations, but also for assessing potential new treatments when they become available.
 
The 4-point Obel scale has been used for many years to describe the severity of laminitic signs. (See below). It was devised for use with severe cases caused by sepsis or starch overload, and may not be as well suited to cases of HAL, which often show a more gradual onset. 
 

A new method was developed by Meier and colleagues (See below), which examines five key clinical signs: weight shifting, response to lifting a foot, gait at the walk and turning in a circle, and palpation of the digital pulse.

 

The value of this new method was investigated in a randomised controlled field study involving eighty horses and ponies with naturally occurring HAL, seen at 16 veterinary practices in Germany.

Independent veterinarians assessed the severity of laminitis using both the traditional Obel method and the Meier method. Assessments were made on the day of diagnosis then 4, 9, 14, 25 and 42 days later. Pain medications were withheld for 24 h before clinical examination in all cases.

 

The researchers found that the time taken for the laminitis to improve varied between individuals, and was difficult to monitor accurately using the Obel method. The Meier method could identify more subtle changes. They noted that there was considerable variation in the rate of improvement of individual clinical signs. For example, lameness when turning in a circle persisted longer than signs of weight shifting and reluctance to allow the front leg to be lifted.

 

A full, open access, report of the work is published in the journal BMC Veterinary Research. The authors conclude that the Meier method provides a reliable and consistent method for monitoring the clinical status of horses with HAL.

 

They suggest that the pattern of improvement described in their study should provide a useful benchmark against which individual cases and new treatments can be assessed.

 

 

Table 1 The Obel method of laminitis diagnosis and severity grading (Obel, 1948)

Laminitis grade	Grade description
Normal	Horse appears sound
Obel grade 1	At rest, the horse shifts its weight between the forelimbs; the horse is sound at the walk, but the gait is stilted at the trot in a straight line and on turning
Obel grade 2	The gait is stilted at the walk and the horse turns with great difficulty, but one forelimb can be lifted
Obel grade 3	The horse is reluctant to walk and one forelimb can only be lifted with great difficulty
Obel grade 4	The horse will only move if forced to

 

 Table 2 The ‘modified Obel’ or ‘Meier’ method of laminitis diagnosis and severity scoring

Order of examination	Criteria	Description	Points	Given Points
Stage 1
Examine horse standing	Weight shifting	No weight shifting	0
		Weight shifting – including shifting weight between all feet;	2
		Abnormal time spent lying down; placing forelimbs in front of body
Gently lift each foot up and put back down straight away	Forelimb lift	Prompt and willingly maintained (each forelimb)	0
		Reluctant and maintained with difficulty (each forelimb)	1
		Unable to lift foot/resists attempts to lift foot (each forelimb)	2
Stage 2
Conduct on hard surface Walk horse approx. 30 m side-on to examiner	Gait at walk	Normal gait	0
		Mild - short, stilted gait - still moves willingly	1
		Moderate - short, stilted gait - reluctant/difficult to walk	2
		Severe difficulty walking or unable to walk*	6
		*do not force horse to walk; skip gait at circle and continue with digital pulse
Turn on a short lead clockwise and anti-clockwise	Gait at circle	Normal circling	0
		Mild head rise, difficulty when turning, still moves willingly	1
		Moderate, sharp head rise, reluctance/difficulty turning	2
		Severe difficulty turning, slow and clearly painful	3
Stage 3
All feet must be square on ground	Forelimb digital pulse	Normal - able to palpate, normal magnitude but not bounding	0
		Increased magnitude or bounding digital pulse (each forelimb)	2
			Total Score

 

 Both tables from: The application of a new laminitis scoring method to model the rate and pattern of improvement from equine endocrinopathic laminitis in a clinical setting ( http://creativecommons.org/licenses/by/4.0/)

For more details, see:

 

The application of a new laminitis scoring method to model the rate and pattern of improvement from equine endocrinopathic laminitis in a clinical setting. 

Meier, A., McGree, J., Klee, R. et al. (2021)

BMC Vet Res 17, 16 

https://doi.org/10.1186/s12917-020-02715-7

"RoboGut" to study horse's gut microbiome

 

There is increasing interest in the gut microbiome, the mixture of bacteria and microorganisms living in the horse’s gut, and its relationship to health and disease.

Horses rely on microbes in the hind-gut to ferment the roughage in their diet, and break it down into nutrients they can absorb.

 

Disruption of the normal balance, for example by the overgrowth of a particular population of bacteria, may affect the normal healthy functioning of the horse’s gastrointestinal tract, and may result in disease.

 

Changes in the microbiome may lead to diseases affecting the gastro-intestinal tract – such as colic or colitis – and even conditions with more wide-reaching effects such as laminitis.

Researchers at Ontario Veterinary College (OVC), University of Guelph have developed a mechanical replica of the equine digestive system, known as “RoboGut”, which will to help them to understand the composition of a healthy horse’s gut microbiome.

 

Dr. Luis Arroyo, professor in the Department of Clinical Studies at the OVC, uses the horse robo-gut to understand how various food compounds are digested.

 

“The robo-gut offers us ways to understand mechanism of disease and potential treatment options for our patients, as well as helping us learn more about early detection and prevention of GI diseases,” says Arroyo. 

 

The researchers can alter the humidity and temperature to simulate the environment within the horse’s gut. 

 

“Through this manipulation, we can encourage a horse gut microbiome to thrive in the robo-gut,” says Arroyo. "Native microbiota play an important role in the digestion, absorption and fermentation of nutrients to maintain a healthy state."

 

“A healthy gut microbiome is essential for the proper systemic functioning of the horse’s entire body,” says Arroyo. “By looking at horse health holistically, we are able to prevent local and systemic ailments from flourishing.”

 

For more details, see:

 

https://ovc.uoguelph.ca/news/equine-robo-gut-helps-ovc-researchers-study-gastrointestinal-diseases-horses

Free Equine Webinar Series: Taking Science to the Stable

A free equine webinar series from the University of Guelph will run every two weeks until August 18. 

The talks aim to provide informative and insightful knowledge from experienced industry professionals.

Topics include:

 

• What’s Next? How to restart your business after a shutdown – Panel Presentation, June 30 at 7 p.m. EST 
• Foal Management and Nutrition of Newborn, Suckling, Growing and Orphan Foals – Don Kapper, July 14 at 7 p.m. EST  
• Routine equine handling using low stress and cooperative care techniques – Dr. Robin Foster , July 28 at 7 p.m. EST 
• Performance Nutrition – Feeding and Management of the Performance Horse – Don Kapper, August 4 at 7 p.m. EST 
• Turning Science into Stories for Horse Owners – Emily Esterson, August 18 at 7 p.m. EST

Registration is free but closes at noon the day before the event to ensure participants receive the Zoom link for the webinar on time. 

 

For more details, see:  uoguel.ph/equine-science-webinars

Value of strip grazing (and chance to win a strip grazing kit)

 Strip grazing can play a useful part in controlling horses’ weight a recent study has shown.

Strip grazing refers to reducing the amount of grass available by sectioning off a smaller area of the paddock using electric fencing. The fence is moved daily to provide gradual access to fresh grazing. A back fence may also be used which can be moved by the same amount to keep the overall grazing area the same size.

 

Restricting grass intake is an essential part of many weight management programmes, and the latest research on strip grazing shows that it can be an effective solution. For many horses and ponies, grass is the main source of calories in the diet and is also one of the hardest for owners to control. A 250kg pony living out at grass may consume enough energy (calories) to fuel a 500kg racehorse – equivalent to more than half a bag of conditioning cubes every day.

 

The study, comparing three restricted grazing practices for equine bodyweight management during the United Kingdom grass growing season, was conducted by Annette Longland in collaboration with SPILLERS via the WALTHAM Equine Studies Group.

 

Three groups of four ponies were turned out into individual paddocks that had been measured at the start of the study to provide 1.5% of the ponies’ bodyweight (dry matter) in grass, for 28 days. 

 

The ponies were assigned to one of three grazing practices: 

·       after a two-day adaptation period ponies were given access to the whole paddock with no restrictions; 

·       a lead fence was placed across the width of the paddock and after a two-day adaptation period, it was moved 1/26th of the remaining paddock length daily to allow access to fresh grass; 

·       after a two-day adaptation period a lead fence and a ‘back fence’ were moved by 1/26th of the remaining length every day.

 

Ponies with access to the whole paddock showed a significant increase in body condition score, but ponies in either of the strip grazed groups did not. The strip grazed ponies gained significantly less weight than ponies in the total allowance group, regardless of whether a back fence was used. In fact, strip grazing without a back fence was no less effective than strip grazing with a back fence, even though the grazing area got larger every day.

 

The WALTHAM Equine Studies Group, who provide the science behind the SPILLERS brand, have now published 100 research papers relating to obesity, laminitis, equine metabolic syndrome (EMS) and weight management. To celebrate, SPILLERS is giving one lucky horse owner the chance to win a strip grazing kit, including energiser, fencing tape and posts. The competition is running on the SPILLERS Facebook page from 21-28 June.

 

 

For more details, see:

 

Longland, AC, Barfoot, C, Harris, PA. 

Strip-grazing: Reduces pony dry matter intakes and changes in bodyweight and morphometrics. 

Equine Vet J. 2021; 00: 1– 8.

https://doi.org/10.1111/evj.13416