A write up from the European Society of Veterinary and Comparative Nutrition Congress (ESVCN) by Sharon Smith MSc SEBC(Reg) IEng BHSAPC. 

Introduction

The event, jointly hosted by the Waltham Centre for Pet Nutrition and the Royal Agricultural University, attracted an audience of nutritionists, vets, behaviourists, students and industry professionals.

Each of the 5 papers was written and presented by respected scientists in their field.  So, rather than regurgitate each one in turn, I’ll extract the common themes and also the subjects that caused disagreement or discussion in the room, as this is how we start assimilating the new findings with our own experience.

Equine Obesity and EMS

‘Equine Obesity and the Metabolic Syndrome: Challenges for Nutrition.’ got the day underway with Prof Caroline Argo - but every other presenter included obesity in their respective papers too, so I will return to this presentation throughout.  Between 41% and 55% of UK and USA leisure horses are obese.  Also, in the UK, the number of horses in work has fallen by about 20% - our horses and ponies are the equivalent of couch-potatoes.  As muscle is the end-of-the-line in the body for insulin-induced glucose (sugar): fitness; muscle type and amount of muscle are critical in how much of it can be burned off to reduce the risk of Insulin Dysregulation (ID).  Exercise, and the avoidance of high sugar and starch intake rates, is the key to avoiding ID, and ‘Equine Metabolic Syndrome’ (EMS).  This could all be summarised in the following diagram:

Diagram to show that Equine Metabolic Syndrome is the combined result of obesity, Insulin Dysregulation and Laminitis susceptibility (reproduced from memory of the PowerPoint presentation)

On its own, obesity does not mean the horse will have EMS or develop Insulin-related laminitis.  But, obesity leads to many other health issues, as it does in humans, such as concussive injury, but especially joint problems with increasing age.  Osteo-Arthritis is the main reason for euthanasia at a prominent horse welfare charity, by far, according to a later presentation about older horses by Prof Pat Harris of WALTHAM Centre for Pet Nutrition and MARS Horsecare. 

Prof Argo suggested weight reduction measures using dietary and routine adjustments.   These may be challenging for owners to implement.  Oral joint supplements are expensive, but easy to buy and administer – perhaps these could help the owner of an obese horse?  Dr Ingrid Vervuert presented a mini-review of the literature that highlighted the welfare concerns about such implied medical benefits. 

Oral joint supplements

In her review ‘Oral joint supplements in horses: Do they work?’, Dr Vervuert focussed on papers published in the last 15 years (2002 – 2017) under ‘real-life’ conditions.  I couldn’t help notice this was the only presentation not ‘Sponsored by…’.  In 2009 a team of researchers reviewed the quality of scientific study into glucosamine supplements.  Of 315 published papers, only 3 papers met 60% or more of accepted scientific criteria for meaningful interpretation of their results. These 3 studies reported no significant improvement.  The rest were not assessing efficacy under ‘real-life’ conditions. 

In reviewing hyaluronic acid, MSM, hydrolysed collagen, Omega-3 fatty acids, trace elements such as manganese and vitamin C, and herbal products including Devils Claw, the only meaningful evidence for improvement in lameness came from Omega-3 fatty acid supplementation in dogs.  Omega-3 hasn’t been of interest to horse studies, so there is no evidence of lameness improvement in equids, yet.  She concludes that, “evidence for efficacy of oral joint supplements is still equivocal [open to interpretation] as composition, experimental study design, material and methods are very variable”. 

Dr Vervuert highlighted how unreliable owner-surveys were.  The owners of a placebo / control group (i.e. unknowingly fed a substance that could not have been effective) saw the most improvement in their dog’s lameness – almost 1 point on a scale of 7.  I sat in on a presentation by a supplement company recently that almost boasted at the decimation of the natural resource of Devils Claw Root in Africa – they were selling so much of it.  Their conclusion was these things must work, or people wouldn’t buy it.  Today Dr Vervuert discussed how the placebo-effect could mean horses are returned to previous levels of ridden work when they are no better, especially competition horses that cannot be legally competed with pain-killers and NSAIDS in the bloodstream. 

Prof Harris asked Dr Vervuert what can be done for owners reluctant to feed NSAIDS for fear of gastric ulcers, but wanting to do the best by their horses?  The response was NSAIDS do not explain such high prevalence of EGUS and modern NSAIDS, when fed correctly, are unlikely to cause or gastric ulceration or make it worse.  Rather there was good evidence for efficacy of orthopaedic trimming/shoeing, adapted exercise programs (to the benefit the horse), and control of obesity.

Gastric Ulcers

Dr Nanna Luthersson supported Dr Vervuert’s opinion of NSAIDS in a presentation of her paper, co-authored with Prof. Harris, ‘How can we use current knowledge to reduce the risk of Equine Gastric Ulcers?’.  Equine Gastric Ulcer Syndrome (EGUS) is now divided into two specific diseases, based on the part of the stomach the ulcer is found:

• Equine Squamous Gastric Disease (ESGD) – ulceration of the upper part of the stomach, which can be easily avoided and successfully managed with increasing forage in the diet
• Equine Glandular Gastric Disease (EGGD) – ulceration of the lower part of the stomach, less well understood, found in around 50% of sports horses, and more difficult to treat through dietary change

Figure 2 – diagram of the equine stomach, showing acidity above and below the margo plicatus (blue line), location of ESGD and EGGD, and route of the gastroscope (black line) to be able to explore suspected EGGD, through the pyloris, into the duodenum.

The authors state:

1. pain relief
2. healing
3. prevention of secondary complications

…are the primary goals of anti-ulcer therapy.  Addressing pain-relief, Dr Luthersson returned to the NSAID discussion, recommending that owners could now access palatable formulations (I use a suxibuzone formulation, rather than phenylbutazone) that protect the stomach using a coating on the granules – so it must be consumed ‘dry’, ie not mixed in with wet food or water.  Dr Luthersson touched on one important subject I’ve been keeping track of recently, which is chronic pain recognition in horses and a study aiming to objectively describe a ‘pain face’.  Most owners would recognise clinical signs of chronic pain in horses they know: negative behaviour; lethargy; ‘aggression’ towards people and anything within reach of their teeth, along with other signs of a stomach upset such as ‘girthy’ behaviour and kicking out under saddle.  As EGGD is more difficult to detect than ESGD it is possible many horses live with pain.  My opinion is that, as horse owners and professionals, we MUST stop labelling negative horse behaviour to serve our own ego and an excuse for inaction, and start seeing their behaviour for what it REALLY is – struggling to cope with unresolved pain.

For healing, omeprazole medication for EGGD is most effective when fed to horses on an empty stomach, so best done first thing in the morning after the horse has finished their overnight forage ration.  It was then important to avoid feeding for an hour afterwards.  Omeprazole reduces stomach acidity, but there can be secondary complications.  The reduction in acidity may allow harmful bacteria to make existing ulcers worse – as evidenced by photographs presented by the Dr Luthersson – and requiring additional medication.

Once the ulceration is bought under control, the horse must have undergone dietary and management changes, or ulcers will reappear quite quickly.  The authors acknowledge the important role of forage in suggesting similar approaches in management and feeding practices for horses with either type of ulceration.  Many of the recommendations from Dr Luthersson and Prof Harris would fit perfectly for the obese horse weight-loss programme as these centred around providing a “Fat and Forage” diet as opposed to a “Grain and concentrate” approach, even for horse sin intense work, and avoiding prolonged periods (6h+) without feed.

Feeding straw

One of the recurrent threads running through the day was the inclusion of straw in the diet.  Straw has an energy value around half of hay and is often considered an alternative to soaking for calorie control.  The subject of ‘diluting’ the hay ration with straw was discussed after Prof Argo’s presentation as a way of avoiding restriction in Dry Matter below 1.5% in obese horses (which carries with it risks for Insulin Sensitive horses), with varying opinions expressed regarding suitability for equid diets.  Historically in Scotland, ‘straw was for ponies and hay for horses’.

Most concern was for impaction colic risk for 100% straw diets (except for donkeys – who should be few straw) and then ‘quality’ including residual grain/seed that may attract a hungry horse.  Also, Dr Luthersson and Prof Harris presented evidence the abrasive nature of straw increased the risk of EGGD (as well as stemmy/sharp alfalfa chaff, particularly in weanlings).  It was suggested there are good and bad quality straw, just as there is good and bad hay or haylage.  We need to be discerning consumers.  During other presentation, the room did not object to several suggestions that 30% of the hay ration for a horse could be replaced with straw, but the amount would need to be increased gradually – as with any new feed – and of good quality.  Straw can be steamed of course, which softens it, reduces microbial content, and makes it more palatable.  If my horse was diagnosed with EGGD I would avoid straw until the ulcers were healed.  Because he also has dental challenges I would need to be careful about selecting soft straw and would also steam it.

Forage quality and manipulation to suit the equid

‘Feed forage’ was a theme running throughout the day – along with obesity – demonstrating how important it is.  Prof Meriel Moore-Colyer focussed specifically on forage quality when presenting her paper, ‘Feeding Horses Forage: Health, Welfare and Diversity – the Essence of Life’ highlighting yet again the need to feed forage at least 1.5% of bodyweight as Dry Matter, but also pointing out the huge variability in quality of preserved forage and pasture.  She also explained the importance of where particular feeds were digested in the equine gut and how there was now strong evidence good quality forage sustains standardbred horses in intense training (energy requirements double maintenance) over more than 2 years.  As a ‘Forage Fan’, and someone who champions the under-marketed under-dog, I know feeding forage doesn’t have to be guess-work.  Stop buying joint supplements, for which there is no evidence, and spend our money on analysis instead? Farmers could make about £150 extra per field by charging a £1/large bale premium for analysed forage, suggested in this presentation, and my personal opinion is money spent on getting forage right, including proper steaming, is more money saved - because you then know what the diet is lacking and can supplement accordingly, and keep airways healthy.  Prof Moore-Colyer also said we should analyse our forage AS FED, including straw if it’s in the diet!

Caring for horses that can’t eat long-stem forage or pasture

Prof Harris gave a personal account of the challenge of keeping her own geriatric, and old (the two categories are different – she explains), mare healthy as part of her presentation, ‘The Old Horse: Life Stage Nutrition to Maximize Health’.  Horses and ponies can be old in years but still completely healthy, and fed as any other mature horse.  Horses with chronic health problems can be ‘geriatric’ at any age.   My own gelding is 22, arthritic, and has PPID.  He has gone from 1 dental rasp and clean per year, to 5 dental visits this last year - to address caries and reduce the risk of impacted feed causing dental problems.  Prof Harris confirmed PPID and dental problems were the two main clinical situations leading to weight-loss in the older horse, but again returned to equine obesity as possibly being as much of a threat to the aging horse in recent times.

Aside from needing a rug more often and dental issues, particular conditions that can go un-noticed, were highlighted by Prof Harris as challenging for geriatric horses:

• Pain in the temporohyoid joint (the jaw) and reluctance to chew
• Pain (again!) from osteo-arthritis and reluctance to stretch the head to the floor.
• Inflammation and infections including pain (!) from periodontal (gum) disease
• Acute or chronic diarrhoea
• Poor quality protein in the feed source (lacking lysine and threonine) which may be especially important for horses with PPID
• Increased insulin sensitivity – good news for fatter horses that need to lose weight but a greater risk of laminitis too.
• Increased risk of Inflammatory Airway Disease / Recurrent Airway Obstruction
• Heavy parasite burdens for equids with PPID

Prof Harris went on to explain suitable environments for older horses eg, raised feeding platforms – like those for dogs – and no stabling was heartily recommended, if a suitable flat paddock could be provided along with age-appropriate companions.  Grass would be preferable to hay for horses with poor dentition and weightloss and Prof Harris writes, ‘… access to grazing seems to be the most consistent way to promote a good body condition…’.   Geriatric horses could benefit from receiving vitamins and minerals at levels recommended for horse in light to moderate work.  Vitamin C especially.

I’ve recently learned about huge advances in equine dentistry, and we should now expect a similar process for horses as we experience at our dentist.  A thorough inspection, under sedation, is the only way to be sure of dental health.  Prof Harris advises if struggling to chew hay, or tear pasture, there can be reliance on multiple bucket meals – but at least 4 meals per day to avoid the 6h threshold for ESGD risk.  Fortunately, we can avoid grain-based feeds these days, but the owner should focus on finding the right feed for chronic health conditions: energy-levels; quality protein; vitamins and minerals - and it’s expensive!

Why risk Dry Matter restriction, when you really want energy reduction?

While several presenters were discussing extreme Dry Matter restriction to reduce fat deposition, or gut-fill in horses in intense work, perhaps down to 1.0% of bodyweight (under veterinary supervision), the risks were also highlighted - especially by soaking.  Soaking for more than 7 hours is known to reduce water-soluble carbohydrates by 30%, Ash (minerals) by 30% and Dry Matter by 20% - although these figures varied.  It seems a shame to soak out the nutrients you’ve purchased / grown, to then have to replace most of them, but needs-must.  If soaking, Prof Moore-Colyer pointed out the risk of culturing the bacteria present in the forage and previously Dr Luthersson had eluded the role of bacteria in horses being treated with omeprazole for EGGD.  Prof Moore-Colyer pointed out she was not suggesting the same bacteria were responsible, as we don’t have any evidence. Veterinary practitioners in the room pointed out their experience was that soaking was not causing bacterial problems in the equine gut, otherwise we would have more unhealthy horses.  But, as Dr Luthersson pointed out, 50% of ‘normal’ horses have been found to have undiagnosed EGGD.  I note there is evidence by McGreevy that ‘unresolvable behaviour’ is huge cause of wastage (by euthanasia) in Australian Thoroughbreds.  Considering the previous discussion of lack of recognition of chronic pain, we need further research.

Dr Argo pointed out that if restricting Dry Matter to 1.0% already, soaking can make weight loss rates dangerously high, with similar crash-diet impacts as in humans, e.g. loss of muscle mass, stress, and behavioural rebound, plus horses bedded on shavings are likely to attempt to ingest vast quantities and the likelihood of the horse going without feed for more than 6 hours increasing the risk of gastric ulcers. 

Therefore, to cover all the recommendations today for weight loss in obese horses while avoiding EGUS, reducing stress, reducing the likelihood of re-bound eating behaviour:

• Feed no grain-based concentrates
• Feed forage at 2% of bodyweight as Dry Matter (a ‘normal’ appetite)
• Low-energy hay can be diluted gradually with 30% good quality (soft) straw or chaff,
• Analyse the ration ‘as-fed’, eg. post-soaking if soaking
• Supplement with vitamins and minerals and quality protein
• High-temperature steam, to reduce microbial risk and avoid re-purchasing nutrients
• Employ slow-feeding devices to avoid prolonged periods without forage

….and EXERCISE if possible several times a week, to the point of sweating and heart-rate increase, but not to the point of risking distress and lameness, ie. a ‘couch-to-5K’ for horses!