There is ongoing debate within the equine community regarding whether water-soluble carbohydrates (WSC) or ethanol soluble carbohydrates (ESC) hold greater significance when evaluating the safety of forages and feeds for horses prone to laminitis. When discussing or calculating non-structural carbohydrates (NSC) in a diet, FeedXL opts for the inclusion of (WSC) along with starch to determine NSC. Here’s the rationale behind this choice.
WSC encompasses simple sugars as well as fructans, whereas ESC solely represents the measurement of simple sugars.
Previously, it was believed that hindgut acidosis, resulting from fructan fermentation, was the primary cause of pasture-associated laminitis, similar to the effect of starch in grain overload. However, through research, it has been discovered that sustained high insulin levels are responsible for pasture-associated laminitis.
Nevertheless, can we conclude that the absorption of simple sugars, as measured by ESC, is solely responsible for the insulin response? While simple sugars directly impact insulin levels, there are two potential ways in which fructans could also influence the insulin response.
Firstly, fructans are carbohydrates with varying chain lengths, consisting of fructose sugar molecules joined together with a glucose molecule at the end. Although most of these fructose bonds are not broken down by a horse’s enzymes, it is believed that some fructans, particularly the shorter chain ones, may undergo acid hydrolysis in the stomach or microbial fermentation in the small intestine. This process produces simple sugars, namely fructose and glucose, which can be absorbed by the horse and contribute to an insulin response.
Secondly, undigested fructans pass into the hindgut, where they undergo rapid fermentation. This fermentation leads to a significant increase in bacteria that preferentially ferment fructans, resulting in the production of lactic acid. The change in hindgut environment, becoming more acidic, causes a shift in microbial populations and reduces the diversity of microbes, including the desirable fiber-fermenting ones. While research in this area is still in its early stages, it is plausible that hindgut microbes can influence the insulin response, similar to humans.
Using ESC to calculate NSC may underestimate NSC and ignore fructans, potentially putting your horse at risk.
Hence, FeedXL recommends and uses the more conservative approach by considering WSC when examining the NSC component of forages (NSC = WSC + Starch). This approach is more conservative because WSC values are consistently higher than ESC values and still aligns with the principle of minimizing insulin spikes by limiting dietary simple sugars. Additionally, by maintaining low fructan levels in the diet, the negative impact on hindgut microbial populations caused by fructan fermentation is minimized, indirectly influencing the insulin response.
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With pasture sometimes forming the majority, if not all, of our horse’s diets, it’s important to enter pasture quality as accurately as you can in FeedXL.
Pasture quality corresponds with the amount of digestible energy, crude protein, macro minerals and vitamins your pasture is providing. Therefore, pasture quality determines what else you may (or may not) need to supply in your horse’s diet to meet their nutritional requirements.
We like to keep it simple when it comes to deciding pasture quality – by looking at colour and presence or absence of seed heads (basically stage of maturity). When pasture is overgrazed (less than 1 inch in height), it’s unlikely you’ll see any seed heads, therefore colour is your major guide.
So, next time you’re entering your pasture use the definitions and images below to help you determine quality.
Pasture Quality
Overgrazed
Excellent
Green
Actively growing
Very leafy
Virtually no flowers or seed heads visible
Good
Green
May or may not be actively growing
Flowers and/or seed heads are present
Plants are beginning to mature and become stemmy
Average
Green to yellow or brown
Most plants are stemmy and/or have visible flowers and/or seed heads present
Poor
Completely brown
Plants are stemmy and/or have visible seed heads present
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Oaten hay is commonly fed to horses. Recent research by Jackson et al (2018)1 suggests however that we should be cautious with oaten hay as it may be negatively affecting our horses’ dental health!
The Study
Dr Kirsten Jackson (https://dentalvet.com.au) and her co-researchers found in a study of 500 Western Australian horses, that oaten hay was significantly associated with an increased incidence of dental caries (tooth decay).
Image credit: Dr Kirsten Jackson (https://dentalvet.com.au)
How does Oaten Hay do this?
Dental caries form when bacteria in your horse’s mouth metabolise sugars in the hay/ feed and produce the by-product of acid. This acid demineralises the teeth causing decay which in horses generally means the outer layer (cementum) is stripped from the teeth.
Because oaten hay can be so high in water soluble carbohydrates (WSC; also loosely called ‘sugars’) the oaten hay feeds the oral bacteria, a lot… and then they produce a lot of acid… and the acid demineralizes (eats away) the hard part of the teeth.
It is thought that the near constant supply of sugars to the bacteria in the mouth when a horse has constant access to oaten hay, and therefore the prolonged periods of exposure of the teeth to the acids produced by the bacteria is what puts horses on oaten hay at higher risk of disease.
What about other types of hay or pasture?
Dr Jackson reports that in the same study it was found that a meadow hay based diet was protective. And horses with access to good quality grazing all year round were less likely to have peripheral caries than horses that had no access to grazing.
Other similarly high WSC hays like ryegrass hay and other cereal hays like barley and wheaten hay will potentially put horses at the same risk as oaten hay.
What can be done if my horse has dental caries?
The good news is that because a horse’s teeth are constantly erupting, and the acid produced when high WSC hay is fed only affects the part of the tooth that is physically exposed to it (so the tooth below the gumline remains unaffected), dental caries can be treated.
Jackson et al 2021 showed that when oaten hay was swapped for a lower WSC meadow hay, it allowed teeth to start to recover.
The authors note that full recovery generally takes around 2 years.
Image credit: Dr Kirsten Jackson (https://dentalvet.com.au)
Should oaten and other high WSC hays be completely avoided?
Not necessarily. It seems in this study that it was horses with free access to oaten hay that were most affected.
If you are in an area where other type of hay is difficult to source and using SOME oaten hay helps to get you through, then using some, mixed with a variety of other hays and/or access to pasture is potentially OK.
Also not all horses on oaten hay were affected so there is some individual variability in susceptibility to the caries so some horses can be ok on oaten but if your horse has caries it is best to avoid it. If your horse is on oaten hay and this can’t be avoided it is probably a good idea you have regular veterinary dental examinations conducted every 6 months.
If you are spoilt for choice with hay and can avoid oaten hay, you are probably best to avoid it completely… especially if you have a thoroughbred as they were also shown to be at higher risk!
References
1. Jackson, K., E. Kelty, and M. Tennant, Equine peripheral dental caries: An epidemiological survey assessing prevalence and possible risk factors in Western Australian horses. Equine Vet J 2018. 50(1):79-84.
2. Jackson, K., E. Kelty, and M. Tennant, Retrospective case review investigating the effect of replacing oaten hay with a non-cereal hay on equine peripheral caries in 42 cases. Equine Vet J 2021. 53(6):1105-1111.
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Straw is gaining favouritism among nutritionists and horse owners as part of diets for easy keepers. It allows energy intake of the diet to be reduced without drastic restriction in a horse’s daily feed intake.
This strategy is thought to improve the welfare of easy keepers and reduce the risk of colic and gastric ulceration, all common issues seen with feed restriction.
A recent study that substituted 50% of the grass haylage component of the diet with straw, further supports the use of straw in easy keeper diets.
The main findings in the study (Jansson et al 2021) were that the 50% straw diet had:
No effect on squamous or glandular gastric ulcers scores
Longer feed intake times and lower energy intakes
Lower Insulin concentrations (a positive for those prone to laminitis)
A trend for higher serotonin levels (a key hormone that stabilises mood; inhibits aggression, fear and stress; supports intestinal motility; plays a role in fat tissue metabolism)
Gut sounds that reflected normal motility patterns and no changes in manure moisture content– indicating no major adverse effects on gut function.
Why Should You Consider Including Straw?
It is now widely accepted that horses should be eating a minimum of 1.5% of their bodyweight in forage per day (dry matter basis). This supports natural behaviour and minimises the risk of health complications such as gastric ulcers and colic.
However, for some easy keepers, this amount of forage alone can exceed energy requirements. Therefore, replacing some higher energy forage in the diet with low energy straw can allow owners of easy keepers to reduce the energy content of the diet without restricting intake below 1.5% of bodyweight.
More bulk. Less energy! Happier horses!!
Isn’t There a Risk of Gastric Ulcers on Straw Diets?
A previous study published in 2009 reported the incidence of gastric ulcers (both glandular and squamous) was increased in horses fed straw as their only roughage source. The authors (many of which are the same authors on the above-mentioned paper) suggested that mechanical damage, changes in the gastric contents, specifically the fibre ‘mat’ that forms in the stomach, and reduced buffering capacity due to low calcium and protein content of straw could have been the cause.
However, in the present study the severity and incidence of gastric ulcers decreased over the study period (2 x 21 days). This suggests that including up to 50% of the forage in diets as straw does not increase the risk of gastric ulceration.
And in fact the slower intake of straw is likely to be a good strategy for ensuring horses don’t go longer than 4 hours without feed. Which should then act to reduce the risk of ulcers.
Decreased Feed Intake, No Time Without Forage
The 50% straw diet offered in 2021 study contained the same amount of energy as the haylage only diet. This meant that horses on the straw diet were receiving more forage (based on dry matter) than the haylage diet.
However, the researchers found that the horses on the straw diet actually had leftovers which resulted in them consuming less energy each day (10.7MJ per 100kg bodyweight) compared with the haylage group (12.4MJ per 100kg bodyweight).
This suggests that because horses are ‘fuller’ or more satisfied on the straw diet, they are likely to eat less forage which may decrease energy intake without the need for intake restriction.
Longer Periods Spent Eating
Another benefit of the 50% straw diet was that horses spent more time eating each day compared with the haylage only diet. The authors calculated that the horses on the straw diet spent 11.2 hours per 24 hours eating whereas the control diet horses spent 6.2 hour per 24 hours eating – an 80% difference!
The most likely explanation is differences in palatability or some physiological response as the NDF (measure of the cell wall components such as hemicellulose, cellulose and lignin) content of the two diets was very similar – NDF content is correlated to intake.
The authors noted that interestingly, the horses on the straw diet spent more time pausing their feed intake whereas the haylage diet was consumed almost at all at once.
Lower Insulin Response
Many easy keepers are at increased risk of laminitis. It is therefore in our best interest to feed a low sugar and starch diet which limits glucose and insulin responses.
In the present study, the insulin response was lower on the 50% straw diet than the haylage only diet. The total water-soluble carbohydrate (WSC) intake was significantly lower for the straw diet (60g vs. 75g per 100kg bodyweight) so this was not unexpected but does highlight another possible advantage of including straw in diets.
Be mindful that this cannot necessarily be generalised for all straw and analysis is recommended to determine the actual starch and WSC content of any straw you might consider using.
Also interesting to note that the grass forages used in this study were by no means high in WSC, being 7.7% and 4.9%, as compared with the straw being 0.8%.
Higher Serotonin Levels in Horses on the 50% Straw Diet
This is super interesting and the authors offered the explanation that chewing more and being more satisfied from a hunger perspective is potentially increasing serotonin levels and may be the reason why horses are eating less and taking more pauses between eating when offered the 50% straw diet.
It is well known in humans that spending longer chewing meals reduces hunger levels, with chewing stimulating serotonin.
Does Feeding Straw Increase the Risk of Impaction Colic?
The present study showed no difference in gut sounds between the haylage only diet and the diet with 50% inclusion of straw over the 21-day study periods. Nor did the moisture content of the manure vary between the two groups.
A lack of faecal moisture (or in other words, the presence of dry manure) may indicate increased risk of impaction colic. The authors noted that certain individuals and even some breeds are more prone to impactions and owners should be cautious.
All changes in forages should be made gradually over several weeks to minimise the risk of colic providing a chance for fibre digesting bacteria to adapt.
No More HANGRY Horses?!
Using straw in diets can add another string to our bow for managing the weight and seemingly insatiable appetite of easy keepers.
The results of this study suggest that inclusion of up to 50% of the forage ration as straw does not cause gastric ulcers and may in fact improve the welfare of easy keepers by reducing energy intake on ad lib hay and prolonging the time they spend eating.
Straw in effect lets us feed more bulk, while providing less energy. And keeps our horses fuller, happier, chewing for longer and less stressed!
Jansson, A., Harris, P., Davey, S.L., Luthersson, N., Ragnarsson, S.and Ringmark, S. Straw as an Alternative to Grass Forage in Horses—Effects on Post-Prandial Metabolic Profile, Energy Intake, Behaviour and Gastric Ulceration. Animals, 2021, Issue 11, Volume 8, Pages 2197-2211.
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I was honoured to have been part of the team who put together the Veterinary Clinics | Equine Practice book of clinical review articles on Equine Nutrition.
Together with Dr Brian Nielsen (Professor, Michigan State University) and Dr Carrie Finno (Associate Professor, UC Davis) we wrote the chapter ‘Nutritional and Non-nutritional Aspects of Forage’.
Hopefully it will make a great resource for equine veterinarians around the world!
The biggest take-home message…
Forage alone is unlikely to meet all nutrient requirements and some form of supplementation, be it in the form of supplements, balancers or feeds, will almost always be necessary to create a balanced diet!
If anyone would like a copy we would be happy to email it to you.
Richards N, Nielsen BD, Finno CJ. Nutritional and Non-nutritional Aspects of Forage. Vet Clin North Am Equine Pract. 2021 Apr;37(1):43-61. doi: 10.1016/j.cveq.2020.12.002. PMID: 33820609.
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Question: Can you touch base about grass and legume type hays, what each grass/legume benefits the horse’s overall health. Is a certain mixture better (or preferred) for certain horses; pasture pet, light work, moderate-heavy work, hard keeper, easy keeper, etc.
Example: benefits of having mixtures – pros to having certain types within the mix such as Birdsfoot Tree foil, orchard grass, climax timothy, Kentucky blue grass, spring green felstulolium, brome.
Watch the video below with FeedXL founder Dr Nerida Richards and SmartPak’s Dr Lydia Gray for the answer!
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Question: When feeding a lot of alfalfa, what is the best way to keep a horse’s Calcium to Phosphorus ratio where it should be?
Watch the video below with FeedXL founder Dr Nerida Richards and SmartPak’s Dr Lydia Gray for the answer!
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This is something we often hear… and 99% of the time it is WRONG!
Forages are (almost) always too low in trace minerals to meet a horse’s requirements and leaving them un-supplemented on forage only diets usually results in problems with their hooves, joints, immune system, muscles … everything really!
They may look OK, but there is usually a bunch of stuff going on inside that you can’t see until a deficiency is quite pronounced.
BUT, there are always exceptions to the rule and here is one example. This is a pasture from New Zealand that is able to meet all trace mineral requirements without any additional supplementation.
Even for selenium, which is something we don’t expect in New Zealand!
Sodium is a bit low (nothing unusual there) and iodine was not tested, but the fact is it is actually a pasture that horses would do OK on without extra supplementation. Just need a bit of iodised salt!
The horses on this pasture were being fed a selenium-containing balancer pellet and recently tested with blood selenium levels just in the high range (nothing scary, just high).
The lesson in this, forage analysis is a wonderful tool when assessing your horse’s diet and FeedXL makes it so super easy to really see what forage is providing and what you need to add, which in this case is very little.
If you’d like to have your forage tested, we love to recommend Equi-Analytical.
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Setaria should really be classified as toxic for horses. It is a subtropical pasture with such high levels of oxalate that it makes it almost impossible to prevent Secondary Nutritional Hyperparathyroidism (Bighead disease) in horses grazing this grass.
Grasses like kikuyu and buffel grass readily cause bighead disease with an oxalate content of around 15 g/kg. Setaria contains anywhere between 30 and 80 grams of oxalate per kg of (90% dry matter) pasture… which translates to HUGE amounts of calcium being needed to balance the calcium to oxalate ratio to prevent bighead.
We have seen horses go from normal to severely affected in a matter of months on setaria. So if you have setaria in your pasture you need to be very aware of what you are feeding and how well this is meeting calcium (as well as phosphorus and magnesium) requirements.
FeedXL will help you in calculating the calcium to oxalate, calcium to phosphorus and calcium to magnesium ratios to keep your horse healthy. BUT, the first step is identifying that you have this grass in the first place so you know you need to be on your game with managing nutrition!
Here are some photos (below) of setaria on the NSW mid-north coast… setaria everywhere! Please take a look at the photos and then in your paddocks to see if you have setaria. And if you do, please do something sooner than later to prevent severe and often life-threatening calcium deficiency.
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Teff Hay seems to be gaining popularity as a hay option for many horse owners and because it is sold as a low starch low sugar hay it is starting to be recommended in place of Rhodes Grass Hay.
BUT, if you are lucky enough to have access to Rhodes Grass Hay, here are some things to think about before considering a swap:
1. Rhodes Grass Hay is low in oxalate, containing approximately 2.5 to 3 g/kg of oxalate.
Teff Hay is moderate to high in oxalate at 10 to 12 g/kg. This means Teff needs careful supplementation of calcium, phosphorus and magnesium to prevent it from causing Bighead Disease. With Rhodes being so low in oxalate Bighead is not an issue (though you do still need to make sure you correctly balance the diet for minerals and vitamins as forages rarely contain enough to meet a horse’s requirement).
2. Rhodes Grass Hay is more reliable and consistent when it comes to the low starch, low sugar characteristic.
From the analyses we have seen coming through here at FeedXL Teff can be high in starch, with one analysis sent through showing an as-fed starch content of 7.1% and total NSC of of 13.7% which for a laminitic horse is going to be too high. While soaking would more than likely bring this non-structural carbohydrate (NSC) level back down to safe levels it makes for much more time consuming feeding… so if you have access to Rhodes Grass it would be much easier to use this.
3. Teff Hay causes some odd behavioural issues in some horses and this is normally associated with an alkaline fecal pH.
We have no way of explaining this, and it doesn’t happen with all horses on Teff so I don’t know if all Teff Hay is the same or if there is a certain variety that causes this issue.
So while Teff gives people in cooler climates a low NSC option which is welcome, it is not yet well understood and not without its issues. If I had a choice between Teff and Rhodes I would go with Rhodes Hay every time.
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