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Iron: Is There a Link to Laminitis?

I (Nerida) want to start reviewing some information on the relationship between iron and inflammation. Dietary iron is thought by some to contribute to the incidence of laminitis in horses, with serum ferritin starting to be used as the measure of iron status.

I don’t know if this is the case, but in reading human literature, it seems the relationship between serum ferritin and inflammation is a bit of a case of chicken or the egg. Lots of information shows serum ferritin is elevated in humans with inflammatory disease and/or metabolic syndrome, but it is not clear what happened first; did serum ferritin rise and cause inflammation, or did inflammation and cell damage occur and cause elevated serum ferritin?

So I thought a good place to start is with a link for you to a review on serum ferritin. This article tells us that serum ferritin is actually a little protein ball, with a hollow centre (my words) where it keeps iron. Depending on how much iron is available in the body, the amount of iron inside the ferritin can vary a lot.

When serum ferritin is measured, it is the protein that is being measured, not the iron. So a serum ferritin measure tells you how many little protein balls are there but not how much iron they actually contain.

The other interesting thing to note is that ferritin is made within cells and is not made in the blood. So it seems that for ferritin to get into the blood it has to come out of the body’s cells (with very limited evidence if any, according to these authors, of any regulated ferritin secretion mechanism in mammals). This leads to the hypothesis that the elevated serum ferritin seen during inflammation is due to leakage from damaged cells into the blood.

The paper goes on to talk about the relationship between serum ferritin and liver iron stores, which are considered the gold standard for assessing body iron stores. While serum ferritin is usually related to liver iron in ‘normal humans’ that don’t have inflammatory disease, serum ferritin can both under and over-estimate liver iron stores where some form of inflammatory disease is at play.

Meaning it is not necessarily a good indicator of overall iron status. These authors suggest serum (‘soluble’) transferrin receptor (sTfR) as being much more useful.

Anyway, there is a lot to take in and I have only had one read over and would need to read it many times to fully appreciate all of the content. The simple point I want you to take away is that serum ferritin is not necessarily an indicator of iron overload from high dietary iron and may instead be an indicator of inflammation. Maybe the chicken came first… or was it the egg??

I’ll keep reviewing papers over the next several months! 

Here’s a direct link to the article mentioned above: https://pubs.rsc.org/en/Content/ArticleLanding/2014/MT/C3MT00347G

 

Questions? Comments?

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Teff Hay vs Rhodes Grass Hay

Teff Hay seems to have suddenly appeared 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, I wouldn’t be eager to swap. Here is why:

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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Do High Sugar Forages Make Horses Fatter?

This is a question we are often asked and my standard response has always been ‘well, it depends on the calorie content of the forage’, which has always then made me wonder about the relationship between forage NSC and digestible energy content.

In looking at 13 pasture samples from one farm it seems the higher the NSC content, the higher the digestible energy (calorie) content. The pastures shown here were all sampled between 11 am and 2 pm on the same day. They were all dried at the same time and all were analyzed by Equi-Analytical.

For interest I plotted the Digestible Energy (calorie) value against the pasture non-structural carbohydrate (NSC = starch + water soluble carbohydrates) content and while this certainly isn’t publishable data the trend is pretty clear for this particular set of pastures in that as NSC increases so does digestible energy… which makes very logical sense given the NSC is a source of calories so the more NSC, the more calories.

So perhaps my answer should be ‘yes, high NSC forages will make your horses fatter faster than low NSC forages!’. And therefore yes, it makes sense to feed a low NSC forage when you are trying to achieve weight loss or avoid weight gain in your easy keepers.

For some tips on feeding an easy keeper see https://feedxl.com/11-feeding-the-easy-keeper/

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Is Grain Free/Low Sugar, Low Starch Always the Way to Go for Horses?

Feeding grain free diets has grown in popularity in the last 10 years and there are certainly many benefits. BUT, need it always be the way to go? The answer is, it depends, but often no.

Horses with conditions like laminitis, PSSM tying up, PPID/Cushing’s, equine metabolic syndrome, insulin resistance etc MUST be fed a low sugar, low starch (or low non-structural carbohydrate; NSC) diet. Usually, to achieve low enough starch and sugar levels, these diets need to be grain free. One of the things FeedXL is great for is to help you sort out which feeds, forages and supplements are safe (low in starch and sugars; NSC) or not safe to feed horses with these conditions.

But for horses that don’t need low sugar, low starch diets to control diseases, as long as grain is FED SAFELY, grains can form a very valuable part of a ration! They are economical compared to high energy fibres like beet pulp (which are expensive in comparison), they provide a source of glucose that horses in heavy work can use to readily replenish muscle glycogen supplies, and they are palatable… horses love grains, so keeping horses in hard work eating on grain based feeds tends to be relatively simple provided the recipe is good!

So, as long as grains are well cooked (with the exception of oats which can be fed uncooked) and as long as you feed them in small meals (no more than 0.5 kg/100 kg BW, 0.5 lb/100 lb BW) they can form a very useful part of a horse’s diet. These are HUGE ‘as long as’ statements too… feed grains in the wrong way and things WILL go horribly wrong. But that is another story for another day.

The moral of this story is don’t fall into the trap of one-size-fits-all when it comes to grain free. 

There is more info here on why we cook grains for those of you who would like the details: https://feedxl.com/18-feed-cooked-grains/

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Teff Hay for Laminitic Horses

Over the last few years questions about teff (Eragrostis tef) hay and its suitability for laminitic horses have started to come up and it appears production of teff hay and therefore availability is on the rise. Here is a very mini review of the published research on teff hay in horses that we can find:

Recent Research on Teff Hay for Horses

Staniar et al 2010

These authors report non-structural carbohydrate (NSC) contents for teff of 5.4% in the ‘boot’ stage and 8.4% in the ‘late heading stage’ of plant maturity. Both really low NSC levels and well below the 10 – 12% threshold considered safe for laminitic horses. Variation between samples was also minimal which is also our experience with other C4 Type grasses like Rhodes for example.

Horses in this study ate 1.5% to 1.8% of their bodyweight in teff hay, with the lower intakes being on the more mature hay. Again, this is a good thing as horses on restricted diets are unlikely to eat this hay as fast as more palatable hays like alfalfa, so they should eat for longer periods of time for lower calorie intake.

McCown et al 2012

Report that when fed to horses unaccustomed to teff and given a choice of either teff and alfalfa or teff and timothy, their intake of teff is lower than their intake of alfalfa (no surprises there) and timothy. BUT, when given access to only teff, intake was about the same as timothy hay. So they don’t relish teff hay, but truly, this is a good thing as they are less likely to overeat it!

Askins et al 2017

These authors report that horses given free access to teff hay consumed 1.5% of their bodyweight per day which equated to 86% of maintenance calorie requirements. So the finding of lower intake on teff continues … hooray for teff!
This study also reports that resting glucose and insulin levels did not change over 10 days while the horses were fed teff. To keep this in context however, ryegrass hay (which can be very high in NSC) was fed as the control hay in this study and glucose and insulin levels also remained the same on this hay. Unfortunately the NSC content of the hays was not reported (yet!).

DeBoer et al 2017

In another recent study, these authors report that cool season (C3) perennial grasses (in this case orchardgrass, also known as cocksfoot and Kentucky bluegrass) had a significantly higher NSC content than teff pasture in summer and fall/autumn, however actual NSC content was not reported (this is just an abstract, hopefully the data will be fully published in future).

This research also looked at differences in plasma glucose levels in horses grazing either alfalfa, cool season (C3) grasses or teff and found that differences were minimal. However, we know that insulin resistant horses can maintain normal glucose levels, they just need a lot more insulin to achieve this. So just because differences in glucose levels were not apparent doesn’t mean there would not have been differences in insulin levels. These authors report that insulin levels will be reported in future research, so hopefully it is just a case of ‘watch this space’.

Summary

All in all, from the research available, teff appears to be suitable for laminitic horses and any other horses who need either a calorie restricted and/or NSC restricted diet. If you are going to feed teff hay though be sure to use FeedXL to balance the diet.

Teff, being a subtropical/warm season/C4 type grass does contain oxalate which will reduce calcium absorption by your horse and may lead to calcium deficiency if you don’t correctly balance the diets calcium to oxalate ratio (FeedXL will make sure you do this!). Teff, like almost all forages will also be low in trace-minerals and doesn’t contain great quality protein… so you will have a few gaps to fill. Of course testing your specific hay and uploading this to FeedXL will give you the best results in balancing your horse’s diet!

Finally, alfalfa/lucerne hay makes a great forage to feed alongside teff. Alfalfa is similarly low in NSC, but unlike teff is rich in quality protein and high in calcium to help offset the calcium binding tendency of the teff. They complement each other nicely.

If you need a low NSC forage, teff gets the thumbs up from us!

REFERENCES

Askins M.J., Palkovic A.G., Leppo K.A., Jones G.C. & Gill J.C. Effect of feeding teff hay on dry matter intake, digestible energy intake and resting insulin/glucose concentration in horses. Journal of Equine Veterinary Science 52, 45.

DeBoer M.L., Hathaway M.R., Kuhle K.J., Weber P.S.D., Sheaffer C.C., Wells M.S., Mottet R.S. & Martinson K.L. Glucose response of horses grazing alfalfa, cool-season perennial grasses and teff across seasons. Journal of Equine Veterinary Science 52, 79.

McCown S., Brummer M., Hayes S., Olson G., Smith S.R., Jr. & Lawrence L. Acceptability of Teff Hay by Horses. Journal of Equine Veterinary Science 32, 327-31.

Staniar W.B., Bussard J.R., Repard N.M., Hall M.H. & Burk A.O. (2010) Voluntary intake and digestibility of teff hay fed to horses1. J Anim Sci 88, 3296-303.

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