How much grass can a horse eat in one hour?

[Scribbler]

Found myself wondering about this as our first grass is just starting to come up, and marsey is delighted to search for every last blade.

Come summer, we will have some nice pockets of grass for attended grass-walks. Not possible to turn her out in them and leave, and one hour is about my limit for standing around watching her eat.

Assuming a maximum grass situation and a maximally food-oriented horse, how much is she putting away in one hour? Four foot tall grass in June, horse doesn’t even have to reach for it, can just stand in one place and wolf down what’s in front of her nose. And does this without barely pausing for breath

How much is she actually taking in, compared to hay? Would this be equal to a flake (three pounds)? It doesn’t really look like it ends up being that much food.

[Palm_Beach]

Mare: Not enough!!!

Owner: Too much!!!

The problem is that new grass is mostly leaf, so the horse is getting a lot of sugar. Mature grass is stemmy, so has lots of fiber. It’s really impossible to tell, so if you are worried about founder, put a muzzle on her.

[Texarkana]

The “accepted” number thrown around is that horses grazing generally take in 1-1.5 pounds per hour, on a dry matter basis. Of course, there’s a lot of things that affect that number.

[danacat]

The best times to graze (hand grazing too) are in the morning before 10:00…and at night (after the sun has been down for at least several hours). The sugar in spring grass (all grass really) is reduced at that time-- dead of night it’s even more reduced.

The problem with spring grass is that it is trying to recover and produce seed-- unlike mid-summer grass-- and the sugar content is sky high.

I would start with 15 minutes at most. Then work your way up from there. Also, horses that are getting regular exercise (from being ridden–not just turn-out) are less prone to founder. Exercise is pretty key!

Interestingly, a recent study (that my vet told me about) showed that laminitis/founder is really a crap shoot – that certain horses, regardless of breed, will founder where others will not, even when they are in the same ‘founder’ causing situation. It’s in the horse’s genes, so to speak, as to whether or not they will founder or and/or are prone to it.

Unfortunately there is no way to know…yet, from a science stand point…what category our horses fall into. Hopefully researchers will be able to create a test that will determine this. But for now we must be diligent and assume that any horse can founder, especially those easy keepers who are of the more cold blooded, slower metabolism type breeds.

[Katy_Watts]

[QUOTE=danacat;8548512]

Unfortunately there is no way to know…yet, from a science stand point…what category our horses fall into. Hopefully researchers will be able to create a test that will determine this. [/QUOTE]

This test is the best we have now to determine which horse is prone to laminitis.
http://www.chronofhorse.com/forum/showthread.php?479468-Testing-for-IR&highlight=insulin+testing

[JB]

[QUOTE=Texarkana;8547975]
The “accepted” number thrown around is that horses grazing generally take in 1-1.5 pounds per hour, on a dry matter basis. Of course, there’s a lot of things that affect that number.[/QUOTE]
Yep, this. Roughly 4-5ish lb of grass (as eaten) an hour, assuming at least moderately lush grass. Some could scarf more, others would nibble less.

Then given that grass is generically about 25% dry matter, you get that ^ number.

But July grass (here anyway) would be more dry matter, and April grass less dry matter.

The horse who only gets an hour on grass might well just snarf up all he can get, getting into the 6-7lb range, maybe even 8 if it’s lush enough, where those out all the time wouldn’t typically eat that much.

[Scribbler]

I wasn’t worried about founder, actually. She isn’t prone to it, she has lived on pasture year round before, and she is at a good weight, fit, ridden every day. And by the time June comes around, we’ll have been on lots of grass walks with sparser grass coming up.

I was more wondering whether one hour could add anything significant to her diet or nutrition. By the time the grass gets that tall, it is fairly stalky.

… Okay, I was googling around for photos of the stuff. Reed canary grass, a pasture grass that is invasive to wetlands. And then I found a whole new thing to worry about . Apparently some strains of reed canary grass in some regions carry potentially toxic levels of alkaloids, and in New Zealand caused the death of sheep. I have never heard of this in the PNW, and given how common this grass is here, I would think if it was a problem, it would have shown up by now.

At least I hope so.

[Montanas_Girl]

[QUOTE=Texarkana;8547975]
The “accepted” number thrown around is that horses grazing generally take in 1-1.5 pounds per hour, on a dry matter basis. Of course, there’s a lot of things that affect that number.[/QUOTE]

My graduate mentor always told us that, given plenty of forage availability, horses will consume roughly 1 kg DM/hour. This is about twice the value you’ve given. Can you provide a source for your number? I’m not arguing, just curious.

[danacat]

[QUOTE=Katy Watts;8548620]
This test is the best we have now to determine which horse is prone to laminitis.
http://www.chronofhorse.com/forum/showthread.php?479468-Testing-for-IR&highlight=insulin+testing[/QUOTE]

Yes…good test for some…at least an indication of IR. I tested one of my horses (a quarter horse) years ago with this test. Horse was neg. and that negative test gave me a false sense of security. Even on very minimal grass, he eventually became laminitic. My fault though too.

[Katy_Watts]

[QUOTE=danacat;8550505]
Yes…good test for some…at least an indication of IR. I tested one of my horses (a quarter horse) years ago with this test. Horse was neg. and that negative test gave me a false sense of security. Even on very minimal grass, he eventually became laminitic. My fault though too.[/QUOTE]

Sorry to hear. For clarification, your horse had a false negative with the test where they dose with karo syrup and pull blood to test for insulin after the glucose challange?

[JB]

[QUOTE=Montanas_Girl;8550449]
My graduate mentor always told us that, given plenty of forage availability, horses will consume roughly 1 kg DM/hour. This is about twice the value you’ve given. Can you provide a source for your number? I’m not arguing, just curious.[/QUOTE]

“So, how much grass can be eaten per hour of grazing activity? This will vary with pasture forage quantity, quality, and palatability, and also with the amount of time horses are on pasture. However, about 1-1.4 pounds (0.5-0.6 kg) per hour (DM basis) is a reasonable range assuming quantity is not a limiting factor.”
http://www.thehorse.com/articles/13696/pasture-grass-the-healthy-choice

"Horses will generally eat about 1-1.4 lbs of pasture grasses and legumes per hour on a dry matter basis if they have enough pasture available. "
http://animalscience.uconn.edu/extension/publications/pastureexist.htm

“Kiley-Worthington (1987) reported that a horse of about 500 kg will eat around 13.5 kg of fibrous material over24 hours, provided free access, with variation depending on physiological demands.”
http://lib.ugent.be/fulltxt/RUG01/002/062/802/RUG01-002062802_2013_0001_AC.pdf

[Montanas_Girl]

Thanks, JB! I’m curious as to why those numbers conflict with what I was taught. I’ll have to get in touch with my mentor and investigate her sources. She literally “wrote the book” on equine nutrition (was the head of the last NRC committee), so I’m intrigued by the discrepancy.

[JB]

That is really odd that her numbers are double what every other source I’ve seen has. Could it have been a translation error? 2.2lb/hour would mean 35lb of dry matter for that 1100lb horse

[Montanas_Girl]

I’m not sure where the discrepancy is coming from, but I will definitely look into the question. It could be that she is/was referring to horses who are turned out for limited periods of time (2-12 hours) vs. 24/7, although 35 lbs of DM in 24 hours wouldn’t be completely unrealistic for a 1200 lb horse in 24 hours (3.5% of body weight being our assumed upper limit for voluntary DM consumption)…Recent research has indicated that horses on restricted turnout/forage availability will eat just as much in their limited time period as those out during a 24 hour period, so that could be contributing.

I will let you know if I can dig up additional information!

[Texarkana]

I think the discrepancy comes from the difference in turnout/pasture access. Because I seem to recall seeing the 1kg/hour DMI as more of an upper limit number. There is certainly data out there that horses approach that number when turned out on a limited basis. For example, these:

http://www.j-evs.com/article/S0737-0806(11)00387-X/abstract

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwiyuunn0ZnLAhWDbiYKHVhADWcQFggcMAA&url=http%3A%2F%2Fwww.bsas.org.uk%2Fwp-content%2Fthemes%2Fbsas%2Fproceedings%2FPdf2005%2F109.pdf&usg=AFQjCNHnTEWLq3debWS8bRm1dQNZuH1vRg&sig2=kmlXX8HdtDojeciQdXaLsQ&bvm=bv.115339255,d.eWE

I also now suspect, thanks to this conversation, that the 1-1.5lb/hr number that is tossed around so frequently might be calculated as an hourly average based on total daily DMI and not a hard measurement per hour. I only say that because I tried to find the origin of the number by tracing back the citations. They all seem to go back to references that state horses will graze 15-17 hours daily and take in ~1.5% to 3% of their body weight in dry matter. Of course, I’m operating on limited access to the literature here at home.

[danacat]

[QUOTE=Katy Watts;8550533]
Sorry to hear. For clarification, your horse had a false negative with the test where they dose with karo syrup and pull blood to test for insulin after the glucose challange?[/QUOTE]

No…no dosing with syrup…must have been a completely different test. If I remember correctly: just a blood test of some sort. Hmmmm. Guess vet should have done the test you mentioned. Grrrr!

[Katy_Watts]

It’s a brand new study, so only vets who work to stay current will get it. Lots of good new stuff the last 10 years.
A lot of horses that fit the type for high insulin were not testing positive with fasting tests. So they came up with a ‘challenge’ test- dose with the syrup and then test response. The discovery in humans, and now horses, that factors in the intestines are part of the insulin disregulation, is now prompting researchers to test response to feeding, rather than baseline insulin after fasting. ID is the new designation instead of IR.

search ‘toll-like receptors metabolic syndrome’.

[danacat]

[QUOTE=Katy Watts;8551444]
It’s a brand new study, so only vets who work to stay current will get it. Lots of good new stuff the last 10 years.
A lot of horses that fit the type for high insulin were not testing positive with fasting tests. So they came up with a ‘challenge’ test- dose with the syrup and then test response. The discovery in humans, and now horses, that factors in the intestines are part of the insulin disregulation, is now prompting researchers to test response to feeding, rather than baseline insulin after fasting. ID is the new designation instead of IR.

search ‘toll-like receptors metabolic syndrome’.[/QUOTE]

Thank you! Good to know.

[JB]

35lb DM in the form of grass becomes something like 140lb of grass, assuming 25% DM. That’s just an enormous amount to consume on average. I suppose I could see that if a horse is on a well-stocked pasture in August, where DM is much higher than that same pasture in April or May.

It’s totally within reason for horses who are on limited turnout, and for spurts of time for horses out longer but on really lush grass.

So yes, I can see that as short-term upper limits, but not an average for horses turned out full time on pasture that would sustain that.