I am so confused about the least hazardous time to turn out my horses this time of year. I had both my fit Qurab (whose insulin test was high normal while I was recovering from surgey and went back down to low normal) and my super thin mini out for 1-1/2 hours first thing in the morning during the summer. I had hoped to get them out again for at least that long during the winter.  I had read to wait until a hard frost which seemed to be what my vet was recommending but then other things I've read have said not to turn out when the temp is below 40 F. Does that mean it's okay to wait until later in the day; i.e., not first thing, to put them out? The problem is that where I live it's not often below 41 at night.  And what about snow?  We don't tend to get much accumulation but it tends to hang around for quite awhile.  And then I read about not putting them out after a frosty night followed by sun.   It may be that some of what read relates to Fall and not Winter grass.  Anyway, my senior brain is spinning!  Can someone make this simple for me or is there some resource at there that says if it is doing this and that then don't turn out--like a decision tree?   Thank you.
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Julie D OR 2021
https://ecir.groups.io/g/CaseHistory/files/Julie%20and%20Porter

Hi, Julie. There are more reasons than ESC to consider when turning your horses out on grass. You can resolve some questions by doing the hard work of cutting a 100g sample of pasture grasses and having them analyzed. Just be aware that it’s almost impossible for an average horse owner to get accurate ESC values this way because the sugars in cut grass continue to to be hydrolyzed after cutting. That means ESC will be lower by the time the sample is frozen, shipped and tested. 

Another concern is what those grasses will do to your mineral balancing. Iron and manganese content can be very high in grass growing in water-saturated winter soils. 

Last, a big surprise to me was high nitrate content in perennial grasses during the winter. I shouldn’t have been surprised because our fields are heavily contaminated by invasive grass species known for high nitrates. They are the only grasses still green in dead winter. 
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Cass, Sonoma Co., CA 2012
ECIR Group Moderator
Cayuse and Diamond Case History Folder                
Cayuse Photos                Diamond Photos

Hi Julie, 

If it's above 40 deg F 24/7, then the grass is still able to metabolize the sugar it accumulates during photosynthesis the prior day and sugar concentrations shouldn't build up too much.  So the safest time to turn out is early in the morning after the grass has metabolized sugars all night (if temps are above 40) before the sun hits it in the morning, and/or all day on overcast or rainy days with no sun (again, if temps are above 40). 

Any lower temperatures and the risk gets much higher.  For example, if you have snow on the ground and sunny days, it is likely too cold for the grass to metabolize sugar, but if the grass has any green in it the sun will keep it photosynthesizing and sugars can build up fast.  Also, after a freeze when temps are cold and grass appears 'dead' or brown, sugars are being stored in the roots and keeping that plant alive so it can regrow in the spring, so if your horses eat down to the roots they are enjoying that sugary snack.

Cass has good points, including the possibility of high iron and manganese.  On the west coast we typically have acidic soils that love to concentrate iron and manganese in plants.  Manganese can also be very high because of the volcanic debris in soils.  A lot of horses with EMS on the west coast struggle with the grass and I don't think they do well grazing in this part of the world.

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Kirsten and Shaku (EMS + PPID) and Snickers (EMS) - 2019
Kitimat, BC, Canada
ECIR Group Moderator
Shaku's Case History
Shaku's Photo Album

Snickers' Case History
Snickers' Photo Album

Hi Julie
Your case history form doesn’t show recent insulin test results, but I noticed you mentioned “low normal”. Just a reminder that if you are thinking of the lab ranges as “normal”, that’s not the case. 

This is explained here: https://www.ecirhorse.org/FastingInsulin-LabRefRanges.php


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Maxine and Indy (PPID) and Dangles (PPID)

Canberra, Australia 2010
ECIR Primary Response

https://ecir.groups.io/g/CaseHistory/files/Maxine%20and%20Indy%20and%20Dangles 
https://ecir.groups.io/g/CaseHistory/album?id=933

 

Well, Porter likes this recommended test---getting to eat all night!  When I tested him in July 2021, his insulin level was 13.41 with a Reference Range of 10-40.  This was NOT fasting.  He would have had breakfast and I recall he grazed a few bites of grass before the blood draw but he did not eat all night long.  Does this result mean anything at all?

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Julie D OR 2021
https://ecir.groups.io/g/CaseHistory/files/Julie%20and%20Porter

Hi Julie
Did he have hay only for breakfast and how soon after breakfast was the test? There is a rise in blood glucose after the horse eats the first meal of the day, followed by an insulin spike. The insulin spike will be higher in a horse that has grain, lower in a horse who's had hay. After about four hours the insulin settles down, which is why we recommend waiting four hours after breakfast if the horse has nothing overnight. However, if Porter did the test within four hours of eating, the result could be falsely elevated, so that result is pretty good. 
That said, if they were mine, I'd get a more recent test done before risking them on any grass. If their results are good, you can go from there in deciding when and how long. I try to graze my mare straight after she's ridden/exercised, as an extra precaution.

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Maxine and Indy (PPID) and Dangles (PPID)

Canberra, Australia 2010
ECIR Primary Response

https://ecir.groups.io/g/CaseHistory/files/Maxine%20and%20Indy%20and%20Dangles 
https://ecir.groups.io/g/CaseHistory/album?id=933