That is exactly why I had all of the fields completely tilled and completely re-seeded with a mix that had certified tested fescue seeds. Then did the re-testing. I don’t even have pregnant mares, but I didn’t want to run into that issue down the road. Also yes I completely agree with the time. We always used to make sure that we cut our hay early morning. I’m thinking about sending in a soil sample to Logan labs here for mineral content too. I asked if anyone in the area had any issues with selenium poisoning (because of the studies I read about it happening more commonly in the Midwest). They think I’m crazy I guess? Everyone here seems to just feed the pre-mixed feeds. I was looking at the labels at the local feed store and some of them were pretty high in selenium which is great if your soil is low in selenium, but not if your soil is high. Although I even was told to “just feed sweet feed to keep the yearling weight on”. I might as well just bake my horses a sugar loaded cake at that point

I’m still having my soil tested for selenium levels. I noticed a lot of horses around here have brittle hair and hooves which could be many things, but I still have my selenium toxicity concerns. Based on the US soil data map our area is on the high side. I am a big Dr. Kellon fan I have been reading her work and articles since I was 13 and now I’m almost 30
That's crazy that people in your area just bale *whatever* and feed it to their horses! Even apart from toxic or nutritionally-useless weeds, who knows what chemicals end up in some ditch by the side of the road - definitely motor oil runoff and micro pieces of tires from the roads, maybe chemicals that the county sprays to keep the shoulders clear.
Interesting that your area is so high in selenium, here in the northwest our forage tends to be too low. I feed a vitamin/mineral supplement formulated for this area ("Northwest Horse Supplement") that is supposed to correct whatever mineral imbalances are in our soil - we get super nice tested hay grown in Eastern Washington, but not much you can do about the soil it's grown in, besides feed the right proportion of minerals. Still, I'd rather feed hay that I know is safe and have to supplement, than worry my hay has an unsafe level of something. Easier to add than subtract!
Sweet feed, LOL. Back in the day everybody fed COB, me included. My colt ended up having to have OCD surgery when he was 5, I know genetics adds to the likelihood, but I can't help but think too many calories compared to protein and roughage when they are still young contributed to it. I don't disagree with something like straight oats for a horse who's in heavy work, but never again will I feed anything containing corn or molasses to any horse of mine.
As far as grasses a lot will depend on your region. For grasses, I knew I absolutely did not want clover, limited rye and any fescue needed to be endophyte free. I settled on a mix that was Bluegrass, Orchard Grass, Timothy, Endophyte Free Fescue and was supposed to have only 1-2% alfalfa. Well that was a lie because my pasture is covered in alfalfa which I did not want. I have used seed mixes with as much as 20% alfalfa and I did not have as much alfalfa come up as I did with the supposed 1-2% alfalfa in the seed mix. Alfalfa has its place, but it’s one of those legume grasses that I think should be able to be used or removed from a horses diet as needed. I just don’t personally like to give my horses tons of alfalfa.
The only reason I brought up this old discussion about forage and feeding is because after reading some more recent research and discussing it with my vet, I was surprised to learn alfalfa is LOWER in sugars than orchard grass and even Timothy! Never would have guessed that!
So now both my older horses get about 2/3 alfalfa and 1/3 orchard grass for their hay. No actual "grains" at all, just rice bran pellets for my hard-keeper older OTTB mare, low-carb pellets for my 30-y-old gelding who has PPID (Cushing's) and I monitor their weight and add alfalfa pellets as needed. Both get the Northwest supplement that adds the needed selenium, enough phosphorus to keep the phosphorus/Calcium ratio within the 1:2- 1:6 requirements (due to the extra calcium in so much alfalfa) plus some vitamin E. I also ffed a biotin hoof supplement (my farrier laughed at me, but whatever, I believe it helps healthy hoof growth) Cosequin since they're both elderly, and a protein supplement to bring total protein for both of these oldsters to 16%.
Before we got my gelding's PPID under control with medication, his weight was fluctuating badly, and at one point I was loading him with soaked beet pulp. Really great food for weight gain, very low in sugars compared to sweet feed! But a pain to deal with every day, glad we got him stabilized with adding or subtracting alfalfa pellets.
And the vet cleared me to keep riding my OTTB mare, 26 years old!
But if I could go back in time to when I bought my 30-y-old gelding as a weanling, I would feed him a lot differently than I did then. Only Timothy and orchard grass for hay - total diet 12% protein or so, except when he was in growth spurt and looking leggy, add another 2-3% protein in the form of alfalfa or alfalfa pellets as needed. No feeds with corn, molasses, soy. Rice bran if he needed weight. Once he was in work starting at 4-5, maybe add straight oats if he needed energy to get fit.
I can't help but wonder ... if I'd fed him this way from the beginning: Monitoring the amount of protein according to his growth, supplementing protein only when needed.
Avoiding sugars like corn and molasses altogether, using healthier alternatives like rice bran or beet pulp when needed to maintain weight.
Only feeding limited grain (in the form of oats) when needed for energy, once he was 4-5 and starting to work...
Could I have prevented his OCD at age 5 and maybe even his PPID now? And still be riding him today, at 30? Lot's of 30-y-olds still do light work.
Wish I could go back in time, but we all live and learn, and my lovely old boy doesn't care really. He trots and canters around his (dry lot) paddock, flirting with the mares, prancing and snorting, showing off his beautiful movement, which is still light, forward and expressive, in spite of his PPID sway back.
I'm now going to read about Dr. Kellon's research, thanks for the link.