Your monthly intel on equine nutrition, health, and performance — from working horsemen.From Mane Metrics
The Top Line · What's Worth Knowing
Four findings that change how you feed this month
15 mg of boron a day built faster-growing, stronger Arabian foals in a new 90-day trial.
Pasture-fed horses are running low on selenium — 211-horse Spanish study confirms.
Broodmares on a daily nutrient mix had +16% better embryo recovery in a 2026 crossover.
We settle the hair-vs-blood-vs-forage debate. Spoiler: each answers a different question.
★ Lead Feature · Trace Minerals
The Boron Breakthrough
A trace mineral most owners have never heard of just earned its seat at the breeding-farm dinner table.
The setup. A new study from Türkiye gave 32 Arabian foals one of four daily doses for 90 days: zero, 5 mg, 10 mg, or 15 mg of boron. Researchers tracked weight gain, blood chemistry, and bone-building markers throughout.
The findings. Foals on 15 mg/day gained more weight per pound of feed, ran higher blood calcium, and posted stronger bone-formation markers than the no-boron controls. The 15 mg group grew faster and built denser bone than every other group.
Why it matters. Boron is a trace mineral — horses need only a tiny amount, but they need it. It helps the body use calcium and magnesium. Without enough, bone and joint health suffer. Human research has long linked low boron to weak bones and arthritis. The horse research is now catching up.
The catch. Most feed tags don't list boron. Most supplements don't either. Hay and pasture can have plenty — or almost none, depending on the soil. The bag won't tell you. This is where hair mineral analysis earns its keep — a 42-element panel will show you exactly where your horse stands on boron and every other trace mineral. If you're already noticing a weak topline, this is your starting point.
Bottom line: If you have a foal, a yearling, or any horse with bone or joint trouble, ask your vet about boron. Test before you supplement — too little does nothing, too much causes problems.
Yilmaz et al., 2026. Biological Trace Element Research. DOI: 10.1007/s12011-026-05138-x
◆ Mineral Spotlight · Selenium
Pasture Horses Are Running Low on Selenium
If your horse spends most of his day on grass, this one matters.
The data. A 211-horse study from northwest Spain measured 14 minerals in the blood across breed, age, sex, and diet. One finding popped: horses on pasture diets had lower selenium than horses fed commercial grain. Many tested at or near the bottom of the healthy range.
Why selenium matters. It's a powerful antioxidant that protects muscle cells from damage during work. Low selenium shows up as slow recovery, muscle stiffness or tying-up, weak immune response, dull coat, and reproductive trouble.
Hair loss · cracked hooves · weight loss · lameness. Toxicity is real and not rare on supplements.
The tricky part. Selenium has the narrowest safety window of any mineral. Too little is bad. Too much is toxic. You can't dump a scoop in and hope — and a one-time blood draw only shows you the moment.
Bottom line: If your horse lives mostly on grass, don't assume he's getting enough. Hair testing tracks selenium over 90 days — far more useful than a single blood snapshot.
Fernández-Villa et al., 2026. Journal of Equine Veterinary Science. DOI: 10.1016/j.jevs.2026.105846
♀ Breeding Brief
L-Citrulline for Broodmares: More Milk, Bigger Foals
Lactating mares burn through nutrients fast. A new study from China tested whether a single amino acid — L-citrulline — could lighten the load.
Researchers split 32 grazing lactating mares into four groups: no supplement, 15 g, 30 g, or 45 g per day. The 30 g group produced more milk, milk fat ran higher across all supplemented groups, foals weighed more, and muscle-stress blood markers dropped sharply. The sweet spot was 30 g/day — more wasn't better.
Bottom line: Ask your nutritionist about amino-acid support for lactating mares. And hair-test the dam before breeding to know what she's already short on.
Ma et al., 2026. BMC Veterinary Research. DOI: 10.1186/s12917-026-05534-4
+ Breeding Sidebar
+16% Embryo Recovery From a Daily Nutrient Mix
A Brazilian crossover trial ran 12 donor mares across two seasons. Half their normal diet, half their normal diet plus a 40 g/day mixed nutrient supplement (amino acids, vitamins, trace minerals).
The supplemented group hit 81.7% embryo recovery vs. 65.4% control — a +16-point swing. No magic. Just covering the nutritional gaps the base diet was leaving.
Bottom line: Plan supplementation 150 days out, not 15. Know your mare's mineral baseline before you start.
Camargo et al., 2026. J Equine Vet Sci. DOI: 10.1016/j.jevs.2026.105844
⚙ The Cover Story · Diagnostics
Hair vs. Blood vs. Forage: The Honest Truth
We get this question every week. Here's the answer, straight from working horsemen.
Each test does a different job. Anyone telling you one replaces the others is selling you something.
Forage testing — what's going in
Lab analysis of your hay or pasture. Tells you what minerals are available before your horse eats them. Best for: matching a base diet to your forage. Limit: doesn't tell you what your horse absorbs.
Blood testing — the moment in time
Vet draws blood, lab runs it. Reflects what's in circulation today — last 24-48 hours. Best for: acute issues, suspected toxicity, sick horse workups. Limit: the body buffers blood levels tight, so chronic shortages often look "normal."
Hair mineral analysis — the 90-day record
A hair sample shows what was deposited in the strand over the past ~90 days. Best for: chronic problems, heavy-metal screening, tracking patterns over time. Limit: not a diagnostic test on its own — it's a 90-day mineral story.
Real talk. Hair testing labs vary. A 2022 study found 10–58% variance across commercial labs. That's why Mane Metrics uses ICP-MS — the same lab method used in human and pharma diagnostics — and why we publish our methods. Ask any lab what method they run. If they won't say, walk.
Bottom line: Forage tells what's going in. Blood shows today. Hair shows the 90-day record and the heavy metals. They answer different questions. Use them together.
⚠ Toxin Watch · Aluminum
The Aluminum Problem Nobody's Talking About
Aluminum shows up everywhere — soil, water, fertilizer runoff, feed buckets, even some supplements. Your horse encounters it every day. The body tries to clear it. Sometimes it can't keep up.
High aluminum competes with the calcium, magnesium, and phosphorus your horse needs for bones, muscles, and nerves. The classic pattern we see in hair: elevated aluminum paired with mineral imbalances and vague symptoms — poor performance, behavioral changes, slow recovery, a coat that won't shine no matter what you feed.
Routine blood panels rarely catch it. Aluminum doesn't sit in blood long; it parks in tissue. Hair shows the buildup.
Bottom line: If your horse has unexplained chronic issues and a clean bloodwork report, screen for heavy metals. Aluminum is the most common one we flag.
⛬ Gut Health
Hindgut 101: Why the Bacteria Matter More Than the Feed
A horse's hindgut is a fermentation tank. Trillions of bacteria break down fiber and turn it into energy, vitamins, and short-chain fatty acids. Mess with that population and everything downstream changes.
A 2026 study tested how fiber-based feeds shifted the gut bacteria mix. Two things stood out: different fibers grew different bacterial populations, and adding a fiber-based feed didn't hurt the existing good bacteria — a win for owners trying to add calories without wrecking the gut.
The industry has spent years adding more starch — sweet feeds, high-sugar mixes. The hindgut wasn't built for that. Starch overloads the small intestine, dumps undigested sugar into the hindgut, and feeds the wrong bacteria. Result: a horse that won't eat, ulcers, hot temperament, tying up.
Fiber-based feeds — beet pulp, soaked hay cubes, fiber pellets — keep the hindgut happy.
Bottom line: Build calories from fiber first. Use grain only for the energy fiber can't provide. Your horse's gut bacteria will thank you.
Hart et al., 2026. J Equine Vet Sci. DOI: 10.1016/j.jevs.2026.105862
▣ Tech & Tools
Don't Trust ChatGPT With Your Horse (Yet)
A new Colorado State study pitted three AI tools — ChatGPT, Microsoft Copilot, and an extension-service chatbot — against 40 horse-related questions across care, nutrition, genetics, and reproduction.
The results: ChatGPT and Copilot outperformed the extension bot on accuracy. All three struggled with advanced or complex questions. AI tools fell short of what trained equine extension specialists could provide. Performance was uneven across topics.
Translation. AI is fine as a general question — "what's a normal heart rate at rest?" — but it's a bad place to make medical or supplementation decisions for a real horse. AI doesn't know your horse's history, your hay quality, or your local soil.
Bottom line: Use AI like a librarian. Use your vet, your trainer, and your test results like a doctor.
Aldworth-Yang et al., 2026. J Equine Vet Sci. DOI: 10.1016/j.jevs.2026.105924
☀ Seasonal · Spring Pasture
What's Actually Growing in Your Pasture This May
Cool nights and sunny days build up sugar in grass. Horses with insulin issues, EMS, or laminitis history can crash hard.
The traps
Fast weight gain. A horse on lush pasture can gain 50 lbs in a month. If your horse is already running heavy, this is the wrong time to free-feed grass.
Mineral shifts. Young, fast-growing grass runs high in potassium and low in magnesium. That ratio drives nervousness and muscle tightness. Worth knowing if your spring horse suddenly seems "hot."
What to do
Watch body condition weekly · use a grazing muzzle for at-risk horses · test before the new cutting comes in · consider hair testing mid-spring to catch shifts early.
Bottom line: Spring grass is a gift and a threat. Manage it on purpose.
? Reader Q&A
"Lethargic, Dull Coat — But Clean Bloodwork"
Q. My 9-year-old gelding has been dull and tired for months. Losing coat shine. Hasn't changed feed. Vet ran a full blood panel — everything came back normal. What am I missing?
A. You're describing one of the most common patterns we see. Worried owner. Clean bloodwork. A horse that isn't right.
Here's what's likely going on:
He may be low on copper, zinc, or selenium — blood doesn't always show it. The body fights to keep these stable while tissue stores run dry.
He may carry a heavy metal burden — usually aluminum or iron. Both compete with essential minerals. Rarely flagged on routine blood panels.
His mineral ratios may be off. A horse can have "normal" zinc and "normal" copper but a bad Zn:Cu ratio. The ratio matters more than the single numbers for coat, immunity, and behavior.
Run a hair test. The 90-day record shows mineral patterns. Take the results to your vet, build a plan, and re-test in six months.
Ready to find out what your horse is missing?
The Mane Metrics Hair & Mineral Analysis Test Kit measures 42+ elements, critical mineral ratios, and 8 toxic heavy metals. Lab-grade ICP-MS. Plain-English report. Phone consultation included.