{"id":1093,"date":"2026-06-04T07:00:51","date_gmt":"2026-06-04T07:00:51","guid":{"rendered":"https:\/\/foragebaler.com\/?p=1093"},"modified":"2026-06-04T07:00:51","modified_gmt":"2026-06-04T07:00:51","slug":"hay-breeding-mares-pre-foaling-nutrition-low-potassium-guide","status":"publish","type":"post","link":"https:\/\/foragebaler.com\/tr\/hay-breeding-mares-pre-foaling-nutrition-low-potassium-guide\/","title":{"rendered":"\u00dcreme ama\u00e7l\u0131 k\u0131sraklar i\u00e7in saman: Do\u011fum \u00f6ncesi beslenme ve g\u00fcvenlik"},"content":{"rendered":"
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<\/div>\n
Equine Reproduction \u2014 Pre-Foaling Hay Nutrition and Safety<\/span><\/p>\n

\u00dcreme ama\u00e7l\u0131 k\u0131sraklar i\u00e7in saman: Do\u011fum \u00f6ncesi beslenme ve g\u00fcvenlik<\/h1>\n

The hay a mare eats in the last 90 days before foaling determines colostrum quality, retained placenta risk, and whether she produces milk. Two factors dominate: potassium must stay below 1.5% DM in the final 30 days \u2014 a threshold most alfalfa hay exceeds \u2014 and fescue must be withdrawn 60\u201390 days before foaling. This guide covers the K-Ca mechanism, the species traffic light by trimester, and how to test and produce low-K hay for the broodmare market.<\/p>\n

See Species Safety Guide<\/a><\/p>\n<\/div>\n<\/div>\n

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Why the Last 90 Days Change Everything in Mare Hay Management<\/h2>\n

Through most of a mare’s 11-month gestation, hay management follows the same general principles as any mature horse at light work \u2014 adequate protein, reasonable forage quality, and balanced minerals. The last 90 days before foaling are fundamentally different. The fetal growth curve is not linear: approximately 65\u201370% of the foal’s total birth weight accumulates in the final trimester, creating a period of exponentially rising nutritional demand. Simultaneously, the mare’s endocrine system is preparing for parturition, colostrum production, and lactation in a process that is acutely sensitive to dietary cation balance \u2014 specifically, the ratio of potassium to other minerals in the diet. Getting hay selection wrong in this period does not produce a minor quality difference; it can produce a mare with no milk, a retained placenta requiring emergency veterinary intervention, or a foal with inadequate passive immunity.<\/p>\n

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$800\u2013$2,500<\/div>\n
Typical veterinary cost for treating a retained placenta with associated endometritis and laminitis complications in a mare \u2014 a complication that is significantly more common in mares fed ergovaline-containing fescue hay or high-potassium hay in the final trimester<\/div>\n<\/div>\n
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<1.5%<\/div>\n
Target dietary potassium (K) as a percentage of diet DM in the last 30 days before expected foaling \u2014 a threshold that most pure alfalfa hay exceeds (alfalfa typically 1.8\u20132.8% K), making it important to test and manage K from hay in the late gestation period<\/div>\n<\/div>\n
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60-90 g\u00fcn<\/div>\n
Minimum withdrawal period required from all tall fescue hay and pasture before the expected foaling date to eliminate the ergovaline-prolactin suppression effect that causes agalactia, retained placenta, and weak foal syndrome<\/div>\n<\/div>\n<\/div>\n
This article provides nutritional information for hay management decisions \u2014 it does not replace veterinary and equine nutritionist guidance.<\/strong> Pre-foaling mare nutrition is highly individual: a mare’s history, body condition score, current diet composition, health status, and foaling date all affect the specific recommendations appropriate for her. The principles and thresholds in this guide represent current best practices from equine nutrition research literature, but the specific management plan for any broodmare should be developed in consultation with a veterinarian or equine nutritionist who knows the individual animal.<\/div>\n<\/div>\n
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The Potassium Problem: Why High-K Hay Is Dangerous Close to Foaling<\/h2>\n

\"round<\/p>\n

The connection between dietary potassium and pre-foaling hypocalcemia (low blood calcium) in mares is one of the most practically important and least widely understood concepts in equine pre-foaling nutrition. The mechanism involves the DCAD \u2014 dietary cation-anion difference \u2014 which quantifies the balance between positively charged dietary minerals (primarily sodium, potassium) and negatively charged minerals (primarily chloride, sulfur). When the DCAD is strongly positive (high potassium and sodium relative to chloride and sulfur), the body’s acid-base regulatory system responds in ways that impair the hormonal mobilization of calcium from bones during the critical pre-foaling period.<\/p>\n

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The mechanism \u2014 why high K suppresses calcium mobilization<\/div>\n

In the days before foaling, the mare’s parathyroid hormone (PTH) must trigger release of calcium from bone reserves to supply the enormous calcium demand of colostrum production. A strongly positive DCAD (from high-K hay) shifts the body slightly toward metabolic alkalosis \u2014 an alkaline state that blunts the tissue response to PTH. Calcium receptors respond less efficiently to the PTH signal, and the mare cannot mobilize her bone calcium reserves at the rate colostrum demands. The result: blood calcium drops (hypocalcemia), muscle weakness develops, colostrum calcium concentration falls, and in severe cases the mare cannot stand or nurse the foal. The same mechanism causes “grass tetany” in cattle consuming high-K spring grass, and “milk fever” in high-producing dairy cows \u2014 the equine version is less frequently recognized but clinically significant in broodmares.<\/p>\n<\/div>\n

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Potassium content of common hay types<\/div>\n
Alfalfa hay:<\/strong> 1.8\u20132.8% K \u2014 typically exceeds<\/em> the 1.5% target when fed as sole hay
\nRed clover hay:<\/strong> 2.0\u20133.0% K \u2014 very high; avoid in late gestation
\nOrchardgrass hay:<\/strong> 1.0\u20132.0% K (highly variable; test specific lot)
\nTimothy hay:<\/strong> 0.8\u20131.5% K \u2014 usually within or near target
\nTeff grass hay:<\/strong> 0.8\u20131.4% K \u2014 consistently low; excellent choice
\nBermudagrass hay:<\/strong> 0.9\u20131.8% K (variable; test)
\nNative grass hay:<\/strong> 0.6\u20131.2% K \u2014 typically low
\nAlfalfa-grass 50\/50 mix:<\/strong> 1.3\u20132.0% K \u2014 test specific lot<\/div>\n<\/div>\n<\/div>\n
The anionic supplement option:<\/strong> When low-K hay is not available for the last 30 days before foaling, anionic salts (ammonium chloride, calcium chloride, magnesium sulfate) can be added to the diet to shift the DCAD toward negative \u2014 partially offsetting the alkalosis-promoting effect of high-K hay. This is used routinely in pre-calving dairy cow programs and is increasingly used by equine nutritionists in Thoroughbred and performance horse breeding programs. Palatability is the primary management challenge: anionic salts are bitter and mares often reduce intake when they are added to feed. If you are considering anionic supplementation for a mare on high-K hay, consult with an equine nutritionist or veterinarian for appropriate dosing and palatability management \u2014 incorrect dosing produces metabolic acidosis, which is as harmful as the alkalosis it is intended to prevent.<\/div>\n<\/div>\n
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Fescue Hay and Pregnant Mares: A Non-Negotiable Withdrawal Requirement<\/h2>\n

Tall fescue hay from stands infected with the toxic endophyte (Epichlo\u00eb coenophiala<\/em>) is one of the most well-documented reproductive hazards in equine management. The ergovaline produced by the endophyte suppresses prolactin \u2014 the hormone that triggers milk production, colostrum secretion, and several processes involved in normal parturition. The consequences for mares fed toxic fescue in late gestation are clinically serious and frequently require emergency veterinary intervention. University of Kentucky and other equine research programs have documented these outcomes consistently across multiple study populations.<\/p>\n

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AGALACTIA
\nNo milk<\/span><\/div>\n
Complete or near-complete failure to produce colostrum or milk at foaling.<\/strong> Ergovaline suppresses prolactin production \u2014 the hormone that signals the mammary gland to initiate milk and colostrum secretion. A foal born to an agalactic mare receives inadequate immunoglobulins (IgG) from colostrum, leaving it vulnerable to septicemia, respiratory infections, and other neonatal conditions. Emergency response: colostrum from a donor mare or commercial equine colostrum bank must be administered within the first 6\u201312 hours of life. Cost of emergency colostrum sourcing: $150\u2013$400 in most regions.<\/div>\n<\/div>\n
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RETAINED PLACENTA<\/div>\n
Failure of the placenta to be expelled within 3 hours of foaling.<\/strong> Research from University of Kentucky documented retained placenta rates of 35\u201350% in mares on toxic fescue versus 2\u20135% in control mares on clean forage. Retained placenta leads to endometritis (uterine infection), systemic toxemia, and \u2014 as a secondary consequence \u2014 laminitis from endotoxin absorption. This is a veterinary emergency requiring oxytocin treatment, manual extraction assistance, systemic antibiotics, and anti-inflammatory medication. Total treatment cost: $500\u2013$1,500 minimum.<\/div>\n<\/div>\n
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PROLONGED GESTATION<\/div>\n
Gestation extended 10\u201320+ days beyond normal (320\u2013360 days).<\/strong> Post-mature foals from prolonged gestation are often oversized and physically immature (paradoxically) \u2014 with reduced joint flexibility, poor suckle reflex, and neurological immaturity (weak foal syndrome). The extended gestation also significantly increases the probability of dystocia requiring obstetric intervention.<\/div>\n<\/div>\n<\/div>\n
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The 60\u201390 day withdrawal rule \u2014 why timing matters<\/div>\n

Ergovaline’s effect on prolactin is not immediate \u2014 it accumulates over weeks of exposure and clears slowly after the source is removed. Removing a mare from fescue hay 60 days before the expected foaling date provides adequate time for ergovaline to clear from the system and prolactin levels to normalize before colostrum production begins. Most equine veterinary specialists recommend 90 days as a more conservative margin for mares with a history of fescue-related problems, mares over 15 years old, or mares in their first foaling. The withdrawal applies to both fescue hay AND fescue pasture \u2014 both sources deliver ergovaline at significant concentrations.<\/p>\n<\/div>\n

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Novel endophyte fescue \u2014 cautious approach recommended<\/div>\n

Novel endophyte fescue varieties (MaxQ and others) produce no ergovaline and have not been shown to cause the classic reproductive complications associated with toxic endophyte fescue in controlled studies. However, most equine veterinary specialists recommend maintaining a 60-day withdrawal from all fescue hay \u2014 including novel endophyte varieties \u2014 as a precautionary measure close to foaling. The reasoning: the reproductive stakes are high, the withdrawal has no cost in a hay that has clean alternatives, and the margin of confidence in any novel endophyte-derived hay recommendation is not absolute. Consult your veterinarian for guidance specific to your mares’ history and your hay supply situation.<\/p>\n<\/div>\n<\/div>\n<\/div>\n

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Hay Species Safety by Trimester: The Traffic Light Guide<\/h2>\n

Not all hay recommendations for mares are static across the full 11-month gestation. The K concern is primarily a late-gestation issue; fescue must be avoided throughout; certain legume-quality advantages apply more in early gestation than late. This trimester-organized guide gives specific guidance for each of the most commonly available hay species.<\/p>\n

\n\n\n\n\n\n\n\n\n\n\n\n\n
Hay species<\/th>\nEarly\u2013Mid gestation
\nMonths 1\u20137<\/span><\/th>\n		Late gestation
\nMonths 8\u201310<\/span><\/th>\n		Last 30 days
\nPre-foaling<\/span><\/th>\n		Lactation
\nPost-foaling<\/span><\/th>\n<\/tr>\n<\/thead>\n
Timothy hay<\/td>\n\u2713 SAFE<\/td>\n\u2713 SAFE<\/td>\n\u2713 SAFE (test K)<\/td>\n\u2713 SAFE<\/td>\n<\/tr>\n
Teff grass hay<\/td>\n\u2713 SAFE<\/td>\n\u2713 SAFE<\/td>\n\u2713 PREFERRED<\/td>\n\u2713 SAFE<\/td>\n<\/tr>\n
Bermudagrass hay<\/td>\n\u2713 SAFE<\/td>\n\u2713 SAFE<\/td>\n\u26a0 TEST K<\/td>\n\u2713 SAFE<\/td>\n<\/tr>\n
Orchardgrass hay<\/td>\n\u2713 SAFE<\/td>\n\u2713 SAFE<\/td>\n\u26a0 MUST TEST K<\/td>\n\u2713 SAFE<\/td>\n<\/tr>\n
Alfalfa hay<\/td>\n\u2713 SAFE<\/td>\n\u26a0 MONITOR K<\/td>\n\u26a0 TEST \u2014 limit or blend<\/td>\n\u2713 EXCELLENT<\/td>\n<\/tr>\n
Native grass hay<\/td>\n\u2713 SAFE<\/td>\n\u2713 SAFE<\/td>\n\u2713 SAFE<\/td>\n\u26a0 Supplement protein<\/td>\n<\/tr>\n
Red clover hay<\/td>\n\u26a0 CAUTION (slaframine)<\/td>\n\u2717 AVOID (high K)<\/td>\n\u2717 AVOID<\/td>\n\u26a0 Limited use<\/td>\n<\/tr>\n
Toxic fescue (KY-31)<\/td>\n\u2717 AVOID all gestation<\/td>\n\u2717 AVOID<\/td>\n\u2717 ABSOLUTELY NOT<\/td>\n\u2717 AVOID (affects milk)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\n
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Alfalfa in Late Gestation: The Practical Balance<\/h2>\n

\"round<\/p>\n

The alfalfa-in-late-gestation question creates genuine uncertainty among mare owners and hay producers because the answer is nuanced. Alfalfa is an excellent mare hay in most of gestation and an excellent lactation hay \u2014 its calcium content (1.2\u20132.0%) supports the mare’s bone calcium mobilization and colostrum production, and its protein (18\u201324% CP) supports fetal growth. The specific concern is the potassium content and the last 30 days before foaling, when the DCAD effect on calcium mobilization is most critical.<\/p>\n

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The practical resolution by phase<\/div>\n
Months 1\u20137 (early\/mid gestation):<\/strong> Alfalfa is appropriate as a primary or partial hay source. No K concern at this stage. CP and Ca support early fetal development.
\nMonths 8\u201310 (late gestation):<\/strong> Transition from pure alfalfa to a 50\/50 alfalfa-grass mix. A well-managed blend typically tests 1.3\u20131.8% K \u2014 within or near the acceptable range. Test the specific mix’s K before relying on it.
\nLast 30 days (pre-foaling):<\/strong> Pure grass hay (timothy, teff, tested low-K orchardgrass) is preferable if available. If the alfalfa-grass blend tests below 1.5% K, it can continue under veterinary guidance. Pure alfalfa at 2.0\u20132.8% K is generally not recommended as the sole hay for the final 30 days.<\/div>\n<\/div>\n
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Alfalfa post-foaling: excellent choice<\/div>\n

Once the mare has foaled, the K restriction concern diminishes significantly. The lactating mare’s tremendous energy and calcium requirements make alfalfa an excellent hay choice post-foaling \u2014 its high CP supports milk protein, its high calcium supports the 4\u20136 g of calcium per liter of milk the mare produces, and its high energy density helps the mare maintain body condition through the lactation period. Operations that keep mares on grass hay post-foaling for extended periods often see lactating mares lose condition because they cannot consume sufficient grass hay to meet the caloric demands of peak milk production. Transitioning back to alfalfa-grass mix or pure alfalfa within the first week post-foaling is appropriate management for most broodmares.<\/p>\n<\/div>\n<\/div>\n<\/div>\n

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Forage Testing for Mare Nutrition: What to Order and When<\/h2>\n

The standard forage test ordered for cattle hay \u2014 CP, ADF, NDF, TDN \u2014 is insufficient for broodmare hay management because it does not include the mineral values that determine late-gestation hay safety. Potassium must be specifically requested; it is not included in any standard panel offered by NFTA-certified laboratories. The additional mineral tests add approximately $15\u2013$25 to a standard panel and provide information that is essential for the last-90-days management period.<\/p>\n

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Minimum panel for broodmare hay<\/div>\n