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📊 Interactive Calculators
Free ToolsGestation Calculator
Due date, milestones & countdown from breeding date
Average horse gestation: 340 days (range 320–370). Standardbreds average 335–342 days. Mares bred earlier in the year tend to have longer gestations.
Horse Age Calculator
Current age in years/months plus human equivalent
Body Weight Estimator
Henneke formula — heart girth + body length → weight in lbs
Measure heart girth: tape around barrel just behind front legs. Body length: point of shoulder to point of buttock. Use a soft flexible tape.
Feed Calculator
Daily hay, grain & water by weight + activity level
Stud Fee ROI Calculator
Total investment, expected profit & ROI %
📋 Reference Guides
Quick ReferenceBase colors determined by two loci: Extension (E) and Agouti (A). All other colors are modifications of these three bases.
Cr = Cream dilute gene. Dun = dun dilute gene (primitive markings). Rn = Roan (can be lethal homozygous in some breeds). G = Gray (progressive depigmentation). Use the MatchSire simulator for full probability calculations.
| Disease | Inheritance | Affected Breeds | Test Available |
|---|---|---|---|
| HYPP (Hyperkalemic Periodic Paralysis) | Autosomal Dominant | Quarter Horse, Paint, Appaloosa | Yes — UC Davis VGL |
| GBED (Glycogen Branching Enzyme Deficiency) | Autosomal Recessive | Quarter Horse, Paint | Yes — UC Davis VGL |
| HERDA (Hereditary Equine Regional Dermal Asthenia) | Autosomal Recessive | Quarter Horse (cutting lines) | Yes — UC Davis VGL |
| OLWS (Overo Lethal White Syndrome) | Autosomal Recessive | Paint, Pinto | Yes — Frame Overo gene |
| MH (Malignant Hyperthermia) | Autosomal Dominant | Quarter Horse, Paint, Appaloosa | Yes — UC Davis VGL |
| PSSM (Polysaccharide Storage Myopathy) | Autosomal Dominant (PSSM1) | Draft, Quarter Horse, Warmblood | Yes — UC Davis, Etalon |
| SCID (Severe Combined Immunodeficiency) | Autosomal Recessive | Arabian | Yes — multiple labs |
| CSNB (Congenital Stationary Night Blindness) | X-linked | Appaloosa | Yes — linked to LP gene |
| JEB (Junctional Epidermolysis Bullosa) | Autosomal Recessive | Belgian Draft, American Saddlebred | Yes — COL17A1 mutation |
| DMRT3 (Gait Gene) | Autosomal Recessive (C/C = trot/pace capable) | All gaited breeds, Standardbred | Yes — UC Davis, Etalon |
Test carriers before breeding. N/N = clear, N/Af = carrier, Af/Af = affected. Carriers for recessive diseases show no symptoms but can produce affected foals when bred to other carriers.
| Vaccine | Type | Frequency | Notes |
|---|---|---|---|
| Eastern/Western Equine Encephalomyelitis (EEE/WEE) | Core | Annually (spring) | Booster before mosquito season |
| West Nile Virus (WNV) | Core | Annually (spring) | Some areas: semi-annual |
| Rabies | Core | Annually | USDA-licensed products only |
| Tetanus | Core | Annually | Booster after wounds |
| Equine Herpesvirus (EHV-1/4) | Risk-based | Every 6 months or quarterly if at risk | Pregnant mares: 5, 7, 9 months |
| Equine Influenza | Risk-based | Every 6 months (performance horses: quarterly) | Racing horses: follow state rules |
| Strangles (Streptococcus equi) | Risk-based | Annually or per outbreak risk | Intranasal or IM depending on product |
| Botulism | Risk-based | Annually if at risk | Foals in endemic areas |
| Rotavirus | Risk-based | Pregnant mares: 8, 9, 10 months | Provides passive immunity to foal |
Always consult your veterinarian for location-specific recommendations. Foals require a primary series; timing varies by dam vaccination status. Broodmares: vaccinate 4–6 weeks before foaling.
| Season | Drug Class | Active Ingredient | Targets |
|---|---|---|---|
| Spring (March–April) | Macrocyclic Lactone | Ivermectin or Moxidectin | Strongyles, bots, pinworms, ascarids |
| Summer (June–July) | Benzimidazole | Fenbendazole (5-day larvicidal) | Encysted small strongyles (larval) |
| Fall (October–November) | Macrocyclic Lactone + Praziquantel | Ivermectin + Praziquantel | All strongyles, tapeworms, bots |
| Winter (December–January) | Pyrimidine | Pyrantel pamoate | Large/small strongyles, pinworms, ascarids |
Resistance management: Rotate between drug classes (not just products). Use fecal egg counts (FEC) to identify high shedders — only treat horses with >200–500 EPG. Strategic deworming beats calendar-based rotation.
Foals: treat at 2, 4, 6 months for ascarids (pyrantel or fenbendazole — NOT ivermectin/moxidectin for foal ascarids due to mass die-off risk). Moxidectin: never use in foals under 4 months.
| Score | Description | What to Feel | Action |
|---|---|---|---|
| 1 — Poor | Extremely emaciated | All bone prominences, no fat | 🔴 Emergency vet |
| 2 — Very Thin | Emaciated | Ribs, spine, hip bones easily visible | 🔴 Immediate feeding increase |
| 3 — Thin | Thin | Slight fat cover over ribs, easily felt | 🟡 Increase calories |
| 4 — Moderately Thin | Negative ridge along back | Ribs faintly visible, felt with slight pressure | 🟡 Monitor closely |
| 5 — Moderate ✓ | Ideal — back level | Ribs felt with firm pressure, fat over loin | 🟢 Maintain |
| 6 — Moderately Fleshy | Slight crease down back | Ribs felt with firm pressure, fat beginning to fill | 🟢 Acceptable range |
| 7 — Fleshy | May have fat deposits | Ribs hard to feel, fat deposits on neck, withers | 🟡 Reduce feed |
| 8 — Fat | Crease down back | Ribs not felt, fat deposits on inner buttocks | 🟡 Reduce calories + exercise |
| 9 — Extremely Fat | Obvious crease down back | Patchy fat, flank filled in, obvious crease | 🔴 Vet evaluation, insulin resistance risk |
Ideal BCS for breeding mares: 5–6. Studies show mares at 5–7 have better conception rates. Obese mares (7+) have higher insulin resistance and pregnancy complications. Target BCS 5.5 before breeding season.
| Parameter | Normal Range | Emergency Threshold | Notes |
|---|---|---|---|
| Temperature (rectal) | 99–101°F (37.2–38.3°C) | >102°F or <97°F | Higher post-exercise; AM is lower |
| Heart Rate (pulse) | 28–44 bpm | >60 bpm at rest | Foals: 70–100; elevated by pain/fever |
| Respiratory Rate | 12–20 breaths/min | >30 at rest | Count flank movements for 15 sec × 4 |
| Capillary Refill Time (CRT) | <2 seconds | >3 seconds | Press gum, release, count to pink return |
| Gum Color | Pale pink, moist | White, blue, dark red, tacky | Bright red = toxemia; gray = shock |
| Gut Sounds | Active borborygmi all 4 quadrants | Absent in any quadrant >2 min | Listen with stethoscope or ear to flank |
| Digital Pulse (hooves) | Barely palpable | Bounding, easily felt | Bounding = laminitis or hoof abscess |
| Hydration (skin tent test) | Returns in <1 second | Stays tented >2 seconds | Pinch neck skin, time to flatten |
Know YOUR horse's baseline. Take normal vitals on a calm day and record them. Variations mean more when you have a reference point. When in doubt, call your vet — early intervention is always better.
| Timeline | What to Do | Why |
|---|---|---|
| 30 days out | Move mare to foaling stall; get her comfortable with it | Reduces stress at foaling time |
| 30 days out | Vaccinate (EHV, Rotavirus booster if applicable) | Maximize colostrum antibody levels |
| 30 days out | Deworm with ivermectin + praziquantel | Reduces parasite transfer to foal |
| 2–3 weeks out | Prepare foaling kit (see below) | You won't have time when labor starts |
| 2 weeks out | Watch for wax on teats (waxy pre-milk) | Sign of imminent foaling (24–72 hrs) |
| 1 week out | Check colostrum quality if possible (Brix refractometer) | Poor quality = foal needs supplement |
| Days before | Test milk calcium (>200 ppm = foaling imminent) | More reliable than waxing alone |
| At foaling | Stage 1 (restless, sweating): 1–4 hrs normal | Do not intervene unless >4 hrs |
| At foaling | Stage 2 (water breaks to foal out): 20–30 min | Call vet if no progress at 10 min |
| Post-foaling | Stage 3 (pass placenta): within 3 hours | Retained placenta = emergency at 3 hrs |
| Within 1 hour | Foal should stand and nurse | "1-2-3 rule": 1 hr stand, 2 hrs nurse, 3 hrs vet check |
Foaling Kit Essentials: Clean towels, tail wrap, iodine solution (7% for navel dipping), flashlight, gloves, enema (foal Fleet), Brix refractometer, vet's emergency number, camera/video for documentation.
🔗 Industry Directory
Curated Links📰 Learning Center
Articles & GuidesUnderstanding DMRT3: The Gait Keeper Gene
In 2012, researchers at Uppsala University identified a single gene mutation — DMRT3 — that fundamentally determines a horse's gait capability. A stop codon at position 301 (C/C genotype) is what allows horses to trot, pace, and perform ambling gaits. Horses without this mutation (A/A) can only walk, trot, or canter.
For Standardbred breeders, this is arguably the most important gene in the breed. All competitive trotters and pacers carry at least one copy (N/C or C/C). Homozygous C/C horses may have superior gait consistency — though environmental factors, training, and equipment still play the dominant role in racing performance.
The MatchSire simulator uses DMRT3 data when available in our stallion database, allowing you to assess gait gene inheritance in prospective matings.
Run DMRT3 simulation →How to Read a Genetic Test Report
When you get results back from UC Davis, Etalon, or Animal Genetics, you'll see genotype notation that looks cryptic at first. Here's the key: most tests report two alleles (one from each parent) using locus-specific notation.
N/N = Two normal (wild-type) alleles. Horse is clear and cannot pass the variant to offspring. N/Af = One normal, one variant allele. Horse is a carrier — shows no symptoms for recessive diseases, but can pass the variant. Af/Af = Two variant alleles. Horse is affected (for recessives) or has double dose effect (for dominants).
For coat color, the notation is gene-specific: E/e means heterozygous at Extension (carries both "has pigment" and "red" alleles). Always read the lab's key — notation varies between labs.
Learn more in the simulator →What is COI and Why Does It Matter?
The Coefficient of Inbreeding (COI) measures the probability that both copies of a gene in an individual are identical by descent — inherited from the same ancestral source. A COI of 0% means no common ancestors in the pedigree. A COI of 25% means the equivalent of a full-sibling mating.
Moderate inbreeding (COI 2–5%) is often used to "fix" desirable traits — what breeders call linebreeding. High inbreeding (>12.5%) significantly increases the risk of expressing recessive genetic diseases and reduces reproductive fitness through "inbreeding depression."
The right COI depends on your goals, your breed's existing diversity, and whether you're testing clear of known disease mutations. Standardbred gene pools are already moderately inbred due to founder effects — know your stallion's COI before you breed.
Run a COI check in the simulator →Choosing the Right Stallion: A Breeder's Guide
The stud fee is the last thing you should consider. Before you look at price, evaluate genetic complement: what does your mare carry, and does the stallion's genetic profile fill her gaps? A $5,000 stallion that nicks perfectly with your mare is worth more than a $25,000 name brand that doesn't.
Key factors: (1) Race record — not just wins, but earnings per start and class level. (2) Get-to-race stats — what % of his foals start, and at what rate? (3) Gait gene genotype for Standardbreds. (4) Disease carrier status — always breed tested sire to tested mare. (5) Conformation — look at the get, not just the sire. (6) Nick patterns — has this cross worked historically?
MatchSire's simulator was built to answer exactly these questions. Upload your mare's genetic data and run a simulation against any standing stallion in our database.
Start simulating →Mare Management: From Breeding to Foaling
Mares are seasonally polyestrous — cycling primarily from March through October in the Northern Hemisphere, triggered by increasing daylight. During the "spring transition," cycles are often irregular and anovulatory. Artificial lighting (16 hours) starting December 1st can advance the breeding season by 6–8 weeks — essential for February Standardbred registrations.
Heat detection: mares show estrus for 4–7 days, ovulating 24–48 hours before the end of behavioral heat. Breeding timing for AI: inseminate within 6 hours of ovulation for fresh chilled semen, within 12 hours for live cover. Frozen semen: breed within 2–4 hours of ovulation — requires careful monitoring with rectal palpation or ultrasound.
Post-breeding: confirm pregnancy at 14–16 days by ultrasound, check for twins (immediate intervention needed), and monitor at 25–28 days for heartbeat. Good records from breeding forward give you the data you need when foaling day arrives.
Breeding season calendar above →