Horse Breeding Documentation: What to Record at Every Stage (2026 Guide)

By Brian Bickell, who raises paint and quarter horses at Bickell Ranches in Stillwater, Oklahoma. Breeding season taught him more about record-keeping than any software project ever did.

Breeding horses generates more paperwork per horse than anything else in equine management. Heat cycle tracking, ultrasound findings, breeding dates, semen evaluations, pregnancy checks, foaling records, stallion contracts, and registry filings — the documentation starts months before conception and doesn't stop until the foal is registered.

Miss a detail, and it can cost you. A forgotten stallion breeding report means your foal can't be registered. An unrecorded post-breeding ultrasound means fluid accumulation goes untreated and the mare loses the pregnancy. A lost service contract means no recourse when the live foal guarantee is disputed.

Educational, not veterinary or legal advice. Reproductive management belongs to your vet, and contracts belong to an attorney. This guide is a record-keeping framework to help you capture what they'll need.

In This Guide

• Mare Heat Cycle Tracking
• Veterinary Reproductive Records
• Pregnancy Monitoring
• Stallion Records
• Contracts and Legal Documents
• Registry-Specific Breeding Rules

Mare Heat Cycle Tracking

The mare's estrous cycle averages 21 days: 5–7 days of estrus (receptive to breeding) followed by 14–16 days of diestrus. Ovulation typically occurs 24–48 hours before the end of behavioral estrus.

Teasing Scores

Daily teasing with a teaser stallion or gelding is the primary way to track a mare's cycle. Use a standardized scoring system:

Score	Behavior
0	Hostile — ears pinned, kicks, strikes
1	Indifferent — no interest
2	Mild interest — approaches but no posturing
3	Moderate — winking, urination, tail raising intermittent
4	Strong estrus — consistent winking, squatting, tail raised and deflected
5	Peak standing heat — fully receptive, leaning into teaser

Record scores daily during breeding season (February through July for most registries). A mare progressing from 0 → 3 → 5 over several days is approaching ovulation. Irregular cycles, split heats, or prolonged estrus (more than 10 days) should be flagged for veterinary evaluation.

Transitional Heat

The most common source of early-season frustration. As mares emerge from winter anestrus in spring, they produce irregular, prolonged estrus — sometimes 20+ days — with follicles that grow and regress without ovulating. Don't breed during transitional heat. Wait for the first true ovulation of the season.

Lights-under-management can advance the first ovulation by 6–8 weeks: 16 hours of light (natural + artificial, minimum 200 lux at eye level) starting December 1. Track the start date and confirm response by ultrasound in early February.

Veterinary Reproductive Records

Ultrasound Findings

Reproductive ultrasounds track ovarian and uterine status throughout the cycle. For each exam, record:

• Date and time
• Follicle size per ovary (in millimeters — ovulation typically occurs at 35–45mm)
• Uterine edema score (graded 0–4, indicating estrogen influence)
• Uterine fluid (presence, volume, echogenicity)
• Cervix tone
• Veterinarian's breeding recommendation

Daily ultrasound typically begins when the dominant follicle reaches 30mm. The vet is watching for the right moment to breed — and a complete record of prior cycles helps predict this mare's individual pattern.

Breeding Event Records

For each breeding, document:

• Date and time
• Method: live cover, AI fresh, AI cooled/transported, AI frozen
• Stallion identification (registered name, registration number, owner)
• Semen quality at insemination (for AI): progressive motility, concentration, total motile sperm count
• Pre-ovulation follicle size
• Ovulation induction agent if used (hCG or deslorelin — date and time administered)
• Ovulation confirmation via ultrasound (date and time)
• Post-breeding uterine fluid check at 6–12 hours and again at 24 hours

That last item, the post-breeding fluid check, prevents more early pregnancy losses than almost anything else you can do. Mares that pool fluid ("dirty mares") need uterine lavage and oxytocin. Document the treatment given and follow-up findings.

Tip: HorseBook tracks breeding records with dates, methods, and semen evaluations linked to specific stallions — all under one mare's profile. No spreadsheet tabs, no Post-it notes on the barn fridge.

Pregnancy Monitoring

The Pregnancy Check Timeline

Check	Timing	Purpose
First	Day 14–16	Confirm embryonic vesicle, check for twins
Second	Day 25–30	Heartbeat visible (~120 bpm confirms viability)
Third	Day 45	Confirm continued development
Fourth	Day 60–70	Optional fetal sexing (95%+ accuracy at 60–65 days)
Late	5 and 9 months	Wellness checks, fetal positioning

Twin management is critical. Unmanaged twins have approximately a 90% chance of losing both foals. Twin reduction is performed at the day 14–16 check by manual crush of one vesicle. Record which vesicle was reduced and the follow-up confirmation.

The day 36–38 threshold: After this point, endometrial cups have formed and produce eCG (equine chorionic gonadotropin) for months. If the pregnancy is lost after cup formation, the mare won't cycle back that season. This is a significant planning consideration.

Gestation Tracking

Average gestation is 340 days, with a normal range of 320–370 days. Critical records to maintain:

• Last breeding date (for expected foaling date calculation)
• Individual mare gestation history — mares are remarkably consistent across pregnancies, typically within 5–7 days of their personal average. A mare who consistently foals at day 335 going to day 350 is abnormal for her, even though 350 is within the population range.
• Pre-foaling signs: udder development timeline, waxing of teats (typically 24–48 hours before foaling), and milk calcium levels (>200 ppm on a commercial test strongly predicts foaling within 24–48 hours)

Pregnant Mare Vaccinations

Don't forget the vaccination schedule during pregnancy. Killed EHV vaccine (Pneumabort-K or equivalent) at months 3, 5, 7, and 9 of gestation. Core vaccine boosters 4–6 weeks before foaling for maximum colostral antibody transfer. See our vaccination guide for the full pregnant mare protocol.

Stallion Records

Stallion Breeding Reports

Most registries require an annual report listing every mare bred. AQHA requires this filed by December 31 of the breeding year. The report includes mare name, registration number, breeding dates, and method.

This is non-negotiable. If the stallion breeding report isn't filed, foals from those matings cannot be registered, regardless of what the mare owner does on their end. See our breed registration guide for registry-specific deadlines and requirements.

The stallion owner also issues a stallion service certificate (breeder's certificate) to each mare owner, which the mare owner needs for foal registration.

Semen Evaluation Records

For each collection, record:

• Date and time
• Gel-free volume (ml)
• Concentration (sperm per ml)
• Progressive motility (percentage)
• Total sperm count (volume × concentration)
• Morphology (percentage of normal cells, if evaluated)
• Number of doses produced

Standard AI dose targets: 500 million progressively motile sperm for cooled shipped semen; 200–800 million total for frozen (varies by stallion).

Shipped Semen Records

Document: shipment date, recipient (mare owner and veterinarian), carrier and tracking number, container type (Equitainer or similar), number of doses, and insemination instructions. The receiving vet should document post-arrival motility before insemination.

Contracts and Legal Documents

Stallion Service Contracts

Every breeding should be governed by a written contract. It should specify:

• Stud fee and payment schedule
• Live foal guarantee definition — the industry standard is "stands and nurses for 24–48 hours"
• Rebreed provisions if the mare doesn't conceive or the foal doesn't survive (most contracts allow one rebreed the following season)
• Booking fee (typically non-refundable)
• Collection and shipping fees (usually separate from the stud fee)
• Mare care board if the mare is sent to the stallion's facility
• Contract year limitations

Mare Lease Agreements

When leasing a mare for breeding, the agreement should cover: lease term, who pays breeding and veterinary costs, ownership of the resulting foal, insurance requirements, and return condition of the mare.

Embryo Transfer Agreements

Specify: ownership of embryos, number of transfer attempts, costs for recipient mare care, disposition of embryos if the contract terminates, and who handles registration paperwork.

Registry-Specific Breeding Rules

Know your registry's rules before planning a breeding:

• AQHA: AI (fresh, cooled, frozen) all permitted. Embryo transfer permitted with prior enrollment. One registered foal per mare per year (standard), or unlimited via the multiple embryo program.
• Jockey Club: Live cover only. No AI of any kind. No embryo transfer. No exceptions. This is the most restrictive breeding rule in the industry.
• APHA: AI permitted. Embryo transfer allowed with prior approval.
• ApHC: AI and embryo transfer permitted. Accepts crosses with AQHA, APHA, Jockey Club, and Arabian horses.
• AHA: AI and embryo transfer permitted. Purebred offspring require both parents to be registered Arabians.

For a detailed side-by-side comparison of all major registries — including fees, deadlines, and transfer processes — see our breed registration guide.

Keeping It All Together

Breeding generates more records per horse than any other part of horse ownership. A single mare in a single breeding season generates ultrasound reports, teasing logs, breeding records, pregnancy checks, vaccination records, and — if everything goes well — foaling details, neonatal records, and registration paperwork.

In HorseBook, all of this lives under one horse's profile: breeding records with dates and methods, semen evaluations linked to specific stallions, and foaling records with the details your registry needs for registration. No binder shuffling, no spreadsheet tabs, no Post-it notes on the barn fridge.

For a detailed guide on the foaling process — from pre-foaling signs through neonatal care and IgG testing — see our foaling records and mare tracking guide.

The records you keep during breeding aren't just for this season. They're the foundation for next year's decisions — which stallions produced, which mares conceived easily, which needed extra management. That data is only useful if you can find it.

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Brian Bickell is the founder of HorseBook and raises paint and quarter horses at Bickell Ranches in Stillwater, Oklahoma.