Lecture 19 - 20
Introduction to Thoroughbred Foal Production
Achieving a thoroughbred (TB) foal per year involves overcoming several formidable hurdles:
Horses are classified as seasonal (long day) breeders.
Mares have a gestation period of approximately 11 months.
The birth of twins is not permitted within thoroughbred breeding.
Limited access to stallions can pose a challenge.
Timing of Breeding
Thoroughbred birthday is set on 1st August (Standardbred: 1st September).
Foals born between August and October are more mature compared to those born later, influencing their performance as two-year-olds.
To maximise maturity advantage, the breeding season begins on September 1st.
Note: In the Northern Hemisphere, the birthday falls on January 1st.
Oestrus Cycle in Mares
Seasonal Polyoestrus (Long Day Breeders)
Mares that are not in foal (dry) will begin their reproductive cycling as daylight increases with the seasons.
Artificial lighting might be necessary to induce cycling in August and September.
Oestrus Cycle Details:
21-day cycle**:** Oestrus lasts approximately 5 days, with ovulation occurring in the late stage of oestrus.
Lactating Mares: Experience "foal heat" typically occurring 10 days (range: 5-12 days) post-foaling.
Detection of Oestrus in Mares
Behavioural Signs of Oestrus:
The mare seeks the presence of a teaser stallion.
Signs include squealing and vulval "winking."
Increased frequency of urination can also indicate oestrus.
Veterinary Input:
Ultrasonography provides insights into the reproductive tract to assess readiness for breeding.
Mare Readiness for Breeding
Indicators that a mare is ready to breed include:
The presence of an ovulatory follicle (its size varies between individual mares).
Increasing uterine oedema.
Cervix relaxation during oestrus.
Breeding strategy during constrained resources may involve breeding mares every second day until they show non-receptivity.
Optimal Breeding Conditions
Serve the mare when:
Teasing behaviour is positive.
Dominant follicle is larger than 30 mm (grows approximately 5 mm/day).
Uterine oedema is observed (scale of ~2).
Veterinary intervention may include administering ovulation hastening agents.
Causes of Mare Fertility Problems
Desired per cycle fertility rate: 60-85% for TB and TB-type mares.
Common causes of infertility or apparent infertility include:
Embryonic Death: Up to 40 days post mating.
Extrinsic Factors:
Poor management practices or inadequate condition of the mare.
Stallion infertility.
Timing of the breeding season relative to daylight.
Intrinsic Factors:
Age-related issues.
Hormonal and physical abnormalities (e.g. ovarian or uterine issues).
Infectious diseases such as endometritis.
Management of Mare Fertility Issues
Uterine Biopsy:
Distinguishes between infectious and non-infectious endometritis and evaluates breeding prognosis.
Uterine Lavage:
Procedure to clear debris, exudates, and treat infections.
For infectious issues, the causal agent's identification is critical:
Conduct culture and sensitivity testing.
Use antimicrobial therapy as needed.
Caslick Vulvoplasty Procedure:
Involves the closure of the upper vulva to prevent bacteria from entering the reproductive tract.
Stallion Management
Selecting a Stallion:
Key factors include:
Stallion's history (if available).
Temperament and libido.
Age and conformation evaluation.
Full reproductive tract examination and semen evaluation.
Ensure the absence of chromosomal abnormalities and infections.
Stallion Covering Capacity
The top 80 TB stallions in Australia may cover over 100 mares per season (spanning from 1st September to early December).
Some highly sought-after stallions may cover more than 200 mares.
Coverage routine variations include:
One or two covers per day across 6 days with a day of rest.
Two covers daily for 8 days with a follow-up of 2 days’ rest.
Shuttle Stallions:
These stallions move between the Northern and Southern Hemispheres.
General Stallion Management Strategies
Provide individual paddocks to prevent fighting.
Maintain large, airy loose boxes to avoid stress and boredom.
Disease Control Sampling:
Stallions must also be tested alongside mares.
Swab for bacterial infections pre, and perhaps mid-season, targeting areas like the urethra and prepuce.
Test for specific pathogens such as CEM (Taylorella), Klebsiella, and Pseudomonas.
Conduct blood tests for EHV (Equine Herpesvirus) and EAV (Equine Arteritis Virus).
Preparation of Stallions for Mating
Stallions must be in good physical condition (Body Condition Score of 3/5).
Vaccinations recommended for:
Tetanus.
Strangles.
EHV.
EVA.
Mating Management Procedures:
Remove stallion shoes to prevent injury to mares.
Artificial lighting to advance the breeding season is usually not necessary.
Proper hygiene practices at mating include washing the genital area with warm, clean water.
Ensure that the mare is ready and waiting in the designated covering area.
Semen Collection and Evaluation
Semen production levels remain consistent whether stallions are used daily or every other day.
Daily usage might yield lower sperm concentrations per ml but may still be acceptable.
Beware that excessive use can lead to reduced libido, and inadequate use can compromise semen quality.
Collection is typically performed using a dummy mare and artificial vagina.
Semen Evaluation Protocols:
pH: Optimal range is 7.3-7.7.
Motility: Assessed on a warmed microscope slide on a 0-5 scale.
Morphology: Live to dead sperm ratio should be evaluated.
Concentration: Measured using a haemocytometer or automated analyst (target of 30-600 x 10^6/ml).
Bacteriology: Includes leukocyte counts.
Reproduction Efficiency
Natural Breeding Challenges
Natural breeding is the only form of breeding permitted in the Thoroughbred industry.
Advantages of natural breeding include:
More control over breeding services and semen management.
Restrictions include:
Limited number of mares a stallion can serve.
Geographical constraints, especially during disease outbreaks (e.g., EI outbreak in 2007).
Risks include disease transmission and potential injuries.
Artificial Insemination (AI) Benefits
AI is routinely executed for non-thoroughbred breeds, with a key role for veterinarians.
Advantages include:
A single stallion can breed many mares, albeit at the cost of genetic diversity.
Does not require the mare and stallion to be co-located.
Reduces the injury risks for all parties involved (handlers, mares, stallions).
Minimizes disease transmission risks.
Facilitates breeding from challenging mares and stallions.
Defining Reproductive Efficiency
Pregnancy Rate: Understanding this metric is essential as the percentage of mares pregnant at the season's close can be misleading.
Expected per-cycle fertility rate is 60-85% for TB and TB-type mares.
Approximately 70% of TB mares produce a live foal, with potential losses occurring after day 40 post-conception.
Reduced fertility may stem from individual mare or stallion factors (the stallion's effectiveness is determined by the fertility of the mares available).
Optimizing pregnancy rates involves good veterinary input and comprehensive management protocols, including rigorous handling of walk-ins and client-owned mares.
Implications of Reduced Stallion Fertility
Poor per-cycle fertility can lead to:
Fewer mares checking in foal across the breeding season, thus diminishing stud fee revenues.
Foals born later in the foaling season result in younger, smaller two-year-olds who are at a competitive disadvantage.
Lower sales prices for yearlings in auctions.
Return visits required for walk-ins or client-owned mares, effectively blocking opportunities for other mares.
Reduced progeny yield leading to a potential decrease in racing success necessitates broader investigations.
Management of Reproduction and Foaling
Pregnancy Diagnosis Methods
Ultrasound: Usable from day 10 post mating (routine around day 14).
Rectal Palpation: Effective from day 18 but becoming less reliable for twin identification beyond this point.
Clinical Pathology Samples:
Oestrone Sulphate: Detectable from day 60, indicates viable foetus and placenta.
Equine Chorionic Gonadotropin (eCG): Present between days 40 and 120, used for viability assessment (note that false positives occur due to fetal loss).
Routine Pregnancy Examination Timeline
Day 14 post ovulation (before day 16) - initial check.
Day 25-28 post ovulation - check for viability.
Day 40-49 - necessary when the stud fee may be expected.
Day 60-70 - fetal sexing is possible at this stage.
Twins in Thoroughbred Breeding
Incidence of Twins: Up to 10% of Thoroughbred conceptions are dizygotic twins, but viability is low when left alone—only 2-4% remain viable.
Risks include potential abortion of both embryos, uterine scarring, and retention of placenta thereafter necessitating veterinary intervention.
Intervention is manageable prior to day 16 while embryos are still movable, allowing for separation.
If pregnancy is terminated before day 35, the mare can resume cycling and further attempts for a single pregnancy can be initiated post-separation.
After this period, endometrial cups form and produce eCG, sustaining di-oestrus state regardless of the embryo viability.
Parturition Overview
Gestation Length: Typically between 320 to 365 days, average around 340 days.
Most mares foal during the night or early morning hours.
Stages of Parturition:
Stage I (1-4 hours): Signs include restlessness, sweating, and laying down.
Stage II (5-20 minutes): Rapid delivery of the foal; longer than 60 minutes could be fatal for the foal.
Stage III (1-3 hours): Expulsion of the placenta.
It is crucial to have knowledgeable staff present to manage emergencies during this period.
Management of Perinatal Foals
The care of foals around birth is labor-intensive and requires monitoring for:
The time it takes for foals to stand and suckle; assistance might be necessary.
Maiden mares may present increased difficulties during foaling.
Colostrum intake is critical within the first few hours for immune protection.
Watch for conditions such as neonatal isoerythrolysis.
Farm Models, Facilities, and Stocking Density
Inputs and Outputs
Income:
Service fees
Agistment fees
Sale of yearlings
Sale of semen/embryos
Costs:
Set-up costs:
Land, buildings, fencing, facilities
Purchase of stallions, mares
Feed costs
Running and maintenance costs
Labour costs:
Full-time staff; Casual staff (seasonal)
Veterinary costs; Farrier
Stud-Owned vs Client-Owned Mares
Stud-Owned Mares:
Provide a crop of yearlings that can be sold (or raced)
Control over quality and performance of progeny
Fewer concerns regarding biosecurity
Client-Owned Mares:
Walk-up clients – no agistment
Must show evidence of negative swabs
Return must occur if not in foal
Agistment from pre-service up to Day 49 positive (foaling at home thereafter)
Swabs organized by stud
Pregnancy must be confirmed before returning
Agistment allows for pregnancy maintenance and foaling at the stud, with staff on hand to assist
Stud Fees
Service Fees:
Range from $2000 – $400,000
Payable within 30 days of a live foal (or free return service if paid before)
No service fee due if no live foal (e.g., resorption, abortion, stillborn)
Contracts:
Service contract
Mare management contract
Agistment Fees
Extras:
Veterinary procedures (or contract)
Vaccinations, worming
Laboratory analyses (swabs)
Land Requirements
Paddocks and fencing considerations:
Maiden/barren mares (both stud-owned and client-owned)
Pregnant mares
Mares and foals
Foaling paddocks
Small paddocks for mares and young foals
Paddocks and yards for yearlings (plus horsewalker)
Paddocks dedicated to hay or cropping
Stocking Densities
Dry Sheep Equivalent (DSE):
A unit of measure used to compare between animals
Calculating Current Stocking Rate:
Stocking rate (DSE/hectare) = Total DSE’s ÷ Total grazing hectares
Example:
365.5 DSE ÷ 40 Hectares = 9.0 DSE/Ha
Calculating Property Carrying Capacity:
Factors to consider:
Location, topography, and size of the property
Type of stock and stage of life
Pasture mix: annual vs perennial
Pasture health and composition
Supplementary feeding volumes and quality
Nutrient status, physical condition, and biological health of the soil
Rainfall, temperature, frost
Seasonal conditions and weather trends
Note: Carrying capacity can change depending on the time of year.
Facilities
Buildings:
Breeding barn
Foaling boxes
Regular boxes
Stocks area for veterinary examinations:
ultrasounds, pregnancy diagnoses (PDs), uterine flushes, biopsies, and caslicks
Teasing area
Other Facilities:
Small lab set up for semen evaluation
Staff facilities
Area designated for yearling training
The Breeding Barn
Characteristics:
Contained area with a soft surface
Wall to prevent mare from turning around
Usually staffed by 3 personnel
Personal Protective Equipment (PPE) for staff: head and body protection
Safety measures for stallions: boots on mares
Horse Management and Biosecurity on Stud Farms
Biosecurity on the Stud Farm
Aims:
Keep the stallion infection-free
Maximize pregnancy rates
Avoid abortions
Prevent infections from entering the stud broodmare herd
Requirements:
Isolate new or infected horses for at least 2 weeks, monitoring for signs of ill health
Keep equipment used for different horses separated
Separate horses into subgroups to minimize the risk of disease spread
Prevent nose-to-nose contact and sharing of water troughs between paddocks:
Utilize fenced vegetated buffers or natural boundaries.
Testing Mares for Infections Before Serving
Key goal: Keeping the stallion infection-free!
Testing Procedures:
Most mares:
Swab from clitoral fossa prior to oestrus covering
Swab from endometrium at the oestrus of covering
For walk-in, high-risk mares:
Must have swab negative before arriving at stud
Testing for pathogens:
Contagious Equine Metritis (Taylorella equigenitalis)
Klebsiella pneumoniae and Pseudomonas aeruginosa (and occasionally other bacteria)
Blood Tests for Viral Infections:
EHV 1 and 4
Equine Viral Arteritis (EVA)
Brood Mares
Types of Brood Mares:
Maiden: Not previously had a foal
Barren: Previously had a foal but not currently pregnant
Brood Mare: Currently pregnant, may or may not have a foal at foot
Nutritional Management:
Rising plane of nutrition (flushing) at least 4-6 weeks prior to covering
Maintain body condition score (BCS) not exceeding 3 out of 5 to avoid obesity
Breeding Soundness Assessment:
Necessary for barren mares prior to breeding
Management of Pregnant Mares
Nutritional Requirements:
Good quality protein, energy, vitamins, and minerals
Energy requirements increase significantly only during the last 3 months of gestation; adapt supplemental feeding accordingly
Maintain moderate to good body condition (BCS 3 out of 5) while preventing excessive fatness to avoid laminitis or hyperlipaemia in ponies
Keep mares rugged during winter and/or bring indoors at night
Health Management:
Regular vaccinations and worming
Equivac?
Booster vaccination for tetanus and strangles one month prior to foaling
Regular hoof and dental care
Minimize stress around parturition
Management at Foaling
Monitoring and Assessment:
Round-the-clock monitoring using CCTV and foal alarms
Experienced staff and a veterinarian must be on call
Environment:
Foaling occurring in a box or a small clean grass paddock
Have stored colostrum available in the freezer
Prepare mare milk replacer
Option of having a lactating mare or nanny mare in case of orphan foal
Management of Young Horses
Foal Management
Health and Nutrition:
Coprophagic behaviour necessitates regular worming starting from 2-3 months to prevent intestinal obstructions caused by ascarids
Vaccination:
Begin vaccinations around 3-4 months of age once maternal antibodies are waning:
Tetanus and Strangles vaccines are commonly administered
Hendra virus vaccine is recommended particularly in NE Australia
Handling:
Introduce creep feed starting from 4-6 weeks, aiming for up to 1 kg per day by 3-4 months
Weaning of Foals
Timing:
Usually around 6 months of age to allow mammary glands to recover before the next foal
Weaning coincides with housing mares during autumn
Health Considerations:
Weaning can induce stress; foals need to be in optimal health
Transition requires change in diet and microflora, which impacts the immune system
Methods of Weaning:
Sudden or abrupt weaning
Gradual weaning
Paddock or interval weaning (in batches)
Utilizing an older nanny (mare or gelding) can aid in the transition for younger horses
Weanling Management
Dietary Needs:
Requires a balanced, palatable diet that is relatively high in protein (15%) and includes adequate vitamins and minerals for optimal growth (greater than 1 kg/day)
Care must be taken to avoid excessive caloric intake which can lead to developmental orthopaedic diseases (DOD)
Regular worming essential to prevent ascarids
Horse Sales and Preparation
Horse Sales in Australia
Sales Types:
Private sales
Major auctions, e.g., Inglis
Sales are a major income source for stud farms
Successful Presentation:
Well-presented yearlings are more likely to fetch better prices
Successful sales enhance the stud's reputation, attracting more clients
Quality horses are sent to top trainers for training/performance
Winning horses can lead to higher service fees for stallions
Timing of Sales:
Yearling sales typically occur in February, March, April, and May
Other sales include weanlings and broodmares in May, June, and July
Preparing Yearlings for Sales
Individual Development Plans:
Tailored feeding plans for each yearling
Training includes acclimatization to grooming, handling, tying, and hoof care
Exercise regimen implementation is crucial for conditioning
Sale day presentation strategy is essential
Skilled casual workforce, often from overseas, is employed for support
Specific Requirements for Yearlings
Conditioning Needs:
Must exhibit sound growth (fed three times a day with high digestible energy while avoiding developmental orthopedic disease)
Key attributes: sound conformation, lean musculature, fit appearance
Controlled Conditioning Program:
Techniques include:
Hand walking
Jogging (15-20 minutes, undertaken once or twice daily)
‘Ponying’ alongside another horse or behind an ATV
Utilizing round yard lunging or mechanical horse walker
Veterinary Involvement
Pre-Purchase Examinations:
Routine veterinary attendance at all major thoroughbred yearling sales
Typical components:
Soundness/conformation examination
Clinical examination (may be limited during sales)
Pre-sale endoscopic examination of laryngopharynx
Interpretation of repository radiographs
Yearling Radiology
Standard Practice in Thoroughbred Industry:
Typical requirement: 36 radiographic views of limbs and joints
Radiographs must be obtained within six weeks of sale and submitted to sales company repository
Enables veterinarians to view prior to auction for informed decision-making
Provides both vendor and potential purchasers with detailed and accurate health reports, including risk assessment for sale or racing.
Risk Rating Definition for Repository Radiographs:
Low Risk:
No or very minor radiographic changes, unlikely to affect future racing capacity.
Low to Moderate Risk:
Minor changes with good prognosis, not likely to affect racing abilities.
Moderate Risk:
Changes requiring treatment; may impact racing career duration.
Moderate to High Risk:
Changes likely to affect training capability and career longevity.
High Risk:
Changes primed to cause lameness impacting training ability and racing prospects.
Developmental Orthopaedic Disease (DOD)
Types of DOD:
Osteochondrosis (OC): Failure or abnormal maturation of cartilage
Osteochondrosis Dissecans (OCD): Progressed OC resulting in cracks and fissures in cartilage
Physitis (Epiphysitis): Inflammation of the physis or metaphyseal growth plate
Angular Limb Deformities (ALD): May be congenital or acquired, commonly requiring correction
Flexural Deformities: Impediment in the ability to straighten or extend legs, resulting in knuckling appearance
Subchondral Cystic Lesions: Secondary to OCD or trauma to weight-bearing joints
Cuboidal Bone Malformation: Delay in endochondral ossification of cuboidal bones in the knee
Causes of DOD:
Contributing factors include trauma, rapid growth rates, large body size, hormonal variations, and genetic predispositions
Nutritional Influence:
Excess energy intake, inadequate protein, imbalance of calcium and phosphorus, and trace minerals deficiency are critical factors