11. Technology of race horse breeding 말의 육종 기술

A11. Technology of race horse breeding. Traits, and genetic improvement of race horses

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Race horses – Thoroughbreds (totally pure) usually use.

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Flat racing horses: Usually retire earlier. Good stallions  More value as stud.

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Jump racing horses: Fit horses may continue racing up to 12 years

Running racehorses:

Primary trait is speed at gallop (basic thoroughbred selection), although has low heritability (h2=0.2-0.3) -> No great correlation with sire performance & offspring performance

Problem in that TBs often bred more for name/pedigree rather than actual ability

Also primary traits: time, accumulated prize, amount of money, handicap number

Secondary traits: Stamina, persistence in performance, early maturity.

Sex is also important (colts)

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thoroughbred breeding season in northern hemisphere runs from Feb-June/July (TBs born in northern hemisphere are considered 1 year older on 1st Jan, in southern hemisphere they are considered 1 year older on 1st Aug) -> Aim is to ensure foals are born in the earliest months of year to ensure as much time to mature before racing.

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Must use live cover.

AI would lead to further narrowing of gene pool (one stallion could cover thousands of mares)

Dramatic fall in covering fees (bad for stud farms)

More difficult record keeping/pedigree documentation

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Breeding stallion – May cover 4 mares per day (7am, midday, 4pm, 8pm & midnight if absolutely necessary). Must allow some flexibility for when mares are ovulating.

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Mares – Checked for inoculations (venereal diseases etc), tail bandaged, washed down, covered with leather cape (to prevent being bitten by stallion) & back hooves booted (a kick in the knackers could put stallion out of action for ~10days)

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Traits of harness racing horses

- Trotting

- Test for speed & trotting skill, in sulky or under saddle with rider & cumulated prizes (h2=0.2-0.3)

   measurable traits : Average ~1 min 20 sec for 1000m

- Pacing : Quicker than trot. Mainly American Pacer horses.

- General traits to look for: conformation, temperament, ability, movement.

- Time, cumulated prize, amount of money, handicap number etc are also considered as racehorse traits.

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Genetic improvement: the speed gene in race hoses:

- MAS (Marker assisted selection) based on speed gene

- Myostatin (MSTN) is a strong inhibitor of muscle formation

Identified in several other mammals: whippet & Belgian blue cattle

MSTN Isolated and sequenced from a thoroughbred

- Mapped to Equine chromosome 18 (ECA18)

- Point mutations found in MSTN

- One of them was switched from cytosine to thymine within MSTN gene: Can determine racing performance

- Tb horse classified in 3 genotype groups:

   - C/C genotype: best in short distance races

   - C/T genotype: good for middle distance races

   - T/T genotype: greater stamina and are the majority of winning horses at longer distance races.

   - C allele is the mutation

   - T allele is common in many horse breeds and wild horses (ancient allele)

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Selection and tasting for speed gene can improve thoroughbred horse breeds

Crossing heterozygotes: C/T mare + C/T stallion can produce either a C/C (25%) or C/T (50%) or T/T (50%)

Breeding by genetics:

Breeding by genetics: genetic and genomic breeding value:

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Equinome Elite Performance test: in Ireland & UK

The Test checks 70.000 gene/ allele variants in search of critical genes for producing a more consistent success. Each horse that is tested gets a genomic racing value of 1-5, where 1 indicates the horses with the greatest genetic potential

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​Breeding by genomic inbreeding (parents are closely related genetically)

Homozygosis: nr. of identical variants that are identifiable in both parent’s genomes will result in highly homozygous horse

Each horse is ranked as low, medium or high for genomic inbreeding.

Speed gene test

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Horse selection and breeding strategies (systems):

outbreeding – from parents not closely related

Inbreeding- from related animals, especially from many generations

Line breeding- milder forms of inbreeding

Horse selection on the basis of:

Conformation

Breeding performance

Racing performance

Pedigree of stallion/ dam

Price of the prospective covering

Racing performance of the dam & sire