WikiBreeding & genetics
Genetics & inheritance
Alleles, potential and why a foal can beat, match or fall below its parents.
Every horse carries a hidden genome. A foal gets one copy of each gene from its sire and one from its dam, picked at random, with an occasional mutation. That is why a foal can beat both parents, land between them, or fall below both. It isn’t always a blessing, but it is always a chance.
Potential: the ceiling, not the horse
Genes set a horse’s potential for each of six stats, on a scale of 0 to 1000. Training and racing bring the horse up towards that ceiling; they can never take it past it. Overall potential is the average of the six, and it earns a grade:
| Grade | Potential from | What it means |
|---|---|---|
| S | 900 | Once-in-a-generation |
| A | 800 | Elite, usually several bred generations in |
| B | 700 | A strong, well-bred line |
| C | 600 | Where the first horses top out |
| D | 500 | Ordinary |
| E | 0 | Weak |
- Speed: top speed in the race.
- Stamina: how long it holds that speed; matters more the longer the trip.
- Burst: the kick in the final furlong.
- Durability: resistance to injury and fatigue.
- Adaptability: copes with a surface or trip it doesn't prefer.
- Temperament: consistency from race to race; a hot-headed horse pulls hard early and wastes energy.
Two copies of every gene
Each stat is a pair of numbers (alleles), one from each parent. The horse shows a blend that leans towards the better copy: the weaker copy plus 55% of the gap. A second gene pair, class (vigour), adds or takes away up to 150 on every stat at once. That gene is why some foals are simply a cut above.
Mutations
Each stat allele has a 6% chance to mutate by up to 30 points when it is passed on. At no inbreeding, half of mutations help and half hurt. Inbreeding raises both the mutation rate and the share that hurt (see Inbreeding & kinship). Mutations also lean towards the family’s centre, and they can never carry a foal outside its family limits.
By the numbers live from the rules
- Higher copy's weight in the blend
- 55%
- Class (vigour) range
- -150 to +150 on every stat
- Mutation chance per stat allele
- 6%
- Largest mutation step
- 30 points
- Extra mutation chance per 10% inbreeding
- 3%
- Share of mutations that hurt (no inbreeding)
- 50%
A real example
Two horses generated by the game, paired, then bred 400 times by the same code that breeds your foals. The numbers below are worked out when this page is built, so they change if the rules do.
Foal potential, 400 foals (parents marked)
The rules’ exact odds for this example pairing, worked out from the two example horses’ true genes (mutations left out; 400 foals are only a sample, so the two can differ by a few points). The breeding screen never shows numbers like these for a real pairing: they would give the horses’ hidden genes away. It shows a few possible looks and an outlook in words, worked out only from what is public about the two horses. For this pair (the dam as your mare) it would read: “Usually close to your mare, with a real chance to beat both parents.” Good nick.
The rules' exact odds (example horses only) live from the rules
- Middle 80% of foals
- 469 to 680
- Beats both parents
- 46%
- Below both parents
- 53%
- Family limits
- 282 to 869
- Nick rating
- 65 (Good)
Expected foal potential per stat, from the rules (not shown on the breeding screen).
The nick rating, worked out
The nick sums up how well two lines combine: how often a foal beats both parents (upside), how settled the foal’s best trip and surface are (a coherent type), and how inbred it is. The breeding preview shows only its label, as a word (“Good nick”), and feeds it public facts only: the outlook’s chance to beat both parents, whether the parents’ published best trips agree and whether their surfaces agree (a full share when they match, half when they don’t), and the kinship. The formula, with the weights the game uses:
| Label | Nick from |
|---|---|
| Excellent | 70 |
| Good | 55 |
| Fair | 40 |
| Poor | 0 |
The example pairing's nick live from the rules
- Base
- 25
- Beats both parents (46%)
- +27.5
- Most likely trip (50%)
- +7.5
- Most likely surface (50%)
- +5
- Inbreeding (0 per mille)
- −0
- Nick
- 65 (Good)
A nick is a summary, not a verdict: two pairings with the same nick can differ a lot in their best and worst foals. Read it with the outlook and the possible looks.
Dominant, recessive and hidden copies
Besides the stats and the coat, every horse carries 14 more genes for patterns, body and performance. Each comes in two copies like the rest, and how the copies combine depends on the gene. A dominant gene shows with one copy. A recessive gene shows only with two, so a horse can carry one copy without showing it and pass it on. With an incompletely dominant gene, one copy shows a little and two copies show fully.
| Gene | Inheritance | What it does | Most common in |
|---|---|---|---|
| Champagne (Ch) | Dominant | Gold, amber or sable body, pink freckled skin | Quarter Horse 2%, Paint Horse 2%, Mustang 1% |
| Silver (Z) | Dominant, black pigment only | Black turns chocolate with a flaxen mane; invisible on a chestnut | Mustang 6%, Quarter Horse 1% |
| Pearl (prl) | Recessive | Two copies: pale apricot; one copy shows only next to cream | Andalusian 12% |
| Tobiano (TO) | Dominant | White patches across the back, dark head | Paint Horse 55%, Mustang 8%, Quarter Horse 1% |
| Leopard complex (LP) | Incomplete dominant | One copy: spots with Pattern-1, else varnish roan; two: few-spot | Appaloosa 60%, Mustang 3% |
| Pattern-1 (PATN1) | Dominant, needs LP | Turns leopard complex into full leopard spots | Appaloosa 40% |
| Splash white (SW) | Incomplete dominant | Big blaze, white legs, blue eyes; two copies: bald face | Paint Horse 8%, Quarter Horse 3% |
| Height (Ht) | Incomplete dominant | Taller per copy: more speed and stamina, less burst and durability | Warmblood 85%, Friesian 75%, Thoroughbred 60% |
| Feathering (fe) | Recessive | Long hair on the lower legs | Friesian 100%, Warmblood 5% |
| Speed gene (MSTN C) | Incomplete dominant | C/C sprinter, C/T miler, T/T stayer | Quarter Horse 80%, Paint Horse 75%, Thoroughbred 45% |
| Big heart (bh) | Recessive | Two copies: extra stamina potential | Akhal-Teke 8%, Thoroughbred 6%, Arabian 4% |
| Iron legs (IL) | Dominant | Lower injury risk | Mustang 30%, Standardbred 20%, Marwari 20% |
| Curled ears (Ce) | Dominant | Inward-curling ear tips | Marwari 95% |
| Dished face (Dh) | Incomplete dominant | A slight or a classic Arabian dish | Arabian 85%, Marwari 20% |
Size, the speed gene and big heart change the stat potentials, and the family limits include them. The twelve breeds and what they carry are on Breeds & body genes; the new colours and patterns are on Coats & markings.
What else is inherited
- Distance: sprint, mile, middle or staying genes set the trip a horse is happiest at.
- Surface: turf or dirt; a horse with one of each copes better on both.
- Running style (front-runner, stalker, closer) and maturity (early, normal or late peak).
- Breed: the foal’s breed percentages are the exact average of its parents’, see Breeds & body genes.
- Size and the speed gene: they move points between stats and shift the best trip, never the total.
- Coat and markings: real horse colour genetics, see Coats & markings.
- Quirks such as mudlark (loves soft ground) or gate-shy, some dominant, some recessive; they only show themselves in races (see Quirks below).
- Fragile legs, the risk that comes with breeding from injured horses: Fragile legs.
Quirks: the catalogue
A quirk is a small inherited habit that only matters in some races. It never shows on the horse page until it is discovered: in a race where the quirk shows itself, there is a 35% chance it is noticed afterwards. From then on it is known for good, listed under Quirks on the horse page, and you get a note in your Stable news saying what it means. A Pedigree Scan narrows the potential ranges but does not reveal quirks: only racing does.
| Quirk | Shows itself | Effect in those races | Inheritance | Share of first-generation alleles | What to do |
|---|---|---|---|---|---|
| Mudlark | on soft or heavy going | +150 adaptability, +15 speed | recessive: shows only with two copies, so carriers pass it on unseen | 20% | Wet ground is the day to look for: soft or heavy going may suit. |
| Gate-shy | in every race, from the stalls | −90 temperament | dominant: one copy shows | 5% | Nothing to fix, it is in the genes; worth knowing before you breed. |
| Late kick | in every race, at the finish | +45 burst | recessive: shows only with two copies, so carriers pass it on unseen | 25% | A finishing burst may suit a stalker or closer plan. |
| Crowd-shy | on big days (Features, Season Finals, Group races) and in any field of 12 or more | −110 temperament | dominant: one copy shows | 4% | Smaller fields may suit better than the big days. |
The effects add to the horse’s stats for that race only (stats run from 0 to 1000; see Stats & aptitudes). A horse can carry a recessive quirk without ever showing it, so two clean parents can still throw a mudlark.