Which animal?
Which genes does each parent show?
Read them off each animal's panel. Animals with no known parents count as wild: each hidden copy is Good 20%, Ok 50% and Bad 30% until what they show rules some out.
Know more? (optional)
Family, hidden copies and family markers sharpen the odds. Leave them alone for two unrelated wild animals.
Genes of their parents (the grandparents)
Each grandparent you fill in replaces the wild guess for that line. Two Bad parents can only make a Bad/Bad young, for example.
Hidden copies you know
The copy an animal carries but does not show, if you know it: a Good animal from a Bad parent carries Bad, for example. A server admin can read both copies with livestock.showgenes.
Inbred parents and family markers
Each gene of the calf
chance it shows each copy| Gene | Good | Ok | Bad | Pure Good | |
|---|---|---|---|---|---|
| Dung | 80% | 17% | 2.8% | 31% | Good 11%, Ok 56%, Bad 33% / Good 11%, Ok 56%, Bad 33% |
| Longevity | 80% | 17% | 2.8% | 31% | Good 11%, Ok 56%, Bad 33% / Good 11%, Ok 56%, Bad 33% |
| Yield | 80% | 17% | 2.8% | 31% | Good 11%, Ok 56%, Bad 33% / Good 11%, Ok 56%, Bad 33% |
| Fertility | 80% | 17% | 2.8% | 31% | Good 11%, Ok 56%, Bad 33% / Good 11%, Ok 56%, Bad 33% |
| Hardiness | 80% | 17% | 2.8% | 31% | Good 11%, Ok 56%, Bad 33% / Good 11%, Ok 56%, Bad 33% |
An inbred calf still carries these copies and passes them on; only how well its genes work drops.
How livestock breeding works
Every cow, bull and sheep carries two copies of each of its 5 genes (Dung, Longevity, Yield, Fertility, Hardiness), each Bad, Ok or Good. The better copy is the one that shows and the one that works. The other stays hidden but can still be passed on.
A newborn takes one copy of each gene from its mother and one from its father, each picked at random like a coin flip. So two Good/Good parents always make a Good/Good calf, while two Good/Bad parents make one that shows Bad 1 time in 4. Bred genes never change at random.
Each animal also carries two of 16 family markers, one from each parent. When its two markers match it is inbred, and every gene counts for half: a Good gene works like Ok, for example x1 Yield instead of x1.6. Two unrelated animals have an inbred calf 1 time in 16; siblings or a parent and its young share markers, so the chance goes up.
A mother with Good Fertility, not inbred, has twins 60% of the time; never more than 3 young at once. Read more on the livestock page or breed plants with the genetics calculator.
Methodology
The odds are worked out exactly from the breeding rules, over every copy each animal could carry. Milk and wool per harvest by Yield gene were tested in game on our own server. Tested on the current version of Rust.