Three genetic defects from the real club calf world are in the game: TH (Tibial Hemimelia), PHA (Pulmonary Hypoplasia with Anasarca) and DS (Digital Subluxation). Every animal is Free (no copies), a Carrier (one copy) or Positive (two copies) for each one.
The three defects
- TH enters through Shorthorn lines. Lethal: a TH-positive calf is born deformed and does not survive. Carriers are fine and tend to be stout and big-boned.
- PHA enters through Maine-Anjou lines. Lethal, and dangerous to the cow: a PHA-positive calf swells with fluid late in the pregnancy. Carriers tend to be short-backed, compact and heavy muscled.
- DS enters through Shorthorn lines and is not lethal. DS-positive cattle can look great and breed on, but some express crooked hind pasterns, from mild (some grow out of it) to severe. Which happens depends on the line, and the DNA test cannot tell you which kind you have.
How it inherits
Straight Mendelian genetics. Each parent passes one copy, chosen at random, every calf.
| Mating | Result |
|---|---|
| Carrier x Free | Half carriers, half free. No positives. |
| Carrier x Carrier | 1 in 4 positive, half carriers, 1 in 4 free. For TH or PHA that is a dead calf 1 time in 4. |
| TH carrier x PHA carrier | Safe. The two genes do not interact. |
| DS carrier x PHA carrier | Risky. DS and PHA sit close together; a calf that gets DS from one parent and PHA from the other is often lost. |
| DS positive x PHA carrier | The mating to avoid. Every calf gets DS, half get PHA. |
Breeding carrier to carrier does not raise your odds of a carrier calf. It stays at half; all you add is the dead one. There is no bull that breeds hot for TH or PHA. DS is the exception: some lines throw the crooked-leg version far more often than others, and you learn that by watching what your matings produce.
Finding out
- DNA panel (coins) on any animal, from its page or in bulk from the Herd page. Standard results take a few game days; a rush option returns them immediately.
- By parentage: a calf out of two known-free parents is marked free without a test.
- Affected calves prove their parents. A TH or PHA calf marks both parents as carriers; a DS calf showing crooked legs does the same for DS.
- Necropsy (coins) on a lost pregnancy or a calf that did not survive, when the cause was not obvious.
What carriers give you
Carriers get an edge in the traits that go with each defect, and it shows on the animal whether or not it has been tested. That edge is strongest in young cattle and narrows as they mature, so a clean calf that looks plain at weaning can catch up. DS positives that do not express get a bigger edge still.
PHA warning
If a cow is carrying a PHA-positive calf you get a vet warning late in the pregnancy with the option to take the calf early. The calf is lost either way; taking it early keeps the cow safe. Ignore the warning and she may need an emergency C-section, or you may lose her.
Selling
Known statuses show on cattle pages, the Herd grid, auction listings and semen listings. A bull must have a known TH, PHA and DS status before his semen can be listed for sale.