Genetic conditions in Wagyu
The inherited recessive conditions Wagyu associations test for, what each one does, how results are reported, and how to breed around them.
Every breed has inherited conditions. Wagyu's are well researched — much of it in Japan — and DNA tests exist for the main ones, so they can be managed with careful mating. For how carriers and recessive inheritance work in general, read Genetic defect testing first.
The conditions
The Australian Wagyu Association (AWA) fact sheet names these as the key inherited recessive conditions in Wagyu:
| Condition | Code | What it does |
|---|---|---|
| Spherocytosis (erythrocyte membrane protein Band 3 deficiency) | B3 | A defect of the red-blood-cell membrane. Affected calves develop anaemia; death normally occurs within about a week of birth, and survivors are severely stunted. |
| Chediak-Higashi Syndrome | CHS | Affects white blood cells and the immune response, and slows blood clotting. Often first seen as unusual bleeding from the umbilical cord at calving; affected cattle often have a pale coat. |
| Claudin-16 deficiency (renal tubular dysplasia) | CL16 | Causes progressive kidney failure from late adolescence; affected cattle are unlikely to live beyond about six years. |
| Factor XI deficiency | F11 | A clotting-factor deficiency causing mild, prolonged bleeding after injury or procedures such as castration or dehorning. Generally non-lethal; carrier × carrier matings may also have more difficulty producing viable pregnancies. |
| IARS disorder | IARS | Death of affected calves in the last weeks of pregnancy or shortly after birth; live affected calves are weak, anaemic and prone to infection. |
The AWA notes that other recessive conditions exist in Wagyu — for example Factor XIII deficiency (F13) — that have not been identified in the Australian population. Associations add tests as new conditions are confirmed, so check your registry's current list.
How results are reported
Associations print a status for each condition on the animal's record. The Australian Wagyu Association uses the condition code followed by a suffix, for example:
- F — tested free
- C — tested carrier
- A — tested affected
- FU — free by pedigree (untested, but expected free)
- a percentage — untested; the calculated chance the animal is a carrier based on its pedigree
So "CL16F, B3FU, F1150%" would mean: tested free of CL16, untested but free by pedigree for B3, and a 50% chance of carrying F11.
The American Wagyu Association requires that bulls used for AI and females used as embryo donors be tested for all known genetic recessives and defects, or be deemed free by pedigree, before their offspring can be registered.
Breeding around them
- Never mate two carriers of the same condition. One in four calves would be affected.
- A carrier mated to a tested-free animal produces no affected calves, though about half the calves will be carriers. Test those calves before keeping them for breeding.
- When buying embryos, ask for the results of both the sire and the donor dam.
- When buying semen, plan which of your females it can safely be used on.
Key takeaways
- The main tested Wagyu conditions are B3, CHS, CL16, F11 and IARS; others such as F13 exist.
- Ask for tested results (F/C/A), not just pedigree estimates.
- Never mate two carriers of the same condition.
- Carrier × tested-free is safe, but test the calves before breeding them.