Genetic Defects in Beef Cattle

Genetic defects are inherited conditions that can cause calf loss or poor performance. Most are managed by knowing the carrier status of the animals you buy and breed.

Key points

Many defects are recessive, so carriers can look normal.
Breed associations track defects and report carrier status.
Ask sellers for test documentation before buying.
Plan matings with your vet and association guidance.
Have your veterinarian examine problem calves and keep records.

How inherited defects work

Many genetic defects are recessive. A calf shows the condition only when it inherits the faulty gene from both parents. Animals with one copy are called carriers and usually look normal.

That is how a defect can spread unnoticed through a herd or breed. Two carriers mated together can produce affected calves, even though neither parent shows anything wrong.

Some defects have been known in a breed for many years, and tests are routine. Others are discovered in newer lines, so check for updates each year. If two carriers have already been mated, talk to your vet about what to expect and how to handle the calves.

What breed associations do

Breed associations track known defects in their breed, publish information on how to test for them and often report carrier status in registration records. Rules differ from one association to another, and they change as new tests become available.

Check with your association for the current list of conditions and testing options.

Many associations post a list of conditions and testing requirements on their websites. Read the list for your breed, and for the breeds in your crossbred cattle. Associations also publish updates when new conditions are found, so make a habit of checking the news each year.

Ask before you buy

When buying a bull or a female, ask whether the animal has been tested or is known to be free of the defects relevant to its breed. Ask for documentation instead of relying on a verbal answer.

A good seedstock producer will answer these questions plainly and show you the records.

If a seller does not know the status of an animal, treat that as important information. You can ask for testing before purchase, or choose another animal. A seller who is open about test results is usually a seller worth doing business with.

Which conditions are tracked in this breed?
Has this animal been tested, and where is the report?
What is the status of his sire and dam?
How does the herd manage carriers?

Managing carriers in a herd

Carriers are not always removed from a herd. Some producers choose to use them with careful mating plans that avoid pairing two carriers, while others prefer to cull. The right choice depends on the condition, the animal and your goals.

Talk with your veterinarian and your breed association before deciding, and keep clear records on every mating.

Because of how recessive genes work, carriers can spread quietly in a herd for years. Testing breeding stock is the best way to take control. Never ignore a pattern of calf loss in one line of cattle, even if each case looks like bad luck by itself.

Signs of a possible defect

Stillborn calves, calves born with visible abnormalities or calves that die soon after birth can have many causes, including infections and nutrition. A genetic cause is only one possibility.

Call your veterinarian to examine problem calves. Do not guess, and do not handle suspect animals or tissues carelessly. If your vet suspects a reportable disease, follow instructions to contact the state veterinarian or USDA APHIS.

Keep any tissue or samples that your vet needs for diagnosis, and follow your vet's directions about handling. Some conditions need special sampling to be confirmed.

Records and testing plans

Keep detailed records of births, deaths and any abnormalities, including sire and dam. These help your vet and your association trace patterns.

Ask your vet and association about testing for conditions that apply to your herd, and set up a plan for testing new purchases.

Good record keeping includes sire, dam, birth date, birth weight and the outcome of every calf, including those lost. A pattern can emerge from the records that no one calf shows. Share relevant findings with the seller and the association. This helps other producers as well.

Common mistakes and what to ask

Buying untested animals, mating two carriers by accident and ignoring unexplained calf losses are the usual problems. Another is assuming a defect is not an issue in your breed.

Ask your association which conditions apply, ask your vet to examine problem calves and ask sellers for test documentation.

Do I know which conditions apply to my breed?
Are purchases tested or documented?
Do I record calf losses and causes?
Did my vet examine problem calves?

When to get help: Call your veterinarian to examine stillborn or abnormal calves, and ask your breed association about testing options. If a reportable disease is suspected, contact the state veterinarian or USDA APHIS.

Sources and further reading

Organization homepages are linked so you can search them for current guidance on this topic.

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