Genetic Testing, BVD, & DNA Profiles

BVD-PI Negative

All bulls offered through Midland have been screened for persistent infection (PI) with the bovine viral diarrhea (BVD) virus. This screening provides the Midland buyer utmost confidence that their new seedstock are not “carriers” of the BVD virus.

For cattlemen, the primary concern of spreading the BVD virus is through PI cattle; with transiently (or temporarily) infected cattle considered a less important source of the disease. PI animals are very efficient transmitters of the virus. They usually have a very high and virulent amount of virus circulating in their blood and other fluids; and they shed the BVD virus continually. A PI calf is “created” during pregnancy when BVD virus from an infected dam’s bloodstream crosses the placental wall to her fetus during the first part of gestation. This is the only way a PI animal is created.

Fetal infection can lead to fetal death, the birth of a PI calf, or the birth of a normal calf. It’s important to note that a calf born BVD-PI will always be a PI animal. If a calf is not PI at birth, it can never become PI. While uncommon, PI calves can grow to adult age without any outward signs of BVD virus infection. The virus is perpetuated when these PI animals – bulls or heifers – survive past yearling age and enter the breeding herd. PI heifers or cows that conceive will always produce a PI calf. A PI bull has the dangerous potential to effectively and efficiently spread the BVD virus to all cattle he comes in contact with.

Immunizing cattle herds with appropriate vaccines to protect against transient infection should be the first consideration in a herd biosecurity program. But, given the right conditions, the tremendous amount of virus secreted by a PI calf can overwhelm a level of immunity provided its herd mates by vaccination. The cost of at least one PI animal in a commercial beef breeding herd has been reported to range from $14-$24 per cow per year in reduced reproductive efficiency alone. Research at West Texas A&M University found feedyard PI prevalence to be about 0.17% (1.7 PIs per 1,000 head). This research also indicates the probability of initial treatment for respiratory disease is 43% greater in cattle exposed to BVD-PI cattle in the same pen or an adjoining pen. Therefore, the cost of BVD virus infection is too great to leave to chance. That’s why we recommend that all cattle entering your herd, including your new bulls, be screened for the BVD virus before they enter your operation.

More key points:

  • All open heifers purchased should be screened for BVD-PI status well in advance of breeding.
  • Purchased bred heifers or cows with an unknown BVD-PI status should be kept separate from the resident herd until their PI status can be confirmed by first screening their calves.
  • Screen the all new crop calves in advance of breeding to avoid exposure of a pregnant cow by a PI calf.
  • Cows do not need to PI tested unless they have a PI calf.
  • If an animal tests negative for BVD-PI status, there’s no need to ever retest that animal.
  • PI animals should be isolated from the herd and should never enter commerce.
  • PI surveillance should include the sampling and testing of as many aborted fetuses, stillborns and pre-weaning deaths as possible.
  • All “non-biological” pairs should be screened for PI status – this includes “recipient” cows.
  • Screen all cows that lose a calf and a tissue sample not obtained from the calf.

For more information, contact Clint Peck or Mo Harbac, Montana State University Beef Quality Assurance, 406-896-9068 or 406-994-4323.

Genetic Testing

All Midland sale bulls are AM and NH Free. We submit registration numbers of all sale lots to each respective association who then identifies animals who need tested. Samples are tested by Pfizer/Bovigen and any identified carriers are voluntarily pulled from our sale.

AM Free (Arthrogryposis Multiplex-Curly Calf)

AM carrier
Any animal that carries the recessive AM mutation in its DNA.
Any animal that has been determined to be free of and without the AM mutation.
AM calf
An affected calf born dead with a spine that is bent or twisted, that appears small and thin and has legs that are often rigid and may be hyper-extended.

For more information, visit the American Angus Association website.

NH Free (Neuropathic Hydrocephalus-Water Head)

NH carrier
Any animal that carries the recessive NH mutation in its DNA.
Any animal that has been determined to be free of and without the NH mutation.
NH calf
These calves have a severe phenotype that includes an extremely large cranium with little or no brain and spinal cord present.

For more information, visit the American Angus Association website.

Osteopetrosis (Marble Bone Disease)

Calves born prematurely (10-30 days premature). Typically calves are born dead, but if born alive will die within 24 hours after birth. Calves possess a short lower jaw and impacted molars. Long bones are fragile and can be broken with ease. For more information, visit the Red Angus Association website.

OS-Free (OSF)
An animal is homozygous for the normal variant indicating that they have been tested for the causative mutation and been found to be “free” of the mutation. Therefore these animals are unable to transmit it to any of their offspring.
OS-Carrier (OSC)
An animal is found to be heterozygous or “carrier” for the mutation, meaning that they possess one normal allele and one mutant allele, These animals pass the mutation on to approximately half of their offspring.
OS-Affected (OSA)
Although affected calves are rarely tested, they would be homozygous for the mutation.