Your Reading List

Bull essentials

Spring essentials for a successful breeding season in your cow-calf operation include the following.

  • Test the bulls.
  • Vaccinate before breeding season with a modified live (ML) IBR and BVD vaccine.

Test the bulls

A bull is more than a pasture ornament. He has an important job to do and if he can’t, he shouldn’t be there. A breeding soundness evaluation should be done on all bulls by your veterinarian 30 to 60 days before the bulls go out. It is an effective way to identify poor potential breeders before the breeding season and replace them.

One in five bulls taken from a random population will be unsatisfactory. Poor semen quality, physical defects or lack of libido are reasons for bulls’ failure.

After a bull tests satisfactory, it is still important for producers to watch the bulls closely for the first few breedings. If the bull is not interested in the cows or has physical defects that prevent successful breeding, he should be culled. Why keep a dud? Test the bulls and watch to make sure they can and want to do their job.


Vaccinating the cows and heifers before the breeding season is necessary to prevent fetal losses from viral infections like IBR and BVD. A modified live viral vaccine for IBR and BVD should be given about three weeks before the bulls go out. By vaccinating at this time, cows and heifers will have the highest protection for the viral diseases when they need it most: early pregnancy.

A BVD infection at less than 40 days along in pregnancy causes embryonic death and loss of the pregnancy. A BVD infection from 40 to 125 days along in pregnancy results in calves that are persistently infected (PI) with the virus. PI calves shed lots of virus and spread the infection to others in the herd. It is more work to vaccinate cows in the spring since there are calves to separate. The extra work is worth the effort.

Killed vaccines in the fall just do not provide adequate protection for BVD. Our practice has seen BVD problems in several herds using killed vaccines. An 8-way clostridial vaccine should also be given every year to the cows. If 8-way wasn’t given at another time, it can be given when the cows go through for IBR/BVD.

Don’t forget to vaccinate the bulls with a modified live IBR/BVD vaccine at least three weeks before breeding. A bull with an acute BVD infection can spread the virus to the cows and result in early embryonic death or PI calves. An 8-way clostridial vaccine should also be given every year to the bulls.

A foot rot vaccine is available and may be useful. Talk to your veterinarian.

When shopping for bulls, be sure to ask the vaccination history of the seller’s herd. Nobody should have to buy a bull that is PI with BVD. A simple test on a small sample of skin from a bull can determine whether the bull is PI. Some purebred breeders are testing their bulls for BVD. Sounds like a good idea.

Talk to your veterinarian about which vaccines will work the best for your herd. Remember the spring essentials:

  • Do breeding soundness evaluations on the bulls.
  • Vaccinate with modified live IBR/BVD before breeding.

About the author

Dr. Marian Johnson's recent articles



Stories from our other publications