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Preparing Bulls for the Breeding Season

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Bulls are the most costly animals on a cow-calf operation and provide the majority of genetic improvement for the cow herd.  It is not uncommon for producers to rough bulls through the winter since they do not have the nutritional requirements that gestating cows do.  However, it is important that bulls are not forgotten as the breeding season approaches.  For producers with a limited 60 day breeding season it is critical that bulls are healthy and sound going into the breeding season.   The extremely cold winter may have damaged the testis of bulls if they did not have adequate dry bedding.  Frostbite of the scrotum will not have any long term effects but if the epididymis was damaged the bull will no longer be a viable breeder.

A breeding soundness exam (BSE) is critical to determine if the bull will be capable of getting cows bred this year.  A BSE should include a good physical exam paying close attention to eyes and feet and legs.  Bulls need to be able to see and travel in order to breed cows.  The testis and seminal vesicles should be palpated to make sure they are normal.  Lastly the semen should be evaluated for morphology and motility.  If a bull does not have normal active sperm he can be re-evaluated in 30 days.  If BSEs are delayed there is no time to correct any abnormalities and re-evaluate.

If new bulls are being brought onto the operation they should have a BSE if they have not already had one recently.  All new bulls should also have been tested for Bovine Viral Diarrhea Virus (BVDV) and Johne’s disease.  If new bulls are not virgin bulls, they should also be tested for Trichomoniasis prior to breeding any cows.  A vigorous preputial scraping with a sterile plastic infusion pipette is the best sample to detect Tritrichomonas foetus in bulls.  The ISU Veterinary Diagnostic Laboratory has recently implemented a PCR test for Tritrichomonas that is more sensitive and faster than traditional culture methods.  Contact the Veterinary Diagnostic Laboratory for any questions on sampling methodology or sample handling.

While the bull is in the chute for the BSE it is a good time to vaccinate and de-worm them.  Vaccination with a modified live virus vaccine should be done at least 30 days prior to the breeding season so spermatogenesis is not impacted.  Although most mature bulls do not have severe internal parasite problems during the breeding season they cannot afford any nutritional drain from parasites. 

Another overlooked aspect of bull management is their physical condition.  Bulls should be in good flesh but not overly fat going into the breeding season as they will lose weight during the breeding season.  Make sure that thin bulls are not pushed to fast with a high concentrate diet.  Acidosis, abomasal ulcers, liver abscesses or seminal vesiculitis can ruin a bull prior to the breeding season if concentrates are not managed properly.  Bulls should be in good physical shape as they will need to travel extensively during the breeding season.  The most efficient method is to put the bulls in large pasture with the water at one end and feed or salt at the other to force the bulls to walk.  


 Dr. Grant Dewell

Dr. Grant Dewell

Veterinary Diagnostic and Production Animal Medicine
2412 Lloyd Vet Med
Iowa State University
Ames, IA  50011

Ph: 515-294-2822
Fax: 515-294-1072