Factors Affecting Bull Fertility
by Ryon Walker , Ph . D . Livestock Consultant
Significant emphasis has been placed on the importance of fertility in the female , whether in the cow or a developing heifer . When we address fertility in one female , we are affecting one offspring . When we address fertility in one male , we could be affecting up to approximately 35 offspring in a single year . Is this oversight on bull fertility because bulls are overlooked until it is time to turn them out for the breeding season ? We know that reproductive failures can occur in any cow-calf operation and can be costly . Let ’ s take the bull out of that negative equation and take a look at the top 6 factors I believe affect bull fertility .
2 . Physical Characteristics
You can identify subfertile bulls with the help of a breeding soundness exam ( BSE ). A BSE consists of a scrotal circumference measurement ( indicator of puberty and serving capacity ), physical evaluation ( indicator of mating ability ) and a semen exam ( assessment of motility and morphology ). A BSE should be conducted at 30 to 60 days prior to the first day of the breeding season to allow time for a re-test of a bull that was questionable in passing ( classification deferred ) or a replacement if he does not pass a BSE ( unsatisfactory breeder ). A study conducted at
1 . Disease
A good herd health program is invaluable , especially for the bulls . A health program in bulls reduces or eliminates the risk of transmitting diseases that can cause reproductive failure in females at different stages of pregnancy . Conditions such as Leptospirosis , Vibriosis , Trichomoniasis , Bovine Viral Diarrhea ( BVD ), IBR- Infectious Bovine Rhinotracheitis ( Red Nose ) and internal parasites can all contribute directly or indirectly to reproductive failure in the female . Diseases such as Lepto and Vibrio ( bacterial diseases ) and Trich ( protozoal disease ) cause abortion within the first three months ( Lepto and Trich ) or during mid-gestation ( Vibrio ) after infection and is transmitted directly between animals . These diseases can be vaccinated and managed for .
66 • OCTOBER 2020