Ensuring Herd Health and Fertility: The Importance of Bull Soundness Testing

While much attention is given to the health and fertility of cows, the breeding bull is equally crucial in minimising the empty rate in the dairy herd. Thinking of the seasons where you have had unexplained poor heifer in-calf rates or a high empty rate following a good 6-week in-calf rate, it is more than possible that your bulls have failed you. This is where bull soundness testing becomes an important management tool.

What is Bull Soundness Testing?

Bull soundness testing is an evaluation of a bull’s physical health, reproductive capability, and semen quality. The test may include:

• Clinical examination and screen for common diseases
• Reproductive organs check: Inspection of the scrotum, testes, and penis for abnormalities or injuries. Scrotal circumference is closely correlated to daily sperm output, so we measure this to give an indication of their capacity. A rectal examination of the accessory glands, e.g. the prostate and vesicular glands.
• Semen evaluation: Collection of semen using an electroejaculation technique or artificial vagina. Electroejaculation works by stimulating the nerves which control the emission of semen. Our trained veterinarians are experienced at minimising any discomfort and use a very low level of electrical stimulation. Using this method allows us to test around one bull every 10 minutes. Microscopic examination of that semen then occurs immediately on farm to assess sperm motility, concentration, and morphology.
• Libido assessment: Observing bull behaviour with a restrained on-heat heifer to ensure normal mating drive. This is not usually done alongside electroejaculation but rather instead of, and semen can be examined microscopically if collected into an artificial vagina at this time.

When should you test your bulls?

We recommend you do bull soundness testing annually, prior to mating. We find that, in regularly tested bulls, around 10% will drop in fertility from season to season for various reasons. For yearlings, or bulls who have not been screened prior, approximately 20% may be found to be sub-fertile, depending on how well fed and healthy they have been prior.

Why test?

Even though we often put out surplus bulls in the dairy herd and with our heifers, if you have one dominant bull who is infertile, he can have a significant impact on mating outcomes.

Where you have synchronised cows or heifers at the start of mating, bulls will need to be of a high fertility to ensure all returns are successfully covered.

What do I need for the soundness test using electroejaculation?

• A good crush, where the bull can be restrained safely for a rectal examination and that has access via the side so we can catch the sample and examine the penis.
• A sheltered area is helpful in which to set up the microscope, and power is required.
• Bulls ideally will not have been working in the 48 hours prior to being tested.

Summary

Investing time and resources into bull soundness testing can significantly impact the reproductive success and profitability of your dairy operation. By ensuring your bulls are healthy and fertile, you support a robust and productive herd for years to come.

For more information on bull soundness testing, please contact your local Vetlife clinic.