Bull subfertility: How to minimise the risk

In beef production economics, fertility is estimated to be ten times more important than carcass quality and five times more important than growth rate.

- By Dr Stephen Hughes, veterinary specialist, Howick Veterinary Clinic

The key challenge for beef cattle producers is achieving high pregnancy rates within a short breeding season. For this reason, it is essential to evaluate bulls for breeding soundness and ensure that only those with high fertility are classified as sound and used in the herd.

Subfertility in bulls can result from numerous factors affecting semen quality, physical soundness, libido, and serving ability. Estimates from bull populations in North America and Australia suggest that at least 20% of unselected bulls are subfertile or infertile. In a study of 2 110 beef bulls in Western Canada, 34,2% were classified as subfertile due to physical unsoundness and/or inadequate semen quality, with 19% specifically affected by poor sperm morphology. In previously examined bull groups, around 10% may be classified as subfertile. These findings highlight that a bull's fertility can change over time, meaning that in a group of ten bulls, one or two may be subfertile.

The main risk factors contributing to subfertility include illness, injury, disease, heat and humidity, stress, excessive body condition, exposure to toxins, and poor leg or claw conformation.

Breeding soundness evaluations