Managing the use of stock bulls

Stock bulls will continue to be a vital part of breeding plans on many farms in 2025. Managing the transition from AI to stock bull usage is an important factor in breeding success.

Did you experience a lull in calving in 2025? Often, this coincides with the introduction of a bull. In many instances, the stock bull has spent months on a silage-only diet doing minimal daily walking, and is then turned out one day and expected to achieve 100% cover of cows in heat. This is unrealistic.

Monitoring

Bulls should be monitored throughout the winter and spring for body and hoof condition. Check feet at least one month pre breeding, and do a fertility test. Trace minerals such as zinc, copper and selenium are important for performance and fertility – supplement for at least six weeks pre breeding.

Introducing the bull and bull:cow ratios

Continue to AI along with the introduction of the bull(s) for at least a week to give him a chance to settle in. The other common pitfall is the number of bulls. There doesn’t appear to have been an increase in the number of bulls on most farms in recent years despite the increase in herd size. It is recommended to have:

• One young bull for every 10 empty females,
• One mature bull for 20-30 empty females.

If more than two cows are in heat per mature bull on one day, then these should be inseminated. Finally, for herds using synchronisation programmes in either heifers or cows, it is best to AI the first round of repeats, as the numbers will be in excess of what bulls will be capable of physically dealing with in such a short space of time. Don’t undo all your efforts by failing to do this.

The above article first appeared in the Teagasc Dairy Advisory Newsletter for May, prepared by Dr. Joe Patton, Head of Dairy Knowledge Transfer at Teagasc. Access the full Teagasc Dairy Advisory Newsletter (PDF) here.