Most spring-calving dairy herds typically start breeding in early May, so by now most farmers should have completed four weeks of Artificial Insemination (AI).

The aim is that 90% of all cows to be served will have been inseminated by the end of week three. This is a key target for farmers to hit, who are aiming for a compact calving spread to be achieved next spring.

With most farms nearing the point where enough replacements will have been generated using dairy AI to meet the demands of the herd, depending on the farm, it may be time for the stock bull to be turned out.

Stock bull

For farmers who are using stock bulls to clean up after AI, it is important to spend some time ensuring that the bull is fit for purpose.

It is recommended that you continue to AI cows that come in-heat for at least 10-14, days while the bull settles in with the herd.

The use of beef AI later in the breeding season offers the opportunity to use a panel of beef bulls to match to cows and heifers based on calving difficulty, while also selecting for shorter gestation length.

These checks should include whether or not the animal:
  • Is in good body condition score (BCS);
  • Has no signs of lameness, with good mobility;
  • Most importantly, is fertile.


Research suggests that up to 5% of bulls are completely infertile and a further 15-20% will be partially, or become periodically, infertile.

There are a few potential factors that may result in a level of subfertility, which include: a bull having a low libido; sperm defects; or physical factors affecting bull mobility or mating ability.

To address this, bulls should be fertility tested or, if this is not an option, good data recording should take place with regard to when cows were served, and monitored subsequently to see if any repeats are occurring. 

Bull infertility can be very costly, can further drag out the breeding season and have a negative impact on the 2022 calving season

It’s worth remembering to treat bulls carefully and to ensure that all safety precautions are taken when the bull is running with the herd, in order to keep you and your family safe this summer.