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Herd Fertility – is your bull working?

5 July 2023

This is part of the FAS Beef Technical Toolkit series, designed to give farmers practical timely advice to aid decision-making throughout the year.

Fertility is a key driver of suckler herd profitability so ensuring bulls are fit for purpose is essential, as bulls are responsible for 50% of your herd’s fertility. Now that bulls will have been out with cows for at least one cycle it is important to make sure that cows are holding to service, as pregnancy scanning reports a historic event when it is too late to resolve the problem.

It is important to check for cows repeating (bulling) every 21 days, as sub-fertility is common among bulls with an average of 1 in 5 bulls tested sub-fertile. Subfertility could be due to testicle size or sperm quality.  A sub-fertile bull will get some animals pregnant, but this will take longer and several services, making the problem harder to identify, especially in systems where bulls are rotated during mating.  Bull rotation will help to reduce the severity of a sub-fertile bull, however, it is highly likely that the problem bull will go unidentified. It is important to remember that bulls tested prior to mating can underperform. For example if they pick up an infection, become lame or have libido problems or have sustained penis damage, therefore monitoring groups for returns is crucial to ensure issues are identified before these impact herd fertility.

If you suspect a bull is not working then the sooner this is addressed the better, to allow for alternative bulling arrangements.  Contact your vet as soon as possible in order to tackle the problem early on in the breeding season and arrange for a Bull Breeding Soundness Examination (BBSE) to be carried out which will include collecting and evaluating semen.

As part of the Scottish Government’s ‘Preparing for Sustainable Farming’ there is funding available under the animal health and welfare interventions for bull fertility assessments, providing an opportunity to work alongside your vet to take preventative action. Speak to your local vet for advice and further information.

Related FAS Materials 

The Cost Of Bull Infertility | Helping farmers in Scotland | Farm Advisory Service (

Agribusiness News February 2023 - Management Matters: Not a Lot of Bull! | Helping farmers in Scotland | Farm Advisory Service (

Related External Material

Preparing for Sustainable Farming full guidance (


Written by - Sarah Balfour

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