UK Dairy Day, which would have taken place on September 16 at Telford International Centre, has now been postponed until September 15, 2021.
Organisers said government guidelines had "not provided the assurance" for the event to go ahead, due to the large visitor numbers anticipated.
The annual event brings together about 9,000 people from all facets of the dairy industry, including farmers, students, breeders, geneticists, vets, feed merchants, dairy equipment suppliers and milk buyers – plus professional service providers, charities and colleges.
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Sue Cope, UK Dairy Day event director and CEO of Holstein UK, said it was with a "heavy heart" that the event had to be cancelled.
"Since UK Dairy Day started in 2014, it has provided farmers and the industry with a fantastic opportunity to network, do business and view a superb show of dairy breeds.
"We thank everyone for the support, however in light of lead times that are required by many of our exhibitors we have had to make the difficult decision to postpone.
"Our top priority has to be the health and safety of our visitors, exhibitors, employees, venue support team and the wider community,” Ms Cope said.
UK Dairy Day 2021 is expected to welcome the return of 300 trade exhibitors, 9,000 visitors and cows that showcase the standard of UK dairy cattle.
"In the meantime please stay safe and be proud of the commitment and hard work that British dairy farmers and the industry have delivered during these uncertain times," added Ms Cope.