Stuart buys in day-old pullets and rears them to 16 weeks before they are transferred into enriched colony cages. Here the chickens are in lay for around 56 weeks.

He says: "We're rearing up to 150,000 pullets at any one time and keep up to 400,000 layers."

The Merial Avian Team introduced Stuart to the benefits of Vaxxitek HVT+IBD soon after it was launched.

He was particularly interested because Gumboro vaccines can be very hot vaccines that can damage a bird's immune system.

He says: "Anything that could reduce that stress at that critical age around four to five weeks sounded like something we should try. Now we are using Vaxxitek for all our birds.

"These days we don't need to worry about it because all the Vaxxitek vaccinations are done at the hatchery. We do some blood testing, which Merial will help us with as part of the service at four weeks to make sure the vaccine has been administered well at the hatchery. The Merial Avian team gives us support and advice relating to that.

"The benefits for us in terms of Vaxxitek are a more even flock of layers when they're moved into the colonies, plus lower mortality throughout rearing. It helps them with uniformity so we can treat 16,000 birds as though they are one bird."

Stuart says that health is especially critical on a multi-age site where any problems can soon sweep through the site, and affect all the birds. Merial Animal Health Avian Manager UK &ROI Helen Houghton MRCVS says: "Bird Bros have their own rearing units as well as their laying units. It's a lovely business where it's just their own birds and they pay great attention to biosecurity.

"We work very closely with C & P Bird Brothers' vets, Crowshall Veterinary Services in Norfolk. When the chicks arrive on farm we're involved at taking blood samples at four weeks. They'll go back to Crowshall vets where they'll be tested and we can see the response to the Vaxxitek vaccination at the hatchery."

To view a video clip of Stuart Bird's production facility click here.