Hay Farm on Ford and Etal Estate was given the score after assessment on March 23, the Food Standards Agency's website shows.
Inspectors gave a ‘major improvement necessary’ verdict on its management of food safety.
However, owner Viv Cockburn explained that it is a paperwork issue rather than anything to do with the food.
"We started processing our rare breed pork on site and it’s the paperwork side of that that led to the rating,” she said. "It’s nothing hygiene-wise.
"We’ve had ongoing discussions with an environmental health officer and because the correct paperwork was not in place they had to grade us that way.
"We’ve now got all that paperwork in place and are more than happy that a reassessment will be done.
"In one sense it's good thing that they’re not just looking at the hygiene of a place and that they take into account the paperwork management.”
The venue was rated ‘generally satisfactory’ for hygienic food handling and ‘good’ for cleanliness and condition of the facilities and building.
The Cockburn family have been running a centre for the breeding and showing of Clydesdale and other heavy horses for several years.
The enterprise was run as a working farm with displays of antique farm and heavy horse equipment as well as interpretation and education features to help visitors understand the importance of heavy horses in the history of agriculture in Northumberland.
The family also became involved in the breeding of rare pigs (British Lop) to keep stock levels up.
During the Covid pandemic, a small retail area was created to allow the sale of pork from the rare breed pigs along with a cafe.
The inspection findings means that of Northumberland's 634 restaurants, cafes and canteens with ratings, 562 (89%) have ratings of five and just two have zero ratings.
The scheme gives businesses a rating from 5 to 0 which is displayed at their premises and online so you can make more informed choices about where to buy and eat food.
5 – hygiene standards are very good
4 – hygiene standards are good
3 – hygiene standards are generally satisfactory
2 – some improvement is necessary
1 – major improvement is necessary
0 – urgent improvement is required