The Yorkshire Agricultural Society announced the cancellations yesterday, saying it was a decision which had not been taken lightly.
The move follows reports of a pig showing signs of illness at another recent show.
In an updated statement issued today, the Society, said that the stricken pig's diagnosis could not be established before the Great Yorkshire Show starts in Harrogate on Tuesday.
The statement reads: "We have taken the decision to cancel all pig classes at this year’s Great Yorkshire Show.
"This is not a decision taken lightly and has been taken as a matter of precaution due to one report of a pig showing signs of illness at a recent show.
"The pig was examined by a vet at the show and a sample has been sent off for laboratory analysis. The results of the test will not be known until Tuesday this week, at the earliest.
"Animal welfare is of paramount importance to us and Great Yorkshire Show organisers have taken this step as a precautionary measure to eliminate any potential risk."
The 161st Great Yorkshire Show takes place in Harrogate from Tuesday until Thursday.