Members of Unison in Scotland, England and Wales will walk out from 6.30am on Tuesday and Wednesday.
The move follows a ballot earlier this month, in which members voted overwhelmingly for strike action over an imposed pay offer of 0.75 per cent.
Unison has urged the Food Standards Agency (FSA) to resolve the dispute through independent conciliation.
General secretary Dave Prentis said: "Staff in slaughterhouses work in some of the most dirty, difficult and stressful conditions, surrounded by blood and faeces, to keep the public safe from contaminated meat.
"It is only fair that our members receive a pay increase that is at least in line with inflation. They should be recognised for the vital role they play in safeguarding the human food chain against harmful and repulsive dirt and diseases.
"It is not too late for the FSA to avoid the prospect of a strike that may well clear supermarket shelves and butchers' shops of meat in the barbecue season."
The union is seeking an above-inflation pay rise it says would make up some of the 15 per cent lost from FSA staff pay since the Coalition Government came to power.
A spokesman for the FSA said it is is disappointed Unison has called industrial action next week "when Unison has said it is committed to ongoing talks with us."
He said talks with the union continue but if there was a strike it should not affect meat supplies to shops.