In 2007, a formal apology for slavery H.Res. 194 entered the United States congress and was later passed unanimously by the senate.
For centuries, animal rights/welfare activists have made the comparison between slavery and animal agriculture. Writing in 1789, Jeremy Bentham said
The day has been, I grieve it to say in many places it is not yet past, in which the greater part of the species, under the denomination of slaves, have been treated ... upon the same footing as ... animals are still. The day may come, when the rest of the animal creation may acquire those rights which never could have been withholden from them but by the hand of tyranny. The French have already discovered that the blackness of skin is no reason why a human being should be abandoned without redress to the caprice of a tormentor. [...]. The time will come when humanity will extend its mantle over everything which breathes... "
Peter Singer wrote in 1974,
Our custom is all the support that the meat industry needs. The decision to cease giving it that support may be difficult, but it is no more difficult than it would have been for a white Southerner to go against the traditions of his society and free his slaves: if we do not change our dietary habits, how can we censure those slaveholders who would not change their own way of living?
Many contemporary thinkers have anticipated a massive ethical shift against the current treatment of animal as property, once tasty artificial meat is developed. If future humans become regretful of our current treatment of animals, will there be an official apology from a government?
This question resolves positively if a sovereign government (at the level of national, or an international government if one exists at the time) issues a formal apology for the poor treatment of farm animals in the past, specifically in reference to the fact that they were treated as property before January 1st 2200. Otherwise it resolves negatively.
For clarification, a sovereign government is defined as one that has "the full right and power of a governing body over itself, without any interference from outside sources or bodies. In political theory, sovereignty is a substantive term designating supreme authority over some polity." The United Nations does not count as a sovereign government.