European farm ministers agreed Monday to new rules for slaughterhouses intended to minimize suffering of animals when they are killed.

The new rules, which take effect in 2013, will require slaughterhouses to incorporate animal welfare into their designs. Slaughterhouses will be required to regularly monitor techniques for stunning animals before slaughter to ensure that animals don't regain consciousness before they are killed.

Slaughterhouses must appoint an official in charge of animal welfare and require staff to be properly trained and certified, according to the new rules.

Almost 360 million cattle, sheep, pigs and goats are slaughtered each year in the European Union, along with "several billion" chickens, the commission said. An additional 25 million animals are killed for their fur in the E.U. annually.

Large livestock farms and slaughterhouses have become a growing presence in central and Eastern Europe, prompting concerns from some authorities about their impact on the environment and public health. Smithfield Foods Inc. (SFD), one of the largest livestock farm operators in the region, didn't immediately respond to a request for comment on the new rules.

-By Matthew Dalton, Dow Jones Newswires; +32 2 741 1487; matthew.dalton@dowjones.com