Animal feed tainted with a banned hormone has prevented farmers across the EU selling animals or milk while an investigation struggles to trace the feed.

A number of farms in most of the 15 European Union Member States have been affected, with some farms closed, pending checks for presence of the banned hormone, since late last week, reports Reuters.

The feed is contaminated with the hormone medroxyprogesterone-acetate (MPA). The contaminant emanated from the now-bankrupt Belgian company Bioland and ended up in feed sent to around half of the pig farms in the Netherlands.

Jack Luiten of farmers' umbrella group LTO-Nederland, was cited by Reuters as saying yesterday [Wednesday] that Dutch authorities and farmers were optimistic, after a Tuesday meeting of EU veterinary experts, that an EU ban on some Dutch exports would be withdrawn by the end of the week.