For some time we have been trying to find hen food free from genetically modified maize. Up until a year ago this was quite possible, we do grow a small amount of non-GMO maize but insufficient for our needs. In desperation we have contacted the Junta in Santiago de Compostela but received no reply, we then contacted Greenpeace who were helpful but confirmed our worst fears. It appears that the consumer has no say in these matters and the corporations have won. Below is the reply from Greenpeace.
Spain is the biggest grower of MON810 - GE maize - in the EU, and subsequently it is very hard to find uncontaminated maize. We have spoken to various large scale organic farmers and producers and many are resigned to importing GE free maize from France. I think your best bet would be to feed the chickens something other than maize that is still grown in Spain.
I will forward your message to our Spanish office as well, and ask them to contact you if they have more information, although Greenpeace does not endorse specific products/brands, they may be able to help you.
I hope this helps.