Is Genetically Modified Food Permissible in Islam?
Question

What is the ruling on eating the meat of animals that have been fed with plants that have been genetically modified?
Praise be to Allah.Understanding Genetically Modified Foods
Research is still ongoing into the effect of genetically modified plants on humans, plants, animals and the environment, and even on the economy. There are still specialists who advise not hastening to accept what appears to be the case with regard to genetically modified plants of abundant production and the ability to overcome defects and resist disease. 
Global Perspective on GMOs
There are two main points of view with regard to this issue: the first is that which is adopted by American companies and American government organisations, which is to allow the use of genetically modified plants and marketing of their products. The other view, which is the opposite view, is that which is adopted by the European Union, which bans cultivation (of genetically modified plants) in its territory and warns against its possible consequences. 
The matter is still not definitive with regard to its effects, because it needs years for the impact to materialise, according to specialists. The fact that we have some plants which are more resistant to pesticides means that they will be used a great deal, which will pose a danger to the environment and human health. The fact that the plant has this strength means that it will enter the body of the one that eats it. As is well known, the countries that import these plants will never be able to plant the seeds of these plants in their lands again. What this means is that they will remain under the control and domination of the companies that produce these seeds, and this is what will affect the quality of the plants produced and will affect the economy of the importing country, as it will continue importing and consuming, and not producing independently. 
The Arab Organisation for Agricultural Development held a conference in Sudan 15-17/6/2003 CE, the subject of which was: Evaluating the Environmental Impact of Introducing Various Kinds of Genetically Modified Plants and Animals. 
We will quote from that conference statements which will explain this issue, before ruling on what was mentioned in the question. 

 (On p. 45) Dr. `Awad-Allah ibn `Abdullah `Abd Al-Mawla — Prof of Horticulture and Genetics in the College of Agriculture, Khartoum University — says:

What are genetically modified products?
This is a phrase which refers to the products of some crops which have been genetically engineered, which means introducing a foreign gene to the original genetic material. The foreign gene may come from different sources, and is introduced to increase the value and improve the genetic qualities of the genetically engineered plant. Usually plants are genetically altered for two purposes, namely:

To reduce the cost of producing these plants, by making the plant resistant to disease.
To improve the quality of the product, by improving its appearance or nutritional components with regard to qualities that have to do with manufacturing and storage.

Production of these genetically modified products is done using genetic engineering techniques. This involves first identifying the gene responsible for the desired quality and isolating it, then introducing it to the living being (the receiver). After this new gene has been mixed with the genetic material of the genetically engineered plant, it is possible to increase the number of cells in which the new gene is successfully mixed, then by means of tissue planting it becomes possible to produce complete plants from the cells, and these plants become genetically modified or engineered. Once this gene becomes well established in the genetically engineered plant, it becomes possible to transfer it to other types of the same crop by using traditional methods of raising plants, by means of hybridisation and crossbreeding. 

In a paper entitled Genetic Modification: Justifications, Benefits and its Impact on the Environment and Society, by Dr. Lakhdar Khalifi and Dr. Majidah Khalifi, it says (p. 15):

In the field of genetic modification in particular, there is a clear difference between American and European law. Whilst American law regards genetically modified foods as natural foods that do not pose any danger until proven otherwise, European law — especially French law — regards genetically modified foods as unnatural and a possible source of danger until proven otherwise. End quote. 
Is Genetically Modified Food Permissible in Islam?
The one who researches this issue cannot state that it is prohibited to eat genetically modified crops and fruits unless it is proven for certain that they are harmful. This does not mean that we can be careless about this matter, because of what we have pointed out above of the possibility that they may pose a danger in many ways, and because people still prefer natural plants and crops, and people like them even if they are more expensive. 
The matter still needs more research and more time until the effects of these plants and the harm they may cause becomes clear. 
Until it is proven that they are harmful, the basic principle is that these plants are permissible and it is permissible to eat animals that have been fed on these plants, but it is also essential to be cautious about what these plants may cause in the future, and it is essential to follow up on research and information about these plants. 
For more details, please see the following answers: 21582 , 119830 , 155691 , 308325 .
And Allah knows best.