Alison Van Eenennaam, extension specialist in animal genomics and biotechnology at the University of California, Davis, explains, “Genetically engineered crops are digested by animals in the same way as conventional crops. Evidence to date strongly suggests that feeding livestock with genetically engineered crops is equivalent to feeding unmodified feed sources in terms of nutrient composition, digestibility and feeding value.
It has been estimated that between 70-90 percent of harvested GM crops are fed to food-producing animals, making the world’s livestock populations the largest consumers of the current generation of GM crops.  GMOs have never been detected in the milk, meat or eggs derived from animals fed GM feed.
 Eenennaam, A. V. Journal of Animal Science and Biotechnology. GMOs in animal agriculture: time to consider both costs and benefits in regulatory evaluations, 4. Retrieved from http://www.jasbsci.com/content/4/1/37