Genetically modified feeds and their effect on the metabolic parameters of food-producing animals: A review of recent studies

The land area devoted to the cultivation of genetically modified (GM) plants has increased in recent years: in 2012 such plants were grown on over 170 million hectares globally, in 28 different countries, and are at present used by 17.3 million farmers worldwide. The majority of GM plants are used as feed material for food-producing farm animals. Despite the facts that GM plants have been used as feed for years and a number of feeding studies have proved their safety for animals, they still give rise to emotional public discussion. This paper reviews and discusses the results of recent experiments on the effects of feeds derived from genetically modified plants (GM feeds) on the physiological and metabolic indices of livestock, poultry and fish. The number of peer-reviewed papers on studies evaluating the influence of feeding food-producing animals with genetically modified materials is high. Most of these studies were carried out with GM plants with improved agronomic traits, i.e. herbicide-tolerant crops and crops protected against common pests; however, in some experiments, GM crops with enhanced nutritional properties were assessed. In the relevant part of these studies, not only production parameters but also different indices of the metabolic status of animals were analysed, and only a few minor differences with no biological relevance were found in livestock or poultry experiments. A greater number of minor effects on selected metabolic parameters were detected in fish studies; however, the causes of these differences were unclear and it is difficult to determine whether they were due to the genetic modification of the GM feed materials used. Since the results presented in the vast majority of experiments did not indicate any negative effects of GM materials, it can be concluded that commercialised transgenic crops can be safely fed to target food-producing animals without affecting metabolic indices or the quality of such products as meat, milk and eggs.