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Impact of genetically modified plants as feed on animal health and productivity

Broadening Horizons N°16, March 2015

By Gerhard Flachowsky, Friedrich-Loeffler-Institut

Plant breeding can be considered as the starting point influencing the whole food chain. High yield, stable and highly digestible plant biomass with low external inputs of non-renewable resources, such as water, fuel, arable land, fertilizers, etc.; low emissions of gases with greenhouse potential during cultivation; high resistance against biotic and abiotic stressors including adaptation to potential climate change; and a low concentration of undesirable substances in the plants are real challenges for plant breeders in the future. 

Unlimited resources such as sunlight, nitrogen and carbon dioxide as plant nutrients from the air as well as the genetic pool of microbes, plants and animals can be used to develop optimal plants. It is possible to realize all these objectives by conventional plant breeding, but genetic engineering may be faster and more precise (Tester and Langridge, 2010). Both “breeding technologies” – conventional and genetic, should not be considered as either or but as the technologies that complement one another. Presently, the public discussion is polarised on which plant breeding method to adopt and the discussions revolve around pros and cons of conventional breeding and genetic engineering. In this short article a case has been made that inclusion of genetically modified plants(GMPs) in animal diet is safe for animal and human health.

Cultivation and feeding of GMPs

The global area used for cultivation of GMPs increased from 1.6 million ha in 1996 to 181.5 million ha in 2014. About 12% of arable land is currently cultivated with GMPs (primarily soybean, maize, cotton and rapeseed), mainly with plants of the so-called ‘first generation’ i.e. those with increased resistance to pests and tolerance against herbicides, but without substantial changes in composition and nutritive value.

The cultivation and feeding studies on laboratory and food-producing animals carried out to evaluate GMPs for human, animal and environmental safety were based on the principle of ‘the substantial equivalence’ (equivalent to non-GM-counterparts). For the first generation GMP this principle has  been described in Flachowsky (2013) and Van Eenennamm and Young (2014), and is summarised in Table 1. Animal health as well as the composition, quality and safety of food of animal origin were not significantly influenced by feeds from GMPs and were similar with those obtained using the isogenic counterparts in diets. Van Eenenaam and Young (2014) illustrated that over 100 billion animals have consumed GMPs with no unfavourable or perturbed trends in animal health and productivity.

In addition to traditional feeding studies with all types of food-producing animals, many long term studies (23) and multiple generation feeding studies also  exist (19 as summarized by Ricroch et al. 2013). On the other hand, there are a small number of experimental feeding studies and publications with controversial results, which have  recently been assessed/analysed by Van Eenennamm and Young (2014).

Table 1: Summary of published data in peer reviewed journals to compare feeds from GMPs of the firstgeneration with their isogenic counterparts in food-producing animals (for details see Flachowsky, 2013)


Number of experiments

Nutritional and safety assessment


Dairy cows

Beef cattle






No unintended effects in composition and contamination of GMP compared with isogenic counterparts (except lower mycotoxin concentrations in GMP with Bacillus thuringiensis (Bt))


No biologically relevant effects on feed intake, digestibility or animal health, and no unintended effects on the performance and fertility of animals or on the composition and quality of food of animal origin.


Recombinant DNA and newly expressed proteins in GMP do not show  chemical/physical properties different from those in native plants




Laying hens






Fish, rabbits etc.




Further objectives of plant breeding

The current and future goals of plant breeding are to improve the composition and the nutritive value of GMPs (e.g., to increase the content of some nutrients, such as fatty acids, amino acids, minerals, vitamins and other substances such as enzymes). This is also called biofortification of plants. Other aims are to reduce the content of undesirable substances such as lignin, phytates, glucosinolates, alkaloids, mycotoxins, etc. in plants or to increase their resistance against insects and plant diseases. Such GMPs are terms as second generation GMPs, which have improved output traits. Presently, developments of more than 100 GMPs are under research in many countries (see Tillie et al., 2013).

Tolerance of plants against herbicides and resistance against pesticides may have some advantages for producers and farmers; while, biofortification may increase the content of various nutrients in food of plant and animal origin and may contribute to a better human nutrition in many developing countries. Some examples of the second generation GMPs are: “Golden rice” (rice rich in ß-carotene); high lysine maize, low phytate maize etc. But there is no urgent need for biofortification in developed countries from the animal nutrition perspective, because many feed additives are available for use in animal rations (see Flachowsky, 2013 for further details). On the other hand, biofortified plants, as well as plants which use limited resources efficiently (plants with increased water and nitrogen use efficiency) may substantially contribute to nutrition and food security of smallholders in many developing countries (Ruane et al. 2013; Harvie 2015). These countries would be able to produce more feed and food under their conditions without large external inputs.


Plant breeding has large and strategic potential for global feed and food security. Both breeding technologies, conventional and genetic may contribute to solving important challenges, such as sustainable use of limited global resources, improved use of unlimited resources, adaption to climate change and lowering of global greenhouse gas emissions. More publically supported research is urgently needed in this field. All methods of plant breeding that lead to an increase in resource efficient production and a stable yield of available biomass should be used/combined. An extensive review of peer-reviewed literature on food producing animals fed diets containing GMP-feed has revealed no unexpected perturbations or disturbing trends in animal performance or health indicators. Also there is no evidence that safety and quality of animal products from animals fed GMPs are compromised.


Gerhard Flachowsky, Institute of Animal Nutrition, Friedrich-Loeffler-Institut (FLI), Federal Research Institute for Animal Health, Bundesallee 50, 38116 Braunschweig, Germany; Tel.: +49 531 514112; e-mail: gerhard.flachowsky@t-online.de

References for additional information

  • Flachowsky, G. (Ed., 2013) Animal nutrition with transgenic plants. CAB International, Vol. 1, Biotechnology Series, Wallingford and Boston, 234 p.
  • Harvie, A. (2015) Food Security: Challenges, role of biotechnologies and implications for developing countries. Nova Science Publishers; 183 pp.
  • Ricroch, A.E., Berheim, A., Snell, C., Pascal, G., Paris, A., Kuntz, M. (2013): Long-term and multi-generational animal feeding studies. In: G. Flachowsky (Ed.) Animal nutrition with transgenic plants. CABI Biotechnology Series, Wallingford and Boston; pp. 112-127.
  • Ruane, J., Dargie, J.D., Mba, C., Boettcher, P., Makkar, H.P.S., Bartley, D.M., Sonnino, A. (2013) Biotechnologies at work for smallholders: Case studies from developing countries in crops, livestock and fish. Occ. Papers on Innovation in family farming. FAO 2013; Chapter 5; 173-198
  • Tester, M., Langridge, P. (2010) Breeding technologies to increase crop production in a changing world. Science, Vol 327, 818-827 (12.02.2010).
  • Tillie, P., Dillen, K., Rodriguez-Cerezo, E. (2013) The pipeline of GM crops for improved animal feed: Challenges for commercial use. In: G. Flachowsky (Ed.) Animal nutrition with transgenic plants. CABI Biotechnology Series, Wallingford and Boston; pp. 166-192.
  • Van Eenennaam, A.L., Young, A.E. (2014) Prevalence and impacts of genetically engineered feedstuffs on livestock populations. J. Anim. Sci. 92, 4255-4278;