**Preface to "The Tight Junction and Its Proteins: More Than Just a Barrier"**

Most accredited FAO statistics predict that in 30 years, the world's population will have reached 9 billion people. In order to satisfy the nutritional needs of humans, the demand for raw materials, especially protein sources, will increase. It has been estimated that by 2050, the production of meat will have increased by 50%, while the demand for fish, milk, and eggs will have grown by 75%. An increase in animal products requires an increase in farmed animals, and this will be accompanied by a significant intensification in livestock farming (higher animal densities and production units, more concentrated feed, pharmaceuticals, and vaccinations, etc.). A large number of animals, farmed in relatively small areas, will result in a larger demand for protein and energy sources on which to feed them and in the deposition of large amounts of excreta, containing nitrogen, phosphorus, organic matter, and fecal microbes, in the water, with a consequent contamination of water systems globally, which will include surface water eutrophication and groundwater nitrate enrichment. Thus, the livestock sector is an important user of natural resources and has a great influence on air, soil, and water quality, the global climate, and biodiversity maintenance. Our research proposes innovative ideas to control the environmental damage through the management of animal nutrition. At the same time, the perception of animals as sentient beings capable of feeling emotions, like joy and pain, will increase in prevalence in the future. Thus, it will be increasingly important to adopt nutritional strategies and breeding techniques capable of increasing animal welfare and at the same time to reduce the use of pharmacological treatments in full respect of the environment, animal health, and food safety.

> **Michael Fromm, Susanne M. Krug** *Editors*
