Many people in several countries worldwide, particularly in Asia, India, and South America, are getting more financial possibilities to buy animal protein. This fact, combined with the changing diets of these people in those countries, will result in an increase of the worldwide demand for animal products (meat, eggs, and milk) of 70% by 2050. Consequently, the number of livestock is increasing, while at the same time, the number of farmers is decreasing. This results in much bigger herds per farmer. It has become impossible for farmers to follow all of their animals in a reliable way in such big groups. At the same time, several issues must be solved now in the livestock sector, such as monitoring animal health and welfare, reducing the environmental impact, and assuring the productivity of the process. Precision livestock farming (PLF) aims to offer a real-time monitoring and managing system for farmers. This is fundamentally different from other approaches that tried to monitor the animal welfare by human experts scoring animal-based indicators. These methods do not improve the life of the animal under consideration. It is nice to detect a problem after an animal has arrived at the slaughterhouse, but it is much better to detect a problem while the animal is being reared and to take immediate management action. The idea of PLF is to provide a real-time warning when something goes wrong so that immediate action can be taken by the farmer to solve the problem. To bring PLF technology further into field application, increased development and testing of PLF technologies is required in real farms to implement reliable solutions. To further develop and introduce such supporting management PLF systems, some basic principles must be respected.