The XIIIth International Symposium on Ruminant Physiology (ISRP) was held in Leipzig, Germany, in September 2019. This symposium continues a tradition which has started almost 60 years ago when the first ISRP was held in Nottingham, UK, in 1960. Since then it took place throughout the world. With Leipzig, the ISRP has been carried out in Germany for the second time after 1994. It has always been the basic idea of this symposium to bring scientists from all over the world together in order to present and to discuss new findings on basic aspects of ruminant physiology and to develop new concepts on systemic physiology in ruminants. More than 500 participants from 36 countries joined the ISRP in Leipzig. The scientific presentations consisted of 18 invited keynote presentations and 262 short communications which were either given as oral communications or as posters. The short communications were published in Advances in Animal Biosciences Volume 10 Issue 3.

Whereas the classical topics such as gastrointestinal digestion, absorption and secretion, ruminant intermediary metabolism, regulation of feed and water intake, the rumen as mediator between diet and host metabolism, reproduction, lactation and growth, comparative and integrative physiology and the ontogenesis of the newborn ruminant were of major relevance as in previous symposia several new and highly actual topics have also been integrated into the programme. These topics included inflammation and immunology, lifespan and productivity, biosensors and big data management and global change and ruminants underlining the incorporation of new research areas in ruminant physiology. They also reflect an increased relevance and public perception of animal husbandry regarding global climate changes as well as sustainable food production. The present special issue of Animal includes 18 full papers originating from respective keynote presentations in each session. These contributions have always been published in the “traditional” print version and have thus always been evaluated as a valuable source and update of the understanding of ruminant physiology.