Precision livestock farming is becoming ever more relevant as the agricultural industry struggles to come to terms with aspects such as animal welfare, animal disease, the environment, economics, traceability, robots and livestock management. Whilst some benefits have proved elusive, others contribute positively to today's agriculture. Research continues to be necessary and needs to be reported and disseminated to a wide audience. These proceedings contain the reviewed papers from the 4th European Conference on Precision Livestock Farming. The papers reflect the wide range of disciplines that impinge upon precision livestock farming including feeding dairy, data quality, poultry and pig applications, livestock environment, wireless sensing, dairy fertility and calving management, animal identification, mastitis detection and locomotion. The broad range of research topics reported are a valuable resource for researchers, advisors, teachers and professionals in agriculture. Also note that the reviewed papers from the 7th European Conference on Precision Agriculture are presented in a companion publication.