A review of the welfare of dairy cows in continuously housed and pasture-based production systems

14 There is increasing interest in the use of continuous housing systems for dairy cows, 15 with various reasons put forward to advocate such systems. However, the welfare of 16 dairy cows is typically perceived to be better within pasture-based systems, although 17 such judgements are often not scientifically based. The aim of this review was to 18 interrogate the existing scientific literature to compare the welfare, including health, 19 of dairy cows in continuously housed and pasture-based systems. While 20 summarising existing work, knowledge gaps and directions for future research are 21 also identified. The scope of the review is broad, examining relevant topics under 22 three main headings; health, behaviour, and physiology. Regarding health, cows on 23 pasture-based systems had lower levels of lameness, hoof pathologies, hock 24 lesions, mastitis, uterine disease, and mortality compared to cows on continuously 25