Lying time is one of the most validated welfare indicators in dairy cattle science. Cows have a strong behavioural need to lie for 10–14 hours daily; restrictions below 8 hours indicate significant welfare compromise. Causes of reduced lying time include overstocking (limited cubicle access), poor cubicle design, lameness, and heat stress. Studies demonstrate that every hour below optimal lying time is associated with increased lameness risk, elevated cortisol, and reduced milk production. Precision livestock farming technologies — including pedometers, accelerometers, and pressure mats — enable continuous lying time monitoring at herd and individual level. Welfare assessment protocols (Welfare Quality, AHAW) use lying time as a Tier 1 outcome measure. Farm benchmarking data show average lying times of 9–11 hours in well-managed herds versus 6–8 hours in poorly managed ones.