Modern dairy cows are typically culled at 3-4 years of age despite a natural lifespan of 20 years, driven by high milk yield breeding that causes accelerated physical decline.
The pursuit of maximum milk yield has created a biological arms race that shortens dairy cow lives dramatically. Lameness affects 25-30% of cows at any time; mastitis is endemic in many herds. Repeat dystocia (difficult calving) from small pelvis relative to calf size causes pain and injury. Longer-lived, lower-yield breeds managed on pasture show better welfare across most metrics.