Various research studies show that the overcrowding dairy cows in pens will have detrimental health effects for the cows, mainly due to the increase in standing time which can lead to loss of resting time and hoof problems.

According to the Miner Institute, 120% may be the maximum “stocking density” of cows before detrimental health effects are seen. Above that limit, cows sacrifice feeding time to make up for lost resting time, spend more time standing or waiting in alleys to lie down, and are unable to recover from resting deprivation once it exceeds 2-4 hours per day.

A separate Canadian study showed that cows decreased lying times by two hours, from about 13 hours per day (at 100% stocking density) to 11 hours per day (when stocking rates climbed to 150%). The Miner Institute’s research showed that every hour lost in resting time results in a loss of 3.7 pounds per cow per day in milk production.

Researchers also found that somatic cell counts tend to increase as a result of greater stocking density, from less than 150,000 cells/ml at stocking rates below 113% to more than 225,000 cells/ml at a stocking density of 142%. Finally, there is also a tendency for more clinical cases of mastitis when more cows are crowded in the same pen.