How far can you go when overstocking pens?

The threshold appears to be somewhere between 115 percent and 120 percent, says Rick Grant, director of the W.H. Miner Agricultural Research Institute in Chazy, N.Y. Animal performance and return on capital investment begin to decline at stocking densities higher than that.

A study by the Miner Institute evaluated the effect of approximately 100 percent, 115 percent, 130 percent and 145 percent stocking density of stalls and manger space in a four-row barn. Milk yield didn’t drop as stocking density increased from 100 percent to 115 percent, but it did drop appreciably — from 96.14 pounds per day to 91.08 pounds per day — as stocking density increased from 115 percent to 145 percent.

Lying time was reduced by 1.1 hours per day when stocking density increased from 100 percent to 145 percent. And, cows spent more time standing idly in the alleys as stocking densities increased to the higher levels.

Note that this study was done in a four-row barn. The threshold may be lower than 120 percent in a six-row barn.