Use Feed Space to Determine Stocking Ratio
When thinking about stocking density, most dairy farmers will look at the number of cows in a pen and then the number of freestalls in that pen.
That ratio of cows to stalls becomes the pen’s stocking density, but might woefully understate what is actually occurring in the pen, says Dan Weary, an animal welfare specialist with the University of British Columbia.
“Comfortable lying space is key, but so is the amount of feeding space available,” he says. “Many barns are designed and managed to provide one stall per cow [but] still provide too little feeding space. This means the cows can be well stocked for one resource (lying space) but overstocked for another (feeding).”
Weary argues that bunk space, particularly for fresh and early lactation cows, should be the deciding factor. Canadian research shows when bunk space is adequate, at 32" per cow, more than 80% of cows can eat at the same time. But as bunk space decreases, to 24" and even 16", the percentage of cows that can eat at one time drops to 50% and 30%, respectively.
“As expected, this competition at the feeder was greatest when cows returned from milking to fresh feed,” Weary says. “The reduced access resulted in reduced feeding times, and more time standing inactive in the feed alley as cows waited to access feed.”
This has led Weary to tip barn planning and design on its head. “To avoid overstocking at the feed bunk, start your barn planning by making sure each cow will have lots of feeding space, and as a rule of thumb, avoid three-row (and six-row) layouts,” he says.
Rather than figure out how many freestalls can be squeezed into a pen configuration, Weary recommends designing the feed lane first. Figure out how many 32" feed spaces can be accommodated into a given pen length, and then work off that number to determine the number of freestalls that must be fit into the space. The same logic should be used in determining stocking rates of existing pens and facilities.
Stalls matter
Having enough stalls is also crucially important to ensure cows have access to beds and adequate time to lie in them. In another Canadian study, lying time in stalls was reduced by one hour per day in pens stocked at 150% of the stalls versus pens with one cow per stall.
“Lying time was slightly higher still (about 15 minutes per day) when cows were understocked at 75%,” Weary says. He does not suggest stocking densities this low, but it shows even at 100% stocking rate, there is competition for stalls.
That’s because all stalls are not created equal—some are less preferred because they are farther from feed and water or adjacent to solid walls. In yet another study, the least popular stalls were occupied just six hours per day compared to the most popular stalls, which had cows lying in them 15 hours per day. This occurred even though the pen was stocked at one cow per stall.
Keep in mind, too, cows are diurnal, and prefer to lie down together at night. Competition for stalls is therefore greatest at night, so over-stocked pens see the greatest challenges when most farmers are away from the facility.
Note: This story appeared in the September 2017 issue of Dairy Herd Management.
