In order to maximize a new or remodeled milking facility, the trick is to size the parlor and cow groups for the most efficient cow throughput without keeping the cow from her usual daily activities.
Every type of parlor – parallel, herringbone, rotary and swing – has a throughput estimate for each size. While those estimates are good for planning, Nigel Cook said we must “assume these numbers are missing something.”
At a Dairyland Initiative workshop in Madison, Wisconsin, in November, Cook (from the University of Wisconsin School of Veterinary Medicine) explained the available throughput estimates are the actual times cows spend in the parlor. It does not include the time cows spend around the parlor in the holding area, exit lanes and transfer lanes.
When trying to rough out parlor size, Cook provided two equations:
number of milking cows / hours per milking shift = desired cows per hour
cows per hour / turns per hour = number of milking stalls
For turns per hour, he said some farms average two while others might be at 5.5. Most consultants suggest planning for 4.5 turns per hour.
An example of the calculation for a 1,000-cow dairy, milking 3X with a seven-hour shift – allowing for a one-hour cleanup after each shift – would result in 143 cows per hour (1,000 / 7). With 4.5 turns per hour, the number of milking stalls needed is 32 (143 / 4.5) or a double-16.
“A double-16 should work, provided you’re doing 4.5 turns per hour,” Cook said. “That’s the big ‘if.’”
Bigger parlors can milk cows faster and support group sizes up to 400 cows. “We can get it done through the technology in the parlor,” he said. “Then we have to have the debate about whether we should.”
A number of other items come into play when considering group size and parlor size; one subject in particular is the holding area.
“Probably my biggest welfare concern after lameness, to be honest, is the holding area right now,” Cook said.
After surveying 66 herds that average more than 90 pounds of milk per cow, he learned the group as a whole averaged only 13.6 square feet per cow in the holding area. The recommended number is 15 to 20 square feet per cow, depending on cow size.
Then if the farm plans to bring the next group up before the first one has left, resulting in more than one group at a time in the holding area, an extra 25 percent space should be factored into the size of the holding area.
“I would rather overbuild this area than underbuild,” Cook said. “Producers always tend to want to add a few more cows. It’s a very limiting design part of the facility.”
Holding area capacity, as well as parlor size and throughput, play a role in determining group size. Other factors include herd size, target days in the pen, calving pattern, time budgets and how the prefresh and hospital pens are managed.
Revisiting the group of 66 herds, Cook said the average herd size was 850 cows. The average time out of the pen – from the first cow out of the pen to the last cow in the pen – was 90 minutes. “That’s pretty long,” he said. “I desire 60.”
The average size parlor was a double-14 and group size averaged 130 cows, which meant an average of 87 cows per hour or 3.1 turns per hour. “Far less than the nirvana, which is 4 to 4.5,” he said.
The goal of arranging parlor size and group size to accommodate only 60 minutes away from the pen has to do with a cow’s time budget for a 24-hour period.
Each day a cow should lie down for 12 hours per day and spend 4.5 hours eating. “That’s non-negotiable,” he said. The more negotiable time in a cow’s day are the two hours standing in the stall and the 2.5 hours standing in the alleyways.
“We can limit the time standing in the stall,” Cook said. “In the best designs, we can actually get it down to maybe 30 to 45 minutes.” However, lame cows will stand longer, and the average is still around two hours.
In the 2.5 hours spent standing in the alleyways, the cows spend 30 minutes around the waterers, 10 of which are actually spent drinking. With drinking removed, there’s two hours left, which could be reduced, but only down to 1.5 hours at best, he suggested.
When added together, there are only three hours left per day for the cow to be milked. If you look at the data, he said, when milking time expands, the cow chooses to reduce her lying time, maintaining the time spent in other behaviors.
“That time milking is really critically important if we’re trying to shoot for 12 hours of rest,” he said.
The three hours for milking includes time out of the pen. It’s not just time in the parlor but also transfer time and time in the holding area.
The normal gait for a cow is 3 feet per second. In the survey of 66 herds, the average distance from the parlor to the pen was 332 feet one way. It would take the cows a minimum of two minutes to get from the pen to the parlor or four to five minutes both ways.
To provide some wiggle room, he suggested doubling that number, leaving only 50 minutes of time in the parlor and holding area.
Therefore, when calculating parlor size, if aiming for 4.5 turns per hour, it should really be 3.8 turns per hour, or 83 percent of the maximum cows milked per hour should be the group size, he said.
This can still result in fairly large groups. A double-20 parlor can handle a group size of 150 cows, a double-30 can milk 228 cows, and a double-50 could do 380 cows.
Even though harvesting milk is an important part of a cow’s day, making sure the parlor and groups are sized accordingly to keep her time away from the pen to just 60 minutes per milking will help her focus on the other task at hand – producing the milk to be harvested. PD
PHOTO: Even though harvesting milk is an important part of a cow’s day, making sure the parlor and groups are sized accordingly to keep her time away from the pen to just 60 minutes per milking will help her focus on the other task at hand – producing the milk to be harvested. Staff photo.
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Karen Lee
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