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Using indices to assess freestall comfort

PD Editor Dario Martinez Published on 27 June 2012

A cow’s comfort level affects her health, productivity and performance if not assessed routinely over time. How are you gauging the comfort level of your cows, especially when it comes to the farm’s cow housing environment, particularly freestalls?

“We all understand the importance of cow comfort,” Rick Grant, president of the William H. Miner Agricultural Research Institute, says. “There’s nothing more important to the cow’s comfort in terms of her environment than her lying surface.”

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There are several indices currently used to determine how comfortable the animals are in relation to their housing environment. Grant points out that three of the principal indices are the cow comfort index, the stall standing index and the stall use index.

In addition to consultants and nutritionists, Grant recommends producers take part in monitoring these indices. “The farmer should be very aware of the indices because they are a good signal as to whether or not their stalls are well designed and comfortable to the point where cows are using them,” he says.

Cow Comfort Index
The Cow Comfort Index (CCI) determines the proportion of cows in contact with a stall that are lying down. Grant explains that out of the three indices, this one is the most commonly used. “It was developed in the ’90s but, throughout the last 10 to 20 years, people have used it quite extensively,” he adds.

The CCI is calculated by dividing the total number of cows lying in a stall by the total number of cows in contact with a stall. Grant explains that the phrase ‘in contact with a stall’ is interpreted to mean that the cows are actively in contact with the stall, either lying in or standing with two or four feet of the stall. The benchmark for this index in a well-managed system is 85 percent or more, he says.

An advantage of the CCI is that it estimates the motivation of cows to enter a freestall and lie down. On the other hand, a disadvantage of the index is that it does not measure the amount of time a cow spends lying down.

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Grant adds that a study conducted by researchers at the University of British Columbia in Canada measured CCIs on several farms while also monitoring the cows’ resting activity (lying down time) in a 24-hour period. “The study found that there is little correlation between the cow comfort index and how many hours a day a cow lies in the stall,” Grant says.

He explains that even though the CCI is only a snapshot, it is a very useful one and a starting point in gauging the comfort of the stall. He also advises that these indices should be measured more than just one time in order to obtain more accurate results.

“If you have a higher number, that means that the stalls are well designed and comfortable to the cow, and then you presume that because they are comfortable to the cows, they are getting adequate rest,” Grant says.

Stall Standing Index
The Stall Standing Index (SSI), developed by researchers from the University of Wisconsin’s School of Veterinary Medicine , determines the proportion of cows in contact with a stall that are standing.

To calculate the SSI, the total number of cows standing within a stall is divided the total number of cows lying or standing with two to four feet within a stall, which is the inverse of CCI.

This index, which is not as commonly used as the CCI, helps assess a cow’s standing time. Excessive standing time is normally associated with higher incidences of lameness and other related health and productive issues.

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Grant explains that a well-managed herd ought to have a SSI of less than 15 percent and for sure less than 20 percent.

“A higher SSI is actually associated with a greater daily standing time, so from that perspective it’s a pretty useful tool,” Grant says. “When you see 30 to 40 percent of the cows standing in the stall, that’s a pretty good indicator that you have excessive standing time.”

Grant explains that if cows are perching, in addition to the standing time, they are also not using their stalls correctly. “This provides a clue signaling something could be wrong with the stall design or that there is something in the cow’s stall environment encouraging her to perch rather than lie down,” he says.

Stall Use Index
Grant points out that the Stall Use Index (SUI), developed by University of California – Davis, has not been used as often as the other indices, even though it has been around since 2003. As opposed to the other indices, the SUI places a specific focus in situations where pens are overcrowded.

“We did some research here at the Miner Institute a few years ago and compared all three of the indices,” Grant says. “They’re all useful, but if you really want to gauge the overall effect on a cow’s well being by not just the stall but the fact that she is overcrowded, we found that the Stall Use Index is especially useful.”

With the SUI, the number of cows lying down is calculated and dividing by all the cows in the pen minus the cows that are eating. “What you are doing is factoring out the cows that are productively using their time so that even if they are not lying down, at least they are not wasting their time,” Grant says.

He explains that removing these cows from the equation creates a scenario where the number of cows lying down in the stalls is divided by the number of cows that are wasting their time standing around.

Grant says the SUI is useful in these situations because the cows that are standing are usually waiting for a stall to open up. The benchmark for the SUI in well-managed herds is usually 75 percent or greater, he says.

“Our research shows that the SUI begins to go down remarkably at a stocking density of 120 or 130 percent or more on a stall basis,” he says. “As the stocking density goes up, the SUI goes down.”

Other significant factors
There are other factors that play a role in the outcome of the index measurements. The time of day in which the measurements are taken is one of these factors. “The key is that you have to take your snapshot or scan of the herd at a time when the cows are highly motivated to lie down,” Grant says.

What he means by this is that because cows are on different feeding and milking schedules across different dairies, adjustments should be made so the measurements are taken when cows are most likely to lie down and rest. “It’s recommended to do this one to two hours after the cows return from the parlor or at least two hours before exiting to the parlor,“ he says.

A potential slant in measurements could also occur when indices are assessed at different times of the year, such as the summer months. Grant explains that, with heat stress being a factor, there will be a lower CCI because more cows are going to be standing, but not necessarily because the stalls are uncomfortable.

“Cows do stand up much more when they are heat-stressed because they are trying to create more surface area to dissipate heat and lower their body temperature,” Grant says. “The stalls could be just as comfortable as they were in February but the cows are not using the stalls as much now because they are heat-stressed.”

The setup and amount of ventilation available to the cows are other factors that can affect index measurements.

Although dairy producers do not use these indices widely, Grant points out that the indices will help them better assess the comfort of their freestalls. However, he does point out that using these indices does not replace the detailed analysis of stall design. PD

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