More cows do not necessarily mean more milk

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­When Ken Birker sold off 15 percent of his herd a few years ago, he naturally expected the milk in his bulk tank to go down, at least temporarily. Funny thing is, it never happened.

Dairy cow “We were milking about 400 cows at the time, and made a strategic decision to focus on our better animals and switch to three-times-a-day milking,” the Vinton, Iowa, dairyman explains. “It was our hope that we could eventually return to the same level of production with fewer cows, but certainly did not expect that it would happen so quickly– essentially overnight.”

In retrospect, Birker believes the remaining cows responded to an improvement in stocking density – easier access to feed and water; higher per-cow feed intake; and improved free stall accessibility, which allowed for more hours of rest per day, improved rumination and healthier feet and legs.

His experience is no surprise to Chris Hill, nutritionist for Poulin Grain, Inc., who consults with dairies throughout Vermont’s Champlain Valley. Prior to his current job, Hill managed three dairies and worked on a number of others – some large, some small, and with varying priorities regarding animal behavior and cow comfort. “After working on several dairies, I was impressed by the improvements in herd healh, reproduction and milk production I saw on the farms with excellent cow comfort and stall availability,” he says.

Lessons in cow comfort

Motivated by these observations, Hill returned to graduate school at the University of Vermont and chose to place his research emphasis on stocking density and animal behavior. His trial work was conducted at the nearby Miner Institute at Chazy, N.Y., where he collaborated with Peter Krawczel, PhD, who is now in the Department of Animal Science at the University of Tennessee.

Both researchers attempted to identify the ideal stocking density that would allow cows to behave naturally, for the best possible health and productivity outcomes. Among the results they found were:

1. Cows will choose rest over eating. Cows need between 10 and 14 hours of resting time per day, and three to five hours for eating. The remainder of the time is allocated to travelling to and from the parlor; milking; drinking water; grooming; social behavior and estrous activity. But they prefer rest over all other behaviors, and if adequate resting space is not available, they will sacrifice time for other activities to rest when they can. Krawczel cites a study that also showed an increase in the level of the stress hormone cortisol, and a decrease in growth hormone, in cows that were deprived of adequate resting time. And, in their work at the Miner Institute, they found an advantage of 3.7 pounds of milk per day for each extra hour of resting time that cows received. “It is a fallacy that if cows aren’t lying down it is a good thing, because that must mean they are up and eating,” says Hill. “I’ve spent a lot of time observing cows at all hours of the day and night, and too often we see cows just standing around doing nothing. They are interested in resting, not eating, but they cannot find the space to lie down. They simply run out of hours in the day to get it all done.”

2. Overstocking can cause an illusion of good stall comfort. Cows will use virtually any stall if they are forced to do so, but that doesn’t mean they enjoy it. University of British Columbia (UBC) research showed that standing versus lying time is longer in uncomfortable stalls. In other words, cows will climb right in, lie down and stay down in comfortable stalls, but will stand longer if they are uncomfortable. Another sign of discomfort is a high incidence of cows “perching” with two feet in a stall – whether occupied or unoccupied by another cow. Krawczel says researchers at the UBC found that cows would use less-preferred stalls more frequently when preferred stalls were blocked, indicating that it was a “forced” choice. For this reason, Hill feels that the Stall Use Index (SUI) provides a better assessment of comfort in overcrowded situations than either the Cow Comfort (CCI) or Stall Standing Indices (SSI) because SUI acccounts for all cows in the pen that are not eating and not just those occupying a stall.

3. Bedding and stall maintenance matter. Excellent bedding and stall maintenance can compensate for many other imperfections, including small stalls. Hill says a deep, clean, inviting surface will encourage cows to readily lie down. The type of bedding matters, too. UBC research found a 23.8 percent incidence of hock lesions when sand bedding was used, compared to 69.7 percent with sawdust and 91.7 percent with mattresses. Numerous mastitis studies also have shown a lower incidence of environmental mastitis with sand bedding compared to organic materials. Hill says sand usually is less expensive and more available than other types of bedding. He adds that he has seen farms develop a number of creative ways to keep sand out of the mechanics of manure removal equipment, which is often a factor that creates reluctance to use sand. “I tell people, you can break your manure equipment, or you can break your cows,” advises Hill. “A machine can’t feel pain and discomfort, but the cows definitely can.”

4. Feeding behavior is affected, too. Cows have a tremendous propensity to eat, and overstocking at the feedbunk can drive cows to the point of physical injury. Research has shown that cows will willingly exert more than 500 pounds of pressure against the feed barrier while eating. Tissue damage occurs at 225 pounds of pressure, meaning that cows can permanently wear the scars of overcrowding at the bunk. “When you walk onto a farm and see cows with massive calluses on their necks, it is more likely to be a feed bunk push-up or design problem than a stall problem,” says Hill.

5. Heifers and lame cows will suffer first. Natural animal behavior dictates that dominant animals will gain more ready access to stalls. In Hill’s research, he found that milk production started to drop in first-calf heifers mixed with older cows when they were just 15 percent overstocked. He found that lame cows started to lose production at the same threshold of 15 percent overstocking when mixed with healthy cows.

It depends…

So what is the ideal stocking density? “Unfortunately, there is no ‘magic number,’” says Krawczel. “It really comes down to adjusting up and down from your current level.” Barn design, stall design, 2X or 3X milking, location of waterers, weather, bedding and a host of other factors have bearing on the decision, he says, noting that 120 percent is a reasonable number to work around in many cases.

At the Birker Dairy in Iowa, they have arrived at a stocking density of 120 percent for first-calf heifers and 112 percent for higher-parity cows. Ken Birker adds that those numbers always are fluid, and are regularly re-evaluated based on current weather, feed and cow health conditions.”

Hill says his experience has shown that stocking density is intricately linked to virtually every aspect of cow health and performance – milk production; udder health and milk quality; fresh-cow health; foot and leg health; estrus expression and reproductive efficiency, and more. Less-than-optimal results in any of those areas could be linked to overstocking.

For example, “a lot of people try switching to 3X milking and are disappointed that they don’t see much of a response,” shares Hill. “The reason could be that the herd’s stocking density is too high, and then they are asking even more of their cows. The cows get even less rest, and they just can’t respond with higher production. I firmly believe the most successful dairies are the ones that make their decisions based on what is best for the cow,” he says. “If the cows are comfortable and healthy, everybody wins.”

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Ohio  |  February, 05, 2013 at 03:32 PM

I cannot believe 120% is your number. Anytime we get over 110% we suffer in the tank. We will get same amount in tank at 108% as we do at 115%.

Chris Hill    
Vermont  |  February, 05, 2013 at 09:18 PM

Twenty percent over is a starting point and average for the whole farm. Some farms successfully maintain levels higher than this, but they almost always have everything else just about perfect. I think there are many other farms running at this level or higher who think they are doing fine that would actually benefit from making adjustments like you have. Many factors influence how cows respond to increased levels of overcrowding. Transition cows, heifers mixed with mature cows, and lame cows all have trouble competing for limited resources. There is plenty of research showing these cows will be impacted by stocking rates above 100%. Uncomfortable stalls and long holding area or lock-up times prevent cows from lying down. Even though mature, healthy cows may perform fine at 120-130% stocking rates in ideal situations, anything limiting lying time to these cows will also limit the ability to successfully overcrowd these cows. Ultimately, each farmer should determine the ideal stocking rate not only for the farm as a whole, but also for different pens on the farm. Observing and measuring behavior and performance as crowding levels grow could be a real eye-opener in many situations.

Mike Van Amburgh    
NY  |  February, 07, 2013 at 09:28 AM

You have to consider the barn design. If you are a 6 row barn, the feedbunk is already 20-30% overcrowded compared to a 4 row barn with no stall overcrowding. So the amount of overcrowding at the feedbunk does not parallel the amount of overcrowding at the stall level among barns and that will affect how the Miner data is applied.

Chris Hill    
Vermont  |  February, 07, 2013 at 02:13 PM

Mike is correct. The studies done at Miner to date have matched the number of headlocks available to the number of stalls. Although stall availability appears to be more limiting than bunk space, there is good research primarily from Wisconsin, showing negative impacts on fresh cow health and performance when prefresh and fresh cows are overcrowded at the bunk. Cows also tend to eat fewer, shorter meals and therefore slugfeed to maintain intake levels when bunk space is limited. One NY study found decreased cud chewing and my study at Miner found reduced butterfat as cows became more crowded.

Robin Rastani    
Wisconsin  |  February, 11, 2013 at 07:50 AM

Mike and Chris bring up some great points. I think the amount of overcrowding a facility can handle has to do with a number of factors, including barn design (4 row vs. 6 row, cow flow, pen size), size of the cows, how much time they are out of the pen and the overall management. Some managers can handle 120% stocking density in their facilities with their cows and system, while others lose milk at this stocking rate. As with any benchmark, it's simply a level that seems to work in some situations, and needs to be adjusted based on performance at each individual farm.

name with held    
lowa  |  March, 01, 2013 at 12:32 PM

I guess I would like to know how Mr birker got his info. Mr birker has had little to do with day to day operations of his dairy for the past 20 yrs. Other than going to board meetings and playing the part of owner. The credit should go to his employees who have been taken for granted for so long. And under paid and over worked. It takes someone to be there everyday. Not when the cameras are rolling. Thank you for your time and your welcome.

with held    
iowa  |  March, 09, 2013 at 09:34 PM

I say I won't have to agree. I know the real mind behind birker inc. He put his life and love on the line for that farm to be treated like a nobody when the cameras showed up. But family who had said the dairy was a waste of time and money off camera. HOW SAD . Now the dairy sufferers. Except when they are off at so called meetings. They really know who gets credit for taking a 16000 rha to 27000 rha. In a 10 yr time.

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