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LONE ROCK, Wis. - Profitable cows stay in a milking herd more than two lactations. But to do that, they must also be healthy cows.
"Making sure profitable cows stay profitable beyond their second lactations has a positive economic impact on the net returns of a dairy farm," said livestock specialist Dave Meidl, during the recent Midwestern Bio-Ag field day, on Otter Creek Organic Farms, near Lone Rock, Wis. He and fellow livestock specialist Jon Woolever noted that keeping a cow milking more than two lactations spreads out all the costs associated with raising, feeding and managing her.
Trouble is, the average dairy cow stays in a herd less than two years, Meidl said. That quick turnover costs money.
It's important to keep a farm's culling rate below 35 percent, he said. If it rises to 40 percent, a farm loses approximately $10,000 a year. Conversely, Meidl said, "Decreasing the culling rate by five percent can increase the profitability of a dairy 15 to 20 cents per hundredweight" of milk sold.
In terms of numbers, a cow that has been milking two lactations has produced gross income of $6,832. But keep her for six lactations and she has grossed $20,496, said Meidl. Those numbers assume milk worth $16 per hundredweight, a cow averaging 70 pounds of milk a day, and a 305-day lactation.
Most cows, according to Meidl, are not really profitable until they've been milking more than 30 months. That means it's vital to lower the involuntary culling rate, so a cow exits the herd when the dairy producer wants her to - not when she has a health problem that forces her out.
Those health problems mainly relate to the udders, lameness, some sort of injury, or a reproductive ailment. Roughly 65 percent of cows are culled for those reasons.
"You want to make the culling decisions on your farm and not have the cows make them for you," Meidl said.

Comfort, health
Two main aspects of cow management are critical: comfort and health. Under cow comfort, Meidl listed proper housing, feed availability and reducing heat stress. As for cow health, he included managing lameness, minimizing problems with transition cows, and providing plenty of water and a balanced ration.
Stall sizes and designs sometimes need changing.
"Maybe the stalls are too small, because the herd's genetic makeup has changed and the cows are now tipping the scales nearer 1,500 pounds than 1,200," Meidl said.
A rule of thumb is building stalls eight to nine feet long, or 16 feet long for two stalls that are laid out alley to alley. If a stall meets a wall, 10 feet total should be enough. The width can vary from 54 to 60 inches, depending on whether a cow weighs 1,400, 1,600 or 1,800 pounds. Build stalls too small, and hock sores and stepped-on teats can result, Meidl said.
Bedded packs need to be big enough, too. Meidl suggested at least 85 square feet per cow.
To encourage cows to rest at least 12 hours a day, stalls need to be comfortable, and there needs to be enough of them, said Woolever. A dairy cow carries 400 or more pounds on each hoof, so she needs to be able to lie down, chew her cud, and rest.
A stocking rate of less than 100 percent is "ideal" for transition cows, said Woolever. That means providing at least one stall per cow.
For lactating cows, a stocking rate of 100 to 115 percent can work. He said one farm reduced its stocking rate from 135 percent and ended up not only cutting the time spent milking, but also sold more milk.
As for feed, make sure it's free of mold and mycotoxins. They can "really ruin herd health," Woolever said.
Make sure the feedbunks are never empty. They should contain feed "23.5 hours a day," which will give timid cows a chance to eat, he said. And, provide at least three feet of bunk space per cow.

Heat stress
Heat stress can take a toll on both cow health and longevity. The keys to combating heat stress, according to Meidl and Woolever, are water, shade and moving air.
Dairy cows do best in temperatures of 35 to 55 degrees Fahrenheit, said Woolever. That means a temperature-humidity index of 70 can cause mild stress.
Cows create plenty of heat on their own, too.
"A cow's rumen is a giant fermentation vat," Woolever said.
Signs of heat stress include eating less, moving less, and drinking more. Heat-stressed cows will also seek shade and breathe rapidly. A cow that's taking 80 to 100 breaths per minute is "very stressed," Woolever said.
A cow under that kind of stress will probably eat 10 percent less than normal, and will also fall 10 percent in milk production. That, said Woolever, is because more of her blood is being shunted to her skin, for cooling, and less is going to her digestive system and udder.
Shade can help with cow cooling. Provide at least 38 to 48 feet of shade per cow, and place the shading structure at least 14 feet off the ground. Use solid shade cloth and run it north to south.
Fans and sprinklers are tools to fight heat stress. A fan needs to move at least 1,000 cubic feet of air per minute to cool one cow, Meidl said.
Thirty-six-inch-diameter fans should be rated at 10,000 cubic feet per minute (cfm), while those 48 inches in diameter should be able to move 20,000 cfm. Place 36-inch fans 20 to 24 feet apart, and mount 48-inch fans 36 to 40 feet apart. Install fans 7.5 to 8.5 feet off the floor and angle them downward at 15 to 20 degrees.
Don't, said Meidl, make the mistake of switching fans off at night, just because conditions have cooled a bit.
"It's important to remember that a cow's body temperature is still going up at night," he said.
For more cooling power, add sprinklers that deliver water droplets at 20 to 30 pounds per square inch. In holding pens, equip sprinklers that deliver water in a full circle. Place these sprinklers four to five feet from the edges of the pen, and eight to 10 feet on center.
Near feedbunks, use 180-degree nozzles, so the feed does not get wet, said Meidl. These sprinklers should be six to eight feet apart and five to seven feet above the floor.
When heat stress is mild, run the sprinklers one to three minutes, with a 15-minute shut off time, Meidl said. With moderate heat stress conditions, shorten the shut off time to 10 minutes, and in conditions of severe heat stress, set the sprinklers so they are off only five minutes. In all conditions, set sprinklers and fans to come on at just above 70 degrees.
In times of heat stress, Meidl said, a cow needs to drink 1.2 to two times as much water as normal. He advised placing waterers along exit lanes from milking parlors, since cows will drink as much 30 percent of their daily intake right after they're milked. Provide two to three linear feet of waterer per cow, and install two waterers per group.

Watch for lameness
Meidl and Woolever also suggested watching carefully for lame cows. Lame cows don't want to walk much, so that affects their ability to get to feed and water.
A study in Michigan found that farmers rated just four percent of 1,300 cows they observed as lame. By contrast, veterinarians said 52 percent of those cows suffered from some degree of lameness.

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