Tools available to help reduce heat stress in dairy cows

LEWISBURG, Ohio — Reducing heat stress for dairy cows will help to maintain dry matter intake and avoid the loss of milk production.

“The dairy industry in the U.S. loses about $897 million in milk production to heat stress every year,” said Tim Thompson, dairy field technical specialist for Provimi. “We can’t 100% prevent it, but we’re going to do as much as we possibly can to keep our losses at a minimum.”

Thompson advises dairymen to observe their cows.

“Everybody’s conditions are different so you really need to watch your cows and let the cows tell you if they’re hot,” said Thompson during a webinar hosted by Hoard’s Dairyman.

“The easiest way to do that is look at respiration,” Thompson said.

“When the temperature humidity index is under 68, your cows’ respiration rate will typically be under 60,” he explained. “When the respiration rate gets to 61 to 65 respirations per minute, the cow is starting to experience some kind of heat stress.”

One way to help the cows is air movement.

“We need to have air movement over the cows so we’re getting the stale air out in between the cows,” Thompson said. “Air needs to be moving over the cows 4 to 6 mph, but I’ve been in barns where they had too much air because excessive air is not comfortable, either.”

Placement of fans in dairy barns is important.

“More dairymen are using separated solids as bedding and these are very fine particles that can be blown all over,” Thompson said. “If we have the fans blowing down the stall instead of blowing just over the top of the cows, that will blow those particles around for the cows to breathe in and that will make the cows more susceptible to pink eye or pneumonia.”

Water is a cooling factor for dairy cows.

“Under normal conditions cows will drink about three times the dry matter intake and they also need to drink enough water to replace the water lost in milk production,” Thompson said.

“You need about three linear inches of water space per cow for them to drink from and it needs to be clean water,” he stressed. “With heat stress the water intake can go up as much as five times the dry mater intake.”

During summer months, Thompson said, it is a good idea to put a water source in the return alleys.

“Studies show that cattle will drink up to 33% of their needs in the return alleys,” Thompson said. “There needs to be 2 feet of water space for half the parlor so if you have a double 12 then you need 24 feet of water space.”

Adding sprinklers to a dairy barn is beneficial for the cows.

“The combination of fans and water is what really cools the cows,” Thompson said. “Set the sprinklers correctly. Too often they are too high.”

Water should fall on the backs of the cows, where the heat is being created.

“Cows have extremely high metabolism so they’re making a lot of heat and the rumen is a big fermentation vat,” Thompson said. “Anytime we have fermentation we have heat.”

Feeding at night can help cows with heat stress.

“Cows like to eat big meals just before dusk, so during the heat of the day they’re not too excited about getting feed,” Thompson said. “At night we can get cows eating as much as two-thirds of their total intake compared to during the day under heat stress.”

Depending on the forage situation, there are inoculants that can help with bunk life.

“Once the feed starts to warm up that starts depressing dry matter intake,” Thompson said. “At 17 to 20 cents per head per day, you can get a return on investment for a TMR preserver very quickly if your feeds are heating.”

Many heat abatement additives are available and they all help the cow in some form, Thompson said.

“But some are more cost-effective than others and some do a better job than others,” he said.

Vasodilators are organic compounds such as niacin or capsicum.

“They increase the blood flow to the skin and allow the heat to dissipate off the animal,” Thompson said. “Animals will do this naturally, but the vasodilators make it go faster.”

Vasodilators are fed only as needed.

“The con of vasodilators is they have the tendency to decrease the blood flow to the gastrointestinal tract and they also decrease the blood flow to the rumen, but research on these products has not been consistent,” Thompson said.

Electrolytes are positively charged inorganic materials such as sodium and potassium.

“They help to retain the water in the cell to prevent dehydration,” Thompson said. “They help replace losses of sodium in sweat, as well as from milk production.”

Electrolytes are only fed when needed.

“They are a short-term solution and they can’t be fed to dry cows,” Thompson said.

Osmolytes are small organic compounds found in nature that attract water molecules.

“Osmolytes are similar to electrolytes in the way they maintain cell hydration,” Thompson said.

In addition, osmolytes help complement heat shock proteins.

“When an animal gets sick its body temperature goes up because it is trying to destroy the cell proteins in the bacteria or virus to fight off the disease,” Thompson said. “The same thing happens in heat stress, the heat shock proteins try to prevent cellular destruction.”

Osmolytes can be fed to dry cows.

“But they have to be fed proactively to get accumulated protection against heat stress,” Thompson said.

Preventing heat stress is also important for dry cows.

“When it comes to heat, you need to treat dry cows like a lactating herd,” Thompson said. “You got to have shade for them and air movement.”

The dry cows need cool drinking water.

“One inch of linear water space per cow is sufficient,” Thompson said. “They probably need sprinkling of water, but not as intense as lactating cows because these cows are not producing as much heat since they’re not eating as much.”

For more information about products available from Provimi, go to www.provimius.com.