Heat stress can steal profits from dairy producers.

When the temperature rises above 80 degrees F, a cow's body adjusts by dissipating heat through faster heart rate, panting, sweating and dilation of surface blood vessels. This causes the cow's energy maintenance requirement to go up. For example, when the temperature reaches 95 degrees F, the cow requires 20% more energy, which can equate to six pounds of milk per day.

In addition, the cow produces heat when she eats and digests her food--especially with diets high in fiber. As the animal copes with heat, she often reduces feed intake. This reduces heat the cow has to dissipate, but it also means she won't meet her higher energy requirements.

"Milk yield can drop by as much as l9%, robbing the producers' bottom line," says Bill Kautz, DVM, director of technical services for Chr. Hansen. "Over the entire lactation, milk losses can reach 1,200 pounds or more. Long-term effects of heat stress can include reproductive problems and laminitis."

Kautz suggests that producers can use a number of key management and nutritional practices to help reduce heat stress in the dairy herd:

--Provide shade to minimize exposure to environmental heat.

--Use fans or sprinklers to increase heat transfer from cows.

--Provide plenty of cool, clean water.

--Feed very early in the morning, so the maximum heat of digestion, which happens four to five hours after feeding, occurs before the peak daily temperature.

--Feed more often in smaller amounts, so dissipated heat is less and more spread out over the day.

--Feed more frequently to reduce bunk spoilage.

--Feed high quality, palatable forages; poor quality forages create more heat during digestion and are less palatable.

--Use a microbial silage inoculant to help improve forage quality.

--Increase energy density of the ration.

--Increase crude protein and undegradable protein.

--Increase levels of potassium, sodium, phosphorus and magnesium.

Another tool that can help cows through summer's heat is to supplement the ration with a direct-fed microbial (DFM). Research has shown that this can enhance feed intake and digestion, which can help maintain milk production. In a Rutgers University research trial, cows fed Biomate Yeast Plus--a concentrated, live yeast product--ate 2.5 pound more dry matter and produced over 5.7 pounds more milk per head per day.

In addition, field trials involving more than 600 dairy cows have shown positive effects on milk yield and dry matter intake, when cows were given Probios microbial products. Probios is a direct-fed microbial available in gel, granules and water-soluble powder.

"Although we can't turn down the heat, there are many ways that producers can manage their herds to help reduce the overall impact of heat stress," Kautz concludes.

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