GAINESVILLE, Fla. – June is National Dairy Month and the University of Florida Institute of Food and Agricultural Sciences Dairy Unit is studying ways to get more milk and cheese to your table. But it’s no easy task to keep cows cool enough to produce in the scorching Florida sun.

That’s where researchers with the UF/IFAS Dairy Unit, in Hague, Florida come in. “It is difficult for a dairy cow in a hot environment to meet her full potential for either milk yield or fertility,” said Geoff Dahl, chair of the UF/IFAS animal sciences department. “The physiological adjustments the cow makes to prevent body temperature from rising during heat stress reduce productivity.”

This is especially true for cows in their dry period—cows in late pregnancy or who are not lactating. “These are times when we don’t milk the cows, because for six to eight weeks they don’t produce milk,” Dahl explained.

These cows are usually put out to pasture, and that’s where the trouble comes in, Dahl said. The cows suffer from heat stress and their milk production suffers. Also, the calves developing in utero produce less milk in their lifetimes.

For example, heat-stressed cows lose their appetite, Dahl said. Eating less means the cow is able to lower her internal heat production and regulation of body temperature becomes easier, he said. But, the disadvantage to the producer is that this decreases milk yield.

But dry cows are regenerating mammary tissue to prepare for the next lactation, and that is compromised by heat stress, Dahl said.

“The increase in body temperature that occurs during heat stress can itself limit productivity,” Dahl said. “This is certainly true for fertility because the early embryo in the first one to three days of life is not able to develop when body temperature rises to 104°F (40°C).”

The solution, said Dahl, has been to bring cows into a barn where they can stay cool, especially during summer months. “Even in other states that have relatively mild summers, the heat can still have a significant effect on the cows’ ability to produce milk,” he said.

According to Dahl, recent studies show that dry cows cooled during summer months produce almost a gallon and a half more milk than cows that are not cooled. “The science is there that a cooled cow makes for a more productive cow,” he said.

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By: Beverly James, 352-273-3566, beverlymjames@ufl.edu

Source: Geoff Dahl, 352-392-1981 ext. 221, gdahl@ufl.edu

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