Even Short Term, Heat Stress Can Be Costly

Heat stress can have significant effects on both milk volume and component production. ( Farm Journal, Inc. )

As much of the country now enters the dog days of summer, heat stress and its impact on milk production comes front and center.

Just how much it can cost your farm takes some diving into. Checking and comparing monthly Dairy Herd Improvement Association (DHIA) is one way to do it. But taking the bulk tank milk weights at each pick-up along with the number of cows going into the tank is a more accurate approach to monitoring production, says Virginia Ishler, an Extension dairy specialist with Pennsylvania State University.

“This can detect problems earlier and allow for faster solutions to correct heat stress,” she says.

Last year, a 200-cow Pennsylvania herd with minimal heat abatement compared daily milk production from January through May, and then again from June through September. In the first 5 months, the herd averaged 77 lb/cow/day; in the second, the tank average dropped to 70 lb. Based on an average price of $18.83/cwt during the summer months, the lost production cost the farm about $34,000.

Milk fat and protein levels for the herd from the DHIA Summary Sheet were also compared to milk check levels June through September. The milk fat levels from DHIA showed an average of a 3.6 percent fat test for the three months. The milk check fat test, however, averaged 3.504%. DHIA protein averaged 3.05 while the milk check protein averaged 3.013.

“Using the milk check information to document heat stress provided a better assessment of what was happening in the herd,” Ishler says.

When these differences were multiplied by Federal Order #1 component prices for the 4 months, an additional $6,400 was not realized , she adds.

There are two lesson here, says Ishler. First, herds without heat abatement can suffer both production and component reductions during the summer and fall. Second, if DHIA test day data matches the milk check, then drilling down into various performance areas on the DHIA sheets can be beneficial. But if there is too much discrepancy, it may be more difficult to determine which production group is causing the problem.

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