Friday, May 6, 2016

Cooling Dry Cows?

In a small study done in Florida (n=20) it was demonstrated that heat stress among dry cows may play a role in the growth and development of heifer calves.

Ten dry cows had luxury apartments - their free stall area had fans and soakers. Ten dry cows had the standard housing - no fans, no soakers. The temperature-humidity index in both stall areas averaged 78. (Referring to the standard THI graph, 78 is in the upper end of the "moderate-heat-stress" range. That puts it relatively close to being classified as "severe heat stress.")

The heat-stress cows had higher rectal temperatures compared to cooled cows. Cooled cows had a respiration rate of 49 breaths/minute compared to 67 br/min for heat-stressed cows. Lots of huff and puff for the heat-stressed cows.

What happened to the heifer calves? Although they all started out about similar birth weights by the time they reached 56 days the calves from cooled dams were heavier (157 pounds from cooled dams, 135 pounds from heat-stress dams). 

An analysis of feed intake showed that most of this difference was dry matter intake from calf starter grain. At the end of the 56-day trial cooled-dam calves were eating about 4.4 pounds of grain daily compared with the 3.0 pound-a-day consumption of the heat-stress-dam calves.

Only a small study - but the differences were pretty large. Just one more reason to keep our expectant mothers comfortable.

Reference: A.P.A Monteiro and Others, "Effect of maternal heat stress during the dry period on growth and metabolism of calves." Journal of Dairy Science 99:3896-3907 May 2016.

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