Northern cows experience ‘acclimation’ heat stress, angling fans downward helped

kytour-70It’s March, and even in northern climates, those bouts of warm weather and rising humidity are just around the corner. In fact, as warmer days arrive, key research shows it is the acclimation phases that have the most negative impacts, explaining why producers in northern climates tend to report serious impacts from bouts of summer heat stress early (June) and late (September).

During a Dairy Day Program at Miner Institute, West Chazy, New York in December 2019, director of research Katie Ballard presented findings from three summers of North Country study.

“This research has shown us dairy cows are adversely impacted by episodic bouts of heat stress, even during a summer without any true heat waves,” Ballard explains. “We are evaluating various heat abatement measures that farmers can match to their individual farm facilities to help increase cow comfort and maintain milk production during periods of heat stress.”

Ballard explains that it takes weeks for cows to get acclimated to temperature shifts, that even though cows in New York spend an average of only 8% of their year in heat stress compared with the national average of 14%, the acclimation phase can produce significant and costly negative effects.

Bottom line: Cattle recorded 2.5 fewer hours of lying time but had 1.5 more lying bouts during hot days vs. cool days.  This suggests the cows shortened their lying times to stand to cool down before reclining again.

Researchers found that in 2017 and 2018, regardless of the type of heat abatement system in place, the cows on all four farms experienced a pronounced decrease in lying time from the cool days to the hot days and the most dramatic change in lying behavior occurred on the farm using solely natural ventilation as their heat abatement system. All of the herds had fans and sprinklers in the holding area and some of the herds had other heat abatement measures in the barn area.

Ballard noted a striking difference in the 2019 data on one of the farms, a 700-cow dairy, where the owner had changed the angle of the fans by pointing them downward to blow more air directly onto the cows. They also reduced the amount of overcrowding. On both counts, the cows benefited from better air movement, especially in the holding area.

By changing the fan angles to point downward, this dairy showed better performance as a result of receiving better air flow and more cooling effect from the fans that were already in the facility — a low-cost intervention to maximize what the dairy already had in place.

The cows on this dairy had better performance in terms of lameness scores, milk production and components. During the acclimation phases when bouts of higher thermal heat index affected cow lying times on other dairies, the focal cows on this dairy had less change observed in their lying time, despite the hotter nights.


A Northern New York Ag Development Program (NNYADP) grant in 2015 funded the ongoing summer heat stress study as Ballard builds a “climate-adaptability” knowledge base for dairy producers

The researchers worked with the dairy herd at Miner Institute and four participating northern New York farms ranging 300 to 700 cows with different housing systems and heat abatement measures. All herds were high production herds.

Researchers selected 30 “focal” cows in each herd for monitoring. The monitoring included lameness scoring and milk, protein and fat records. Also monitored are activity levels, rectal temps, rumen pH, as well as eating, drinking and lying bouts.

In addition, researchers mounted a livestock heat stress monitor within the pen that calculated and recorded the temperature humidity index (THI) continuously throughout the duration of the summer.

Zahncroft-6631What makes the Miner research unique is that it looks at how cows react to — and are impacted by — heat stress in northern climates linked to acclimation phases as temperature indexes change, which is different from southern climates, where heat stress patterns are ongoing and persistent with fewer so-called “acclimation phases”. Also unique to the multi-year Miner Institute study is the expansion to look specifically at rumen health.

As for the angled fans, experts say the higher the fans are placed above the cows, and the closer they are together, the steeper the angle needed to blow air volume across cows and onto them.

Zahncroft6635(TwilightTour)Other considerations when it comes to fans and placement:

In general, research shows that airflow over a cow with a velocity between 400 and 600 feet per minute will significantly help to maintain cow comfort at temperatures 75 °F and above. When incrementally installing fans in a dairy facility, Cornell ag engineer Curt Gooch suggests these guidelines for the order of importance:

  1. Holding area
  2. Milking area
  3. Close up dry cows
  4. Calving area
  5. Fresh cows
  6. High producers
  7. Low producers

— by Sherry Bunting, compiled from multiple reports

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