Lactating dairy cattle were used to evaluate
three different cooling systems. Eight
cows were arranged in a replicated Latinsquare
design and assigned to each of four
treatments. Treatments were control, lowpressure
soaking (LPS), high-pressure misting
with 1.7 gallons per minute of water (HP-1.7),
or high-pressure misting with 3.4 gallons per
minute of water (HP-3.4). Cows were allowed
to become heat stressed in a free-stall facility,
and then were moved to a tie-stall barn for 2
hours of observations during four hot and humid
afternoons. Respiration rates declined
when heat abatement systems were used.
Respiration rates at the end of the observation
period were reduced by 20, 36, and 48% for
HP-1.7, HP-3.4, and LPS, respectively. Rearudder
skin surface temperature was reduced at
a faster rate under the HP-4 treatment than
with LPS, but the two treatments did not differ
in final rear-udder skin surface temperature
or vaginal temperature. The HP-3.4 treatment
used the greatest amount of water during the
2-hour testing period. The result was a combination
of air-cooling and soaking. Results
indicated that a combination of air cooling and
soaking may result in faster reduction of surface
temperature. When only air cooling was
used (HP-1.7), heat stress was reduced, but it
was less effective than either LPS or HP-3.4.
Use of a low-pressure soaking system is superior
to high-pressure misting unless cattle become
soaked by the high-pressure system.
