PVMA Keystone Veterinarian Summer 2021 - 21

Veterinarians are well aware that major livestock species,
other than horses, don't have a physiologic mechanism such as
sweating to help control their internal temperature. Nighttime
temperatures must fall below 70°F for effective heat dissipation.
Panting is not especially effective at dispersing body heat
when ambient temperatures or humidity are high or following
vigorous exercise. On days of high THI, other means of reducing
heat stress may be very useful.
Management practices, such as feeding the largest part of the
diet for ruminants in the evening; avoiding catching, herding,
or other exercise during the middle of the day; providing ample
access to water; and providing shade, should be promoted. It
is also important to remember on especially hot days animals
may consume twice the volume of water compared to thermoneutral
days. Volumes of water sufficient in April may not be
adequate in July or August. While these interventions may
seem simple and intuitive, not all producers employ practices
to reduce heat stress or are even sensitive to this aspect of
livestock welfare, so reminders from their veterinarian may be
helpful.
Expertise from agricultural engineers can help farmers and
veterinarians better understand and implement strategies
to further lower the impacts of hot weather. One common
acronym used by engineers to address heat stress abatement is
SAAW:
Shade. This seems so fundamental and simple, but it can be
alarming to see many animals on pasture with little or no
shade. Barns may be aligned so that stalls are in the sun for
much of the day. Shade will seem 10 to 15°F cooler due to
the reduction in radiant heat from the sun. Many beef cattle
are now specifically bred to have a black coat, as that can
be a marketing advantage. Imagine being in a pasture with
too little shade for the number of animals. It is little wonder
cattle may crowd together under one or two trees making
mud and increasing fly problems. Livestock panting while
out on pasture is a sign that they are too hot.
Air Exchange. This involves replacing the air, not just
moving it around. This can occur in tunnel-ventilated barns
where whole volumes of air are moved in then out or in
open spaces with gentle breezes. Ideally, hot moist air is
replaced by drier and cooler air. In a barn in cold weather,
air is usually exchanged about 4 times per hour. Increasing
this exchange rate in summer will make animals more
comfortable. Not all open windows, fans, or open vents
actually help to replace air in barns. The nose test can often
help determine if more exchanges are needed.
Air Velocity. In this case, turbulence (at air speeds 3-5 mph
or greater) moves the air close to the body away from the
animal. On pastures or outside pens, animals can crowd
together too closely to benefit from air velocity even if there
are nice breezes and air is being exchanged. In a barn with
fans, air velocity may make animals more comfortable even
if the air is recirculated.
For those who wish to provide information to their
producers, here are helpful references:
1. Heat Stress in Horses: bit.ly/KVM-HeatStress-Horses
2.
Heat Stress in Dairy Cattle: bit.ly/KVM-HeatStress-Dairy
3.
Heat Stress in Swine: bit.ly/KVM-Heat-Stress-Swine
4. Heat Stress in Poultry: bit.ly/KVM-Heat-Stress-Poultry
5. Heat Stress in Small Ruminants: bit.ly/KVM-HeatStress-Ruminants
6.
Heat Stress in Beef Cattle: bit.ly/KVM-Heat-StressBeef-Cattle
Water.
Water has a two-pronged impact on heat stress. First,
livestock may double their water intake when temperatures
are high. The space around, number of, and access to
waterers should be abundant and increased compared to
during times of cooler or cold weather. Producers need
to ensure that water quantity and quality are adequate to
meet the needs of their stock. Second, water can be a very
effective means to directly cool animals via sprinklers or
baths. Due to their hair coat, animals must be soaked for
direct cooling. Livestock with hair coats do not benefit from
misters, as mist on a hair coat may act like insulation and
actually increase heat stress in animals.
Addressing animal welfare deficiencies is an obvious, inferred,
and important role for all veterinarians and veterinary staff. It
is not necessary for producers to allow their animals to suffer
severe disease such as heat exhaustion before veterinary
intervention is necessary. Heat stress impacts on animal health
and productivity can be subtle, yet significant. Teaching owners
and producers to recognize early signs of heat stress and then
employing basic strategies to reduce heat stress can greatly
improve the health and welfare of animals. A more proactive
role by large animal veterinarians can and will improve livestock
health and welfare during the summer months.
About the Author: Dr. Wolfgang practiced veterinary
medicine with an emphasis on large animals from June
1982 through October 1995. From October 1995 through
July 2016, he was the Director of Field Investigations and
Extension Veterinarian with the Department of Veterinary
and Biomedical Sciences at Penn State. In 2016, he
accepted the position as Pennsylvania State Veterinarian.
He retired in 2019; however, is still focusing on providing
his professional experience and knowledge in cost-effective
preventative health and diagnostic programs for livestock
species, as well as farm food safety and quality, emerging
diseases, zoonotic diseases, and overall animal wellbeing.
He can be contacted with questions or comments at
drwolfgang2@comcast.net or 814.574.6848.
Pennsylvania Veterinary Medical Association | 21
http://bit.ly/KVM-Heat- Stress-Horses http://bit.ly/KVM-Heat- Stress-Dairy http://www.bit.ly/KVM-Heat-Stress-Swine http://www.bit.ly/KVM-Heat-Stress-Poultry http://bit.ly/KVM-Heat-Stress-Ruminants http://bit.ly/KVM-Heat-Stress-Beef-Cattle
PVMA Keystone Veterinarian Summer 2021

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