Download ENVIRONMENT & ANIMAL HEALTH

ENVIRONMENT & ANIMAL
HEALTH
by
David R. Hawkins
Michigan State University
An animal’s ability to express its
genetic potential is impacted by
the environment in which it exists.
HOMEOTHERMS
• Farm animals and humans are classified as
homeotherms since they maintain a constant
core body temperature across a wide range
of environments.
• Poikilotherms (cold blooded animals such
as fish and snakes) do not maintain a
constant body temperature, but rather are
influenced by the environment.
NORMAL RECTAL BODY
TEMPERATURE (o F)
•
•
•
•
•
Cattle (100.4 – 102.8)
Sheep (100.9 – 103.8)
Swine (101.6 – 103.6)
Horse (99.1 – 100.8)
Chicken (105.0 – 109.4)
av. 101.5
av. 102.3
av. 102.5
av. 100.0
av. 107.1
SEASONAL CHANGES IN
ENVIRONMENT
• In temperate climates, as seasons change,
ambient temperature and photoperiod
(length of daylight) also change.
• In spring, both temperature and day length
increase.
• In fall, both temperature and day length
decrease.
• Hormonal changes help the animals adapt.
Basal Metabolic Rate
• The thyroid gland near the trachea controls
basal metabolic rate (BMR). As cool air is
inspired, thyroxine secretion increases and
BMR increases heat production.
• Hair growth and shedding are also
influenced by hormones.
THERMONEUTRAL ZONE
• The thermoneutral zone (TNZ) or comfort zone is
a range of environmental temperatures where heat
production and heat loss from the body are about
the same.
• When ambient temperatures drop below the TNZ,
animals increase feed intake and reduce blood
flow to body extremities. Mammals generate heat
by shivering. Birds fluff their feathers to increase
insulation space around their bodies.
THERMONEUTRAL ZONE
• When ambient temperature rises above the
TNZ, water consumption increases,
respiration rate increases and if the animal
can sweat, perspiration increases.
Evaporation of sweat results in cooling.
Effect of Temperature on Feed
Intake, Maintenance & Gain
BASIC MECHANISMS OF
HEAT LOSS OR GAIN
• Conduction is a flow of heat between
objects that are touching.
– A pig laying on a cold concrete floor loses heat
by conduction.
• Radiation is an exchange of heat between
objects not touching.
– Animals absorb heat from the sun and lose heat
in cool shade.
BASIC MECHANISMS OF
HEAT LOSS OR GAIN
• Convection is influenced by body surface
area, air movement, body temperature and
air temperature.
• Evaporation – Animals that can sweat, lose
heat from the surface of their skin.
• All animals vaporize moisture and heat via
respiration.
COLD STRESS
• Wind chill is a function of ambient
temperature and wind speed.
• Heat increment can help offset cold.
• Warm food such as milk to newborn
increases body temperature.
• Animals crowd together to keep warm.
HEAT STRESS
• High ambient temperatures cause decreases
in feed intake, growth rate, milk production
and reproduction (higher embryonic
mortality and reduced sperm production).
• With severe heat stress, central nervous
system is affected and animal may die.
VENTILATION
• In confinement facilities for livestock, it is
important to remove dust, ammonia and
other odors as well as to provide fresh air.
• If humidity builds up in a confinement
building, respiratory problems increase and
production declines.
HEALTH DEFINITIONS
• Mortality = Death Loss
• Morbidity = Sickness
• Disease = Any deviation from normal health
that results in physiological, anatomical or
chemical changes in the animal’s body.
• Diseases may be either infectious or
noninfectious.
HEALTH DEFINITIONS
• Infectious diseases are caused by
microoganisms such as bacteria, viruses and
protozoa.
• A contagious disease is an infectious
disease that spreads rapidly from one
animal to another.
• Noninfectious diseases include nutritional
deficiencies, toxicities, etc.
DISEASE PREVENTION
• Biosecurity will be a major issue in the
future.
• Isolation and testing of new animals before
they enter the herd or flock.
• Restricting visitors and vehicles to farms.
• Sanitation is the first line of defense.
• A herd health program planned with your
veterinarian is critical.
DISEASE PREVENTION &
TREATMENT
• Biologicals are used to prevent diseases.
– Vaccines
• Pharmaceuticals are used to treat diseases.
• Selection of injection sites are critical.
• Employees must be trained regarding early
disease detection and treatment protocol.
DISEASE DETECTION
• Know normal vital signs
– Body Temperature
– Respiration Rate
– Heart Rate
• Recognize abnormal behavior
– Loss of appetite
– Abnormal respiration
– Listlessness and depression