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Pre-Vet 3 > 8C. Adaptations > Flashcards

8C. Adaptations Flashcards

1
Q

What are the three ways livestock gain or lose heat?

A
  1. Conduction
  2. Convection
  3. Radiation
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2
Q

What is conduction? What factors influence the amount of heat lost by conduction? Give an example

A
  • Transfer of heat from objects that touch.
    1. Surface area contact
    2. Temperature gradient
    3. Thermal conductivity of the material
  • A dairy cow lying on cold bedding or a calf resting on warm dry bedding.
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3
Q

What is convection? What factors influence the amount of heat lost by convection? Give an example

A

The flow of heat through air or water.
1. Surface area exposed
2. Wind speed
3. Temperature gradient
A horse standing in a pasture when the air temperature is 10°C and there is a 35 mph wind - which is why they need shelter from the wind -

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4
Q

What is radiation?

A

Transfer of heat from objects that are not touching. Heat moves from warmer to cooler objects so animals can gain or lose heat due to radiation

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5
Q

What factors influence the amount of heat lost by radiation?

A
  1. Body surface area exposed
  2. Nature of surroundings
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6
Q

Explain latent heat loss and the different mechanisms for it

A
  • Animals also lose heat through evaporation - physiological cooling when heat is released through either sweating or panting.
    1. Sweating is an effective cooling process in horses but is marginally effective in cattle, sheep, goats and swine. Poultry don’t have sweat glands
    2. Panting used in livestock and poultry as a form of evaporative cooling and can be used as signs of stress
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7
Q

How do poultry respond to heat

A
  1. Lowering or termination of egg production in layers
  2. Lower growth rates
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8
Q

Summary of this photo

A
  1. Left: heat lost by conduction, convection and radiation all depend on the temperature difference between the cow and surrounding environment
  2. Right: one the air temperature exceeds the cows body temperature, heat loss can only occur by evaporation
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9
Q

What factors influence the amount of heat lost by evaporation?

A
  1. Humidity and temperature
  2. Air speed
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10
Q

In what ways does an animal gain heat?

A
  1. Heat produced by metabolic activities
  2. Skeletal muscle activity - by shivering
  3. Heat increment from digestion - generating heat when digesting feed which is why when they are colder they eat more
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11
Q

List five factors that can change the amount of heat produced by an animal.

A
  1. Activity - 20x increase in heat produced
  2. Shivering - 5x increase in heat produced
  3. Metabolic state - lactating, growing, pregnant animals have higher metabolic rates than animal just maintaining themselves, so they produce more heat
  4. Feed intake - one of the by-products of eating is heat therefore the amount of feed consumed and the type of food consumed affects heat production.
  5. Body reserves - creates heat called non-shivering thermogenesis (fat)
  6. Various hormones - increase metabolic rate so more heat is produced as a by-product of metabolism (ex. thyroid hormones, catecholamines)
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12
Q

What is the thermal neutral zone?

A

The range of ambient temperatures where animal performance and well-being is optimized.

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13
Q

What is the Lower Critical Temperature?

A

The ambient temperature below which the rate of metabolic heat production of a resting, thermo-regulating animal increases by shivering and non-shivering thermogenesis to maintain constant body temperature.
- If it’s below the temp, then it causes cold stress

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14
Q

What is the Upper Critical Temperature?

A

The ambient temperature at which evaporative heat loss by sweating and panting is first detected, and heat production increases due to increased body temperature and the requirements of sweating and panting.
- above this temp - heat stress

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15
Q

What are two important factors that influence thermal zones and critical temperatures?

A
  1. Insulation - more insulation = can lower critical temp
  2. Level of feed intake
  3. Level of activity - more activity, lower critical temp
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16
Q

Describe the optimum zone within the thermal neutral zone.

A
  • It is the range of temperature where optimum productivity, performance, and efficiency is demonstrated.
  • Energy flow to the animal is maximum, and there is no net gain or loss of heat from the animal.
17
Q

Describe the cool zone within the thermal neutral zone.

A
  • Temperature range immediately below the optimum zone, still within the TNZ.
  • Animals show behavioral responses, such as posture adjustment and seeking protection from the wind.
  • Animals make physiological adjustments, including decreasing blood flow to the skin (vasoconstriction).
  • Heat production does not increase.
18
Q

Give some examples of behavioral and physiological changes animals may exhibit in the cool zone.

A
  • Huddling or congregating in areas protected from the elements
  • Chickens fluffing their feathers to create a large space of dead air for insulation
19
Q

Describe the warm zone within the thermal neutral zone.

A
  • Temperature range above the optimum zone, still within the TNZ.
  • Animals exhibit vasodilation to increase blood flow to the skin, decrease feed intake, and change posture to increase heat loss and minimize heat production.
20
Q

Which animals are more susceptible to hot climates due to greater metabolic heat production?

A
  • High-producing animals have greater metabolic heat production, making them more susceptible to hot climates.
  • In contrast, they have an advantage in cold conditions due to their higher heat production.
  • Animals maintain extremity temperature below that of the body through a countercurrent mechanism to avoid excess heat loss.
21
Q

How does insulation and temperature affect intake and maintenance during stress?

A
  • Increased feed intake during stress cannot offset increased maintenance requirements. Insulation (hair, wool, feathers, fat) lowers the lower critical temperature (LCT) and the thermoneutral zone (TNZ) to a lower effective temperature.
  • When heat rises, respiratory rate increases, feed intake decreases (leading to reduced growth).
  • In colder conditions, gut capacity limits feeding, so feed needs to be more nutrient-dense.
22
Q

Example of EET

A

Pig in a group in a closed house where air temperature is 20ºC
(thermoneutral for most growing- finishing swine), air speed at
pig level is 0.5 m/sec, the floor is slatted concrete, and the walls
are on average cooler than the air.
- Air temperature 20C - Minus correction for air speed
- First approximation of EET 13C - Minus correction for floor type
- Second approximation of EET 8C - Minus correction for surface temperature
- EET 6.5C

23
Q

What are the factors that affect EET, LCT and UCT

A
  1. Body size
  2. Metabolic activity of animal
  3. Feed intake
  4. Grouping
  5. Air speed
  6. Humidity
  7. Bedding
  8. Flooring
  9. Availability of sun or shade
24
Q

How does body size affect EET/LCT/UCT?

A
  • Relates to surface area : mass
  • Smaller animals generally have more surface area per kg and thus lose more heat per kg. This means that the smaller
    an animal the higher the LCT and the higher the UCT.
  • This is one of the reasons newborn animals generally have greater heat requirements than older animals.
  • We often deal with this by providing the young animals with a microenvironment (Heat lamps for piglets, chick brooders
    etc.)
25
Q

How does metabolic activity affect EET/LCT/UCT?

A
  • Animals that are growing, exercising, producing milk, growing a fetus etc. will be more metabolically active and as such will have higher rates of heat production.
  • This means they will have lower LCT and lower UCT.
26
Q

How does feed intake affect EET/LCT/UCT?

A
  • In the process of digesting and metabolizing feed animals produce heat as a byproduct.
  • Therefore, the more feed an animal is consuming the greater its heat production, the lower its LCT and the
    lower its UCT.
  • The type of feed and the type of digestive tract also have an
    influence.
  • Ruminants have more heat produced during digestion than do
    monogastrics. This is especially true when feeding roughages.
  • This then is a reason why cattle and sheep have lower LCT and lower UCT then pigs. - More heat is generated from fiber
27
Q

How does grouping affect EET/LCT/UCT?

A
  • When animals are housed in groups it increases their ability to conserve heat and can impair their ability to dissipate heat,
  • Therefore, group housed animals generally have lower LCT and lower UCT than single animals.
  • Animals can huddle together and form “one larger animal” in terms of surface area: provide insulation for eachother,
    heat conserving mechanism
28
Q

How does air speed affect EET/LCT/UCT?

A

Movement of air increases convective heat loss therefore as wind speed increases the LCT rises and the UCT temperature also rises.
- These types of wind speeds can occur from drafts within buildings, especially at ground level. Therefore, the wind
speed within facilities should be monitored.
23
- Obviously, the wind chill factor can greatly influence what environmental temperature cattle can endure during the winter. It thus becomes necessary to provide wind shelters to protect cattle in the winter.
- These shelters can be naturally occurring land formations, fences, shelter belts or even open fronted sheds

29
Q

How does humidity affect EET/LCT/UCT?

A
  • High humidity can result in increased heat loss during cold periods and decreased heat loss during hot periods
    therefore high humidity can increase LCT and decrease UCT.
  • Humidity is also a health concern in confined spaces as high humidity tends to promote the longevity of disease
    organisms, and thus increase the spread of disease.
  • In swine housing we tend to aim for 40-75% RH.
  • For poultry we aim for 50-75% RH.
30
Q

How does bedding affect EET/LCT/UCT?

A
  • The presence or absence of bedding can alter the animals LCT and UCT.
  • Dry bedding can decrease the LCT for all species, and is essential when housing hogs outdoors.
  • Wet bedding loses its ability to insulate.
  • Manure pack can actually generate heat
31
Q

How does flooring affect EET/LCT/UCT?

A
  • Animals can gain or lose heat through conduction to the floors and walls of the environment.
  • Slatted flooring increases heat loss due to convective heat loss and thus raises the LCT of animals.
32
Q

Which type of flooring has the highest/lowest thermal conductivity and insulating value

A

thermal conductivity
H: aluminum
L: still air

insulating value
H: air
L: aluminum

33
Q

How does availability of sun or shade affect EET/LCT/UCT?

A
  • The sun provides radiant heat to animals.
  • Therefore, in the winter we want animals to have access to sunshine and in the summer we want them to have a means of getting out of the direct sunlight.
  • Animal also radiate heat to the environment: Clear cold night cattle move under roof, if
34
Q
A

Pre-Vet 3 (37 decks)

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