Thermoneutral zone, lower critical temperature, and upper critical temperature, and how they relate to metabolic rate

Question 1

when the animal doesn’t have to expend energy to maintain its normal body temperature.

Answer 1

thermoneutral zone (TNZ)

Question 2

occurs when an animal is exposed to weather conditions that put it below its lower critical temperature.

Answer 2

Cold stress (lower critical temperature)

Question 3

is the opposite of cold stress and occurs when cattle have to expend energy to get rid of body heat to maintain core body temperature.

Answer 3

Heat stress (upper critical temperature)

Question 4

Maintaining the thermoneutral zone can be influenced by several factors:

Answer 4

• the body condition of the animal;
• the type of hair coat (winter versus summer hair and all variations in between);
• whether the hair coat is wet, dry, or muddy; and
• pigmentation of the hide and hair.

Question 5

Climatic Factors :

Answer 5

• Temperature
• Relative humidity
• Air composition
• Air speed and air movement
• Light

Question 6

The highest and lowest critical temperature depend very much on:

Answer 6

1. Age
2. Body weight
3. Housing system
4. Feeding level
5. Relative humidity
6. Air velocity
7. Health

Question 7

if birds have a layer of subcutaneous fat, they can afford to let their skin temperature drop.

Answer 7

Tissue insulation

Question 8

have an insulating effect and decrease the amount of heat that is lost to the environment.

Answer 8

Feathers

Question 9

birds can effectively regulate heat loss through body position. Heat loss can be minimised by huddling close together.

Answer 9

changing body position and huddling

Question 10

if temperatures are high, or extremely high, sensible heat loss is minimised and almost all heat will have to be lost as insensible (latent) heat.

Answer 10

Vaporisation of water

Question 11

the flow of blood to the skin and mucous membranes can be controlled through the contraction and widening of blood vessels.

Answer 11

Flow of blood through skin and mucous membranes

Question 12

Obvious indicators of unsatisfactory house climate are:

Answer 12

• Behaviour of the animals
• Abnormal body position
• External abnormalities
• Abnormal plumage may point to mistakes in house climate
• Coughing/sneezing frequencies
• Activeness

Question 13

several ways of measuring the temperature:

Answer 13

1. Minimum/maximum thermometer (in every house or section of a house)
2. Temperature sensor (computerised climate control)
3. Thermometers (alcohol, electronic)
4. Infrared thermometers – electronic thermometers

Question 14

The carbon dioxide in poultry houses largely originates from air exhaled by the birds.

Answer 14

Carbon dioxide (CO2)

Question 15

is a product of bacteriological processes in the manure. It is easily bound to water.

Answer 15

Ammonia (NH3)

Question 16

is released when organic matter (protein) in the manure decomposes. It has an offensive smell (rotten eggs) and is a very dangerous gas.

Answer 16

Hydrogen sulphide (H2S)

Question 17

is an odourless, very dangerous gas. It is the result of incomplete combustion due to a lack of oxygen (O2) in gas heaters (clean filters).

Answer 17

Carbon monoxide (CO)

Question 18

develops when oil is used as fuel. The cleaner the oil, the less SO2 is formed.

Answer 18

Sulphur dioxide (SO2)