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List some reasons why we house animals
- Control of diet
- Rest pasture - allow grass time to grow
- Parasite control
- Ease of management
- Control of the environment
- Increase output from pasture
What are a housing systems requirements? (10)
- Contain stock
- Provide shelter
- Provide a dry comfortable lying and loafing area
- Provide suitable nutrition
- Remove excess moisture
- Remove noxious gases
- Maintain appropriate temperature ranges
- Separate animals from faecal matter/urine
- Manage the pathogen load
- Provide a safe working environment for people
What factors can affect the thermal comfort of an animal?
- Air temperature
- Moisture content of atmosphere
- Work being done e.g. lactating cow vs newborn calf
Describe the concept of environmental temperature zones for livestock (including upper/lower critical temperature, thermoneutral zone and thermocritical zone)
The thermoneutral zone is when animals are not expending energy trying to gain or lose heat. This zone can be further broken down into a thermocomfort zone which optimises the animals hormones. Below the lower critical temperature an animal will expend energy trying to keep itself warm. Above the upper critical temperature an animal will undergo heat stress and expend energy trying to lose heat.
What is the upper and lower critical temperatures for a 15kg piglet?
What is the upper and lower critical temperatures for a dairy cow?
- UCT = 26°C
- LCT = -37°C to 16°C
What it absolute humidity?
This is a measure of the actual amount of water vapour present in a given quantity of air (g/m3)
What is relative humidity?
This is a measure of the amount of water vapour present in the air, expressed as a percentage of the maximum amount of water which the air is capable of holding when it is saturated at that particular air temperature
How does humidity affect thermal comfort?
A higher relative humidity makes it feel warmer, whereas a lower relative humidity makes it feel colder.
The absolute humidity ... with each 10°C rise in temperature?
Pathogens survive less well at high/low relative humidity?
List reasons why adequate ventilation is very important
- It removes moisture, decreasing relative humidity
- It removes noxious gases and replenishes oxygen
- It removes pathogens and particles
How many air changes per hour will a 'well ventilated' building have?
What are the different means of ventilation?
- Active - fans (with or without ducting)
- Passive - stack effect, cross wind, inlets
What drives the stack effect?
The stack effect is driven by heat generated within the building (by livestock)
We do we control humidity in livestock buildings?
- Prevent condensation on internal surfaces and consequent deterioration of materials
- Enable bedding and flooring to dry out
- Reduce pathogen load
- Prevent animals coat becoming wet which increases heat loss
- Provide a more pleasant environment for stock and workers
What are the 4 main moisture sources?
Urine, faeces, respiration and rain ingress
List some examples of noxious gases
CO2, NH3, H2S - slurry gas, CH4 - methane
How do we control temperature?
- Direct heating
- Control ventilation and drafts
- Stocking density/airspace allowance
- Evaporative cooling in hot climates
Describe the differences between climatic and controlled environment housing
Climatic housing has a lower stocking density than controlled environment housing. It also has a larger cubic air space per animal. Climatic housing is not well insulated whereas controlled environment housing is well insulated. Climatic housing is usually naturally ventilated whereas controlled environment housing has carefully controlled ventilation. Controlled environment housing is normally more expensive to construct and artificially lit. Climatic housing is more suited to ruminants, horses and adult pigs (with a low LCT), whereas controlled environment housing is more suited to piglets and chickens (with a higher LCT).