NP15 (assignments) thermoregulation
9 important questions on NP15 (assignments) thermoregulation
Calculate total heat load of this pig, given
- Metabolic weight = 80^0.75 = 26.7
- Feed intake 2.5 MEm
- Production efficiency = 70%
What is the composition of the heat load?
How much O2 is consumed by the pig?
- BMR = 400 x26.7 = 10680 kJ / day = MEm
- 2.5 MEm = 2.5 x 10680 = 26700 kJ/day
- 1.5 MEm for production:
- 0.7 x 1.5 MEm = 1.05 MEm product
- 0.3 x 1.5 MEm = 0.45 MEm production heat
- total heat: 1 MEm + 0.45 MEm = 1.45 MEm = 1.45 x 10680 = 15486 kJ/day
- feed = 2.50 x MEm
- heat = 1.45 x MEm --> 1 is for maintenance
- product = 1.05 x MEm
- Heat is needed to calculate O2
- 1 L O2 ± 20 kJ
- 15486 (kJ/day) / 20 (kJ/L) = 774 liter O2/day
Available feed: 2 MEm
- What is the maximal energetic efficiency for production? When is it maximal. All feed is eaten
At 10 *C feed is at 2 maintenance, work is at zero --> no production, no work
from 16-30 *C the production is at 0.6 maintenance and food intake is 2 maintenance. So, 1ME for production --> 60 % in product and 40% in heat
Available feed: 2 MEm
- is 30*C end of thermoneutral, comfort or homeothermic zone?
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Available feed: 2 MEm
- What is LCT for maintenance
- What is UCT for maintenance
UCT is unknown... But it is higher than 40*C
Physical activity test
- Cyclist; maintenance 7 kJ/min
- Upper critical temperature: 44 *C
- Max. evaporation: 22.4 ml/min
- External work (power): 14 kJ/min
- Max skin temperature: 37 *C
- Heat of evaporation: 2.5 kJ/gram water
- In the sun, only half ext. work can be performed at 38*C. Calculate heat production and extra heat load by solar radiation
Total heat production is now 1+3 = 4xMEm
Total EE = 1+4 = 5MEm
the extra heat load = 3xME (7-4=3)
- What can happen to the chemical (gross) energy of nutrients after ingestion?
- What can happen to the energy trapped in ATP?
- Loss in faeces; ME anabolic + catabolic processes --> ATP excretion of N via urea in urine
- ATP
- anabolic: storage, synthesis, heat
- exercise: external power and heat
Energy versus heat balance
- What does this mean in terms of metabolisable energy?
- What does this mean in terms of heat?
- Energy balance is not equal to heat balance
- Release of heat is limited under higher temps --> ME is used in another way. Heat load can not be halted/stopped; is just as heat present
Why is our body temperature 37*C
- Feed intake is too restricted to maintain a higher body temperature
- The heat loss is too high to maintain a higher body temperature
- Neither a nor b is correct
Heat production
What is true
- The level of heat production is regulated to maintain the body temperature?
- The level of heat loss is regulated to maintain the body temperature?
- The level of heat production is regulated to maintain the body temperature?
- Yes, i.e. below LCT
- The level of heat loss is regulated to maintain the body temperature?
- Yes, i.e. above body temperature / UCT
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