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

  1. What is the maximal energetic efficiency for production? When is it maximal. All feed is eaten

Feed is at 1 maintenance, work is at zero, at 32-40 *C --> no production, no work

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
  1. is 30*C end of thermoneutral, comfort or homeothermic zone?

It is the end of the comfort zone, probably
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Available feed: 2 MEm
  1. What is LCT for maintenance
  2. What is UCT for maintenance

LCT is 20 *C

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


  1. In the sun, only half ext. work can be performed at 38*C. Calculate heat production and extra heat load by solar radiation

Work = 4xM


Total heat production is now 1+3 = 4xMEm
Total EE = 1+4 = 5MEm

the extra heat load = 3xME (7-4=3)

  1. What can happen to the chemical (gross) energy of nutrients after ingestion?
  2. What can happen to the energy trapped in ATP?


  1. Loss in faeces; ME anabolic + catabolic processes --> ATP excretion of N via urea in urine
  2. ATP
    1. anabolic: storage, synthesis, heat
    2. exercise: external power and heat

Energy versus heat balance
  1. What does this mean in terms of metabolisable energy?
  2. What does this mean in terms of heat?

  1. Energy balance is not equal to heat balance
  2. 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

  1. Feed intake is too restricted to maintain a higher body temperature
  2. The heat loss is too high to maintain a higher body temperature
  3. Neither a nor b is correct

3. Neither a nor b is correct

Heat production
What is true
  1. The level of heat production is regulated to maintain the body temperature?
  2. The level of heat loss is regulated to maintain the body temperature?

  1. The level of heat production is regulated to maintain the body temperature?
    1. Yes, i.e. below LCT
  2. The level of heat loss is regulated to maintain the body temperature?
    1. Yes, i.e. above body temperature / UCT

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