Yeah

Question 1

What are the assumptions of DLW?

Answer 1

. Body water remains constant
. Can’t use this on young animals as some of the labels will be incorporated into the tissues as the animal is still growing/ tissues are being laid down
. Rates of water and CO2 flux remain constant
. Isotope label only the body water (not incorporated into tissues)
. Isotopes only lost as CO2 and/ or H2O
. Specific activity of isotopes in water lost from the animal is the same as in the body water (H2^18O is heavier than H2O)
. Labelled or unlabelled CO2 and: or water does not enter the animal bibs respiratory or skin surfaces

Question 2

What are potential drawbacks of DLW?

Answer 2

. Only estimates the mean energy expenditure over the measuring period (the time you inject the animal to the time you take the final blood/ water sample, you will only get an estimate of the metabolic rate over that time period))- we are only estimating CO2 production and we need to convert that
. Not feasible to measure over short time resolution (talking about days as opposed to hours or minutes)- would entail a lot of disruption to the animal and you probably wouldn’t get a reasonable behaviour from the animal, so wouldn’t be a reasonable energy expenditure
. May have reduced precision in very active animals- v. High metabolic rates there may be a problem with the technique and the accuracy begins to trail away but very little that has looked at that most findings have shown a reduction in accuracy
. Can be problems trying to convert CO2 production to estimates of energy expenditure will all depend on the fuel that the animal is using at the time. If they are using carbohydrates and you think that they are utilising fat then your estimate can be at 54% out so have to know what they are metabolising, can try and reduce errors by just assuming that most animals are using a mixed fuel source

Question 3

How do you reduce errors in DLW?

Answer 3

Assume that most animals are using a mixed fuel source

Question 4

When using DLW and you think the animal in question is using carbohydrates and you think they are utilising fat then how out can your estimate be?

Answer 4

54%

Question 5

What is the only quantitative method for measurement energy expenditure in small animals?

Answer 5

DLW

Question 6

What are the things to consider when deciding which energy expenditure test to use?

Answer 6

. DLW is expensive and difficult to get hold of large quantities
. There is a limit of 5% of body weight for any external attachments
HR loggers 25g
HR transmitters 3G
. HR loggers are expensive
. Labour is expensive
. Accelerometry produces huge quantities of data
. Accelerometers do not work on sedentary animals