QUESTIONS

1. How many Calories are there in a pound of fat (all us dieters know this one.)
    
2. The lateral hypothalamus, the ventromedial hypothalamus.  Which one contains the satiety center?
    
3. Physically speaking (as in Physics) what is the definition of a calorie?
    
4. Define & distinguish between:
   
   a) gross energy of a diet
   
   b) digestible energy of a diet
   
   c) metabolizable energy of a diet
   
   d) net energy of a diet
    
5. The most common form of malnutrition is _______________.
    
6. Basal metabolism is calculated by taking the weight in kilograms to the 3/4 power.  What is the name of this equation?
    
7. Go get a bag of pet food. Right now.  I'll wait.  Got one?  Good.  Look at the proximate analysis.  Why doesn't it add up to 100%?
    
8. What is "crude protein" a measure of (ie how is it measured)?
    
9. What is "crude fat" a measure of?
    
10. What is "ash"?
     
11. What is "Nitrogen Free Extract" supposed to represent?
     
12. Extra bonus question:  What's the difference between "biscuit"  & "Kibble?"
    
    
    
    
     

ANSWERS

1. There are 3500 Cal in a pound of fat according to the vet nutritionists at UCD (though I've also heard human diet people say 3600).
   
   
   
   
    
2. The ventromedial hypothalamus contains the satiety center.  Lesions here cause one to eat uncontrollably (could be my problem).  Lesions in the lateral hypothalamus cause aphagia.
   
   
   
   
    
3. A calorie is the amount of heat required to raise one gram of water one degree centigrade.  This unit is too small for nutritional study so we use kilocalories (Calories with a capital "C").
   
   
   
   
    
4. Okay, let's start with gross energy.  Take the food & put it in a bomb calorimeter & burn it.  The amount of calories you generate burning it is the gross energy.  But, of course, this is a far cry from the amount of calories a dog might actually get to use from the food.  To get the digestible energy, we take the gross energy of the food that we know & subtract from it the gross energy of the feces produced after the dog eats the food (that's pretty gross energy!  I wouldn't want to clean the bomb calorimeter after).  But we still don't have a measure of the energy the dog gets to use.  We'll get closer with metabolizeable energy.  Take the gross energy of the food, subtract the gross energy of the feces, of the urine, & of any relevant gases (such as methane gas burped out by a digesting cow) produced during digestion process. Now we have the metabolizeable energy but we still haven't taken into account the heat energy/calories burned by the act of digestion.  Subtracting this (which is called the "heat increment") from the metabolizeable energy yields the net energy which is as close as we get to the keepable/useable calories from the food.
   
   
   
   
    
5. The most common form of malnutrition is obesity.
   
   
   
   
    
6. This popular equation is used to calculate caloric demands in different metabolic states and is called the "Kleiber equation."  Okay, so what if a guy named Hausner found it to be inaccurate recently.  The Kleiber equation is still what's in most text books.  Technically speaking it is more correct to use the 2/3 power instead of the 3/4 power.)
   
   
   
   
    
7. Those tricksters always leave something out. Usually it's "nitrogen free extract" (see later) which is left out.  You're supposed to know what has been left out so that when you add the other guys up & subtract from 100, you get the nitrogen free extract.
   
   
   
   
    
8. Crude protein is measured by what's called the Kjeldahl method.  (I'm sure this is all coming back to you).  Food is digested w/sufuric acid thereby converting nitrogenous components into NH4+ salts.  The digest is then alkalinized to free NH3 which is then distilled off &measured.  This means in English that "crude protein" is a measure of nitrogenous food constituents.  (Of course, this includes nucleic acids, & urea (both of no value to non-ruminants), not just amino acids.)  "Crude protein" also does not yield any info on the quality of protein in a food.
   
   
   
   
    
9. "Crude fat" is also called "ether extract" which kind of gives away what it is a measure of.  Lipid solvent is used to remove lipid components of food which are mostly triglyerides but are also phospholipids & cholesterol.
   
   
   
   
    
10. To be honest, I don't believe a food is allowed to put an "ash" content on a label anymore.  Does any one know for sure?  Ash is the mineral content of a food.  (the food is incinerated & ash is the leftovers.)  "Ash" is such a mixed bag that it says absolutely nothing about which minerals it might include (salt? dirt? etc.).
    
    
    
     
11. "Nitrogen-free extract" is supposed to represent the digestible carbohydrates.  It is usually left off the lable & calculated by subtracting ash, protein, and fat content from 100.
    
    
    
    
     
12. Food is so defined!  Biscuit is shaped, baked dough.  Kibble is cracked or crushed baked dough.  Yum, Yum