Chapter 9- Energetics (Nov 19)

Question 1

digestible energy=

Answer 1

amount of dietary gross energy not recovered from the feces and assumed to be digested and absorbed by the animal

Question 2

why does apparent digestible energy (aDE) not equal true digestibility?

Answer 2

endogenous losses

• cell sloughing (affected by diet)
• enzyme secretion

Question 3

what does true digestible energy compare?

Answer 3

• energy of fecal excretion of animal fed a test diet
  WITH
• energy of fecal excretion of an animal fed:
  
  • nothing
  • presumably entirely
    absorbed diet
  • intravenously

Question 4

is true digestible energy feasible for both monogastrics and ruminants?

Answer 4

no, not ruminants- only monogastrics

Question 5

when calculating true digestible energy, you subtract ___ from ____

Answer 5

extractions of second animal
minus
excretions of 1st animal (test diet)

Question 6

T/F

total digestible nutrients (TDN) is roughly comparable to DE

Answer 6

true

Question 7

what are 3 problems with the TDN data we have?

Answer 7

• based on old experiments
• only sheep have been used in experiments
• lower feed intake than modern production animals

Question 8

metabolizable energy (ME) accounts for:

Answer 8

• fecal energy
• urine energy
• combustible gas energy

Question 9

urinary energy losses come from:

Answer 9

absorbed/ metabolized nutrients and endogenous products

Question 10

gaseous energy losses come mainly from:

Answer 10

microbial fermentation

gaseous losses minor but variable in monogastrics

Question 11

gaseous products of digestion: (3)

• important for?
• increases with?

Answer 11

methane, hydrogen, CO2

• important for ruminants (~8% of total energy intake) and some hindgut fermenters
• inc with poor quality forage

Question 12

What is an issue with using ME in poultry?

- solution?

Answer 12

• cannot easily separate urinary and fecal losses

- solution= use nitrogen corrected ME (MEn)

Question 13

explain nitrogen corrected ME

Answer 13

it accounts for energy content of nitrogenous waste products

- used to calculate energy cost of synthesizing uric acid in poultry

Question 14

net energy =

Answer 14

• energy lost through production of heat

the portion of feed actually available to the animal for

1. maintenance
2. production

Question 15

T/F

ME is commonly used in ruminants

Answer 15

false

- b/c methane is difficult to measure

Question 16

heat increment =

Answer 16

difference between heat produced by a fasted animal minus heat produced in a fed animal

Question 17

heat of fermentation is poorly ___ but may be useful in ___ environments

Answer 17

quantified

cold

Question 18

___ energy loss is the largest loss of energy

Answer 18

fecal