Pet Food Energy Protocol
I. Animals
A minimum of six (6) fully grown animals at least one (1)
year of age complete the test. The animals shall be in good health and of known
we Animals shall be individually housed in metabolism cages. If urine is not
collected and metabolizable energy is calculated based on correction factors
urine energy loss as specified in the protocol, protected covered runs may used
in lieu of metabolism cages.
II. Feeding Procedures
Feeding procedures shall be standardized. The feeding
shall consist of two phases. The first phase shall be the pre-collection period
of at least five (5) days with the objective of acclimating the test
animals to the diet and adjusting food intake, as necessary, to maintain body
weight. The second phase shall be the total collection period of at least five (5)
days (120 hours). The amount of food offered during the second phase shall
remain constant. Food intake shall be recorded throughout both phases.
III. Food
Food type, flavor, and production codes representing the
composite feed shall be recorded. The food source shall remain constant
throughout the test period.
IV. Food Allowances
The amount of food presented to each animal may he based
upon existing data on the quantity of food required to maintain body weight, or
the estimated daily energy needs required for maintenance of various weights of
dogs (Table 5, 1985 Nutrient Requirements of Dogs, NRC, or 132 kcal ME
times body weight in kilograms to the 0.75 power) or cats (Table 4,
1986 Nutrient Requirements of Cats, NRC, or 70 kcal ME per kilogram body
weight). Ad libitum feeding also may be used.
V. Times of Feeding
Animals shall be fed at least once daily at the same time each day. Water shall be available at all times. Food shall be fed as is, or per normal feeding instructions for the product. The excess after the feeding shall be weighed back after the feeding.
VI. Pre-Trial Termination
If, during the pre-collection phase, the food is
continually rejected or results in minimal consumption by a majority of the
animals, the trial shall not proceed into the collection phase.
VII. Faeces Collection
It is imperative that all collection containers be clearly
marked using double labels. The labels shall include the animal number, diet
number, and dates of collection. Faeces shall be collected daily over 120 hours.
Every effort should be made to collect all of the faeces and avoid collecting
hair. The methodology is as follows:
1. Weigh collection container and record weight.
2. Place faeces in the respective animals container for that day of collection.
Collect faeces as quantitatively as possible.
3. Place collections in freezer for storage.
4. Faeces may be dried each day.
a. Weigh and record the weight of the faeces and container each day, and determine net weight of faeces. If the volume of faeces is large, an aliquot may be retained for drying.
b. Dry daily faeces collection (or aliquot). Faeces should be thin enough to dry quickly. Otherwise, nitrogen and carbon losses may occur due to fermentation products.
c. Composite the entire 120-hour collection or
proportional aliquots.
VII. Sample Preparation
A. Food
The food shall be blended to ensure a uniform consistency
and an adequate quantity used for appropriate assays. Ample quantities of the
remaining sample should be frozen and retained until assay results have been
reviewed and found acceptable.
B. Faeces
Faeces shall be analyzed using composite samples. The
samples shall be blended to ensure a uniform consistency and an adequate
quantity used for appropriate assays. Ample quantities of the remaining sample
should be frozen and retained until assay results have been reviewed and found
acceptable.
C. Urine
If urine collections are made, they shall be for the same
period as the feces collections. Urine shall be collected, with a minimum of
contamination, in a urine receptacle containing sulfuric acid to stabilize the
urine and prevent nitrogen loss. After the total urine volume is determined,
aliquot samples shall be freeze-dried in an appropriate container.
IX. Analytical Determinations
Prepared samples shall be used for analysis. A.O.A.C.
approved analytical methodology shall be used when available. Food, faeces, and
urine (if collected) shall be assayed for gross energy (bomb calorimetry). If
urine is not collected, food and feces also shall be assayed for crude protein.
X. Calculation of Metabolizable Enemy
The determination is based on assays of the gross energy
consumed, minus the energy in the feces and correction for energy lost in the
urine (or energy lost in urine as determined by calorimetry).
A. Without urine collection
ME = [gross energy of food consumed - gross energy of feces collected
- {(grams protein consumed - grams protein in feces} x
correction factor for energy lost in urine)]/amount of food consumed
Correction factor for energy lost in urine = 1.25 kcal/g
for dogs, 0.86 kcal/g for cats
Example:
a. gross energy of food = 4.35 kcal/g
b. amount of food consumed = 1250 g
c. gross energy of faeces = 1.65 kcal/g
d. amount of faeces collected = 600 g
e. protein in food = 24%
f protein in faeces = 9%
g. correction factor (dog) = 1.25 kcal/g
a X b = 4.35 X 1250 = 5437.5 kcal gross energy of food consumed
c X d = 1.65 X 600 = 990 kcal gross energy of feces collected
b X e/100 = 1250 X 24/100 = 300 g protein of food consumed
d X f/100 = 600 X 9/100 = 54 g protein in faeces
(300 - 54) X 1.25 = 307.5 kcal energy lost in urine
B. With urine collection
ME = (gross energy of food consumed - gross energy of feces collected
- gross energy of urine collected)/amount of food consumed
Example:
a. gross energy of food = 4.35 kcal/g
b. amount of food consumed = 1250 g
c. gross energy of faeces = 1.65 kcal/g
d. amount of faeces collected = 600 g
e. gross energy of urine = 0.25 kcal/ml
f. volume of urine = 1230 ml
a X b = 4.35 X 1250 = 5437.5 kcal gross energy of food consumed
c X d = 1.65 X 600 = 990 kcal gross energy of faeces collected
e X f 307.5 kcal gross energy of urine collected