ANSC 433 Lecture Notes - Lecture 9: Atwater System, Good Energy, Adipose Tissue
23 May 2018
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9. ANSC 433: Animal Nutrition & Metabolism Chantal Coutu
1
Energy Metabolism
Energy
- Definition: the potential to perform
- Units:
o 1 cal = 4.184 joules (J)
o Kilocalorie (kcal) = 1 000 c alories (cal)
o Megacalorie (Mcal) = 1 000 Kcal
- Higher units for nutrient energy in large animals since calories would be in the thousands (if not more)
Energy Partitioning in Animals
- Energy in feed = GE
o Some lots, some absorbed = digestible energy
- Portion of that will be Metabolizable, some will be lost as heat (which is why
we measure heat production)
- End with net energy
o For maintenance of the animal
- Productive energy = retained energy
o Adipose tissue
o Meat is part of retained energy
o Milk, eggs, wool = products of animal production = retained energy
Gross Energy
Gross energy (GE) is the amount of heat resulting from complete oxidation of a unit
weight of food. The values are measured using bomb calorimetry. Some GE values for
nutrients:
o 4.10 Kcal/g carbohydrates
▪ contain a fixed ratio of C:O:H
o 5.65 Kcal/g proteins
▪ higher because also contains N and S which can also be
oxidized
o 945 Kcal/g fats
▪ more than twice the energy as carbohydrates since there are
more carbons and less oxygen therefore needing more
oxygen to oxidize all the carbons
o energy increases as the number of carbons increases
- GE values are of little use for animals eating high fiber diets
- Not really a good measure for animals
o Biggest loss of energy is in the feces
Digestible Energy
- Digestible energy (DE) represents energy absorbed by the animal
o Good energy unit measure for swine and horses
- Apparent DE is calculated as the GE in food minus the FE content in the
feces
- Fecal energy loss represents by far the most important and variable loss
of energy from animal foods.
Total Digestible Nutrients
- Total Digestible Nutrients (TDN) is the sum of all the nutrient fractions in a feed that are digestible
-
� = + + + . ∗
- Where D is digestible, CP is crude protein, CF is crude fiber, NFE is N-free extract (water, ____ and ____; measured by
difference: measure of digestible carbohydrates) and EE is ether extract (fat removed)
- Multiplied to account for the higher digestible energy in the fat
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9. ANSC 433: Animal Nutrition & Metabolism Chantal Coutu
2
- TDN tends to overvalue roughages as compared to ME and NE
- TDN has a similar, but DE and NE are values most often used in North America
Metabolizable Energy
- Metabolizable energy (ME) represents the energy that is available for use by the animal and is calculated as DE minus
energy lost in urine and combustible gases
o Energy available for metabolism
o Account for urine energy = count the urea, uric acid (in poultry) : are combustible energy sources that are
excreted
- ME is commonly used for poultry because urine and feces are excreted together
- If it aot e used for eergy the it should’t be in the metabolizable energy
- In ruminants, the combustible gases produced in the rumen and hind gut consist almost entirely of methane
o 8% of GE at maintenance;6-7% of GE at higher feeding levels
- In non-ruminants, losses of combustible gases are negligible and are normally ignored in computing ME
- Most ME values found in tabular data for feedstuffs evaluation are calculated values
- The ME value of a food will vary, depending on the species of animal to which it is given or on the type of digestion to
which it will be subjected
- Brewer’s grai ad silage are partially fereted efore eig fed to the aial = lesser losses of ethae fro the
animal since it was already lost in previous fermentation
- Energy loss in urine is higher in ruminants that non-ruminants
Factors Affecting ME Values of Food
Net Energy
- Net energy (NE) is the portion of energy available to the animal for maintenance or various productive purposes (i.e.
retained energy)
= −
- Heat increment of food (HIF) is heat production associated with nutrient digestion and metabolism over and above
that produce prior to food ingestion
- NE used for maintenance is mainly used to perform work within the body and will leave the animal as heat
o To measure net energy: net to measure heat production and amount of energy retained (NE = RE – HIF)
- Retained energy (RE) refers to energy used for growth, fattening and for milk, egg or wool production either is stored
in the body or leaves it (e.g. milk, eggs)
EXERCISE
Utilization of Metabolizable Energy
Efficiency of ME Utilization
Mem = metabolizable energy for maintenance is the point where the
energy is no longer consumed for maintenance of the animal
As you move forward, energy will be retained in the form of milk, wool,
eggs, etc. produced.
The K factor is the slope of the line. Km is used for the maintenance.
Efficiency Factors of ME Utilization
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Document Summary
Kilocalorie (kcal) = 1 000 c alories (cal: megacalorie (mcal) = 1 000 kcal. Higher units for nutrient energy in large animals since calories would be in the thousands (if not more) Portion of that will be metabolizable, some will be lost as heat (which is why we measure heat production) Productive energy = retained energy: adipose tissue, meat is part of retained energy, milk, eggs, wool = products of animal production = retained energy. Gross energy (ge) is the amount of heat resulting from complete oxidation of a unit weight of food. 4. 10 kcal/g carbohydrates contain a fixed ratio of c:o:h. 5. 65 kcal/g proteins higher because also contains n and s which can also be oxidized. 945 kcal/g fats: more than twice the energy as carbohydrates since there are more carbons and less oxygen therefore needing more oxygen to oxidize all the carbons energy increases as the number of carbons increases.
