Nutritive Value

Question 1

Feeds differ in….

Answer 1

nutrient composition
economics (cost to produce/cost per ingredient)

Question 2

Proximate analysis

Answer 2

lab testing of feeds to estimate nutrient composition

Question 3

What are the six types of proximate analysis?

Answer 3

1. Dry Matter (DM) - water content
2. Crude protein (CP) - crude protein/nitrogen content
3. Ether extract (EE) - lipid content
4. Ash - mineral content
5. Crude fiber (CF) - fiber content
6. Nitrogen Free extract (NFE) - carbs/starches/sugars

Question 4

What does dry matter (DM) tell us about a feed? How is dry matter found in the lab?

Answer 4

Dry matter tells us the water content of a feed as a percentage of how much is NOT water
ex) a feed with a dry matter of 70% is 30% water

Dry matter is found by weighing a feed, putting it in an oven (55-105 C) and weighing it after (the water all evaporates off)

Question 5

What does crude protein (CP) tell us about a feed? What is the method of determining crude protein called?

Answer 5

Crude protein tells us how much nitrogen is in a sample

CP determination is done via the Kjeldahl method

Question 6

How is CP calculated?

Answer 6

Crude protein (%) = % nitrogen * 6.25

Question 7

How many grams of nitrogen are there in 100 grams of protein?

Answer 7

16g

Question 8

What does ether extract (EE) measure? How is it found in the lab?

Answer 8

Ether extract measures lipid content

It is measured by weighing the sample, extracting all ether, and reweighing the sample (lipid is extracted)

Question 9

Fat has ____ times more energy than carbohydrates.

Answer 9

2.25

Question 10

What does ash measure? How is it found in the lab?

Answer 10

Ash measures mineral content of a sample

The sample is burned at a very high heat, such that all organic matter is burned away

Question 11

What is crude fiber (CF)? How is it found in the lab?

Answer 11

CF finds the indigestible carbohydrate content of a sample

It is found by simulating both acid and alkaline digestion

Question 12

Why is crude fiber not used for ruminants?

Answer 12

crude fiber does not account for fermentation that occurs in the rumen

Question 13

What does Nitrogen Free Extract (NFE) measure? How is it calculated?

Answer 13

NFE includes nutreints that slip through other methods of proximate analysis, mostly digestible carbohydrates, vitamins, etc

NFE = 100 - (%CP + %water + %EE + %CF + %ash)

Question 14

How are vitamins and minerals measured in feed

Answer 14

Vitamins and minerals are best calculated in bigger labs
Vitamin content is found via microbiological procedures and chemical procedures
Mineral content is found via chemical procedures

Question 15

What is the Van Soest Method?

Answer 15

Measures fibers in terms of how they are utilized by ruminants

Question 16

How does the Van Soest method work?

Answer 16

the sample is boiled in a neutral detergent, which separates neutral detergent solubles (soluble carbs, starch, CP, fat etc) from neutral detergent fibers (hemicellulose, cellulose, lignin). NDFs are then boiled in an acid detergent, which separates acid detergent solubles (hemicellulose) from acid detergent fibers (cellulose, lignin). The ADFs are boiled in 72% sulfuric acid, which leaves only indigestible lignin.

Question 17

What are the NDFs

Answer 17

hemicellulose, cellulose, lignin

Question 18

What are the ADFs

Answer 18

cellulose, lignin

Question 19

What does NDF predict? What does ADF predict?

Answer 19

NDF predicts intake
ADF predicts digestibility

Question 20

Is energy a nutrient?

Answer 20

NO

Question 21

Ice calorimetry

Answer 21

a mouse was kept in a chamber full of ice. the amount of ice that melted indicates how many calories the mouse burned

Question 22

Calorie

Answer 22

the amount of energy that it takes to raise the temperature of 1g of water by 1 degree C

Question 23

Kcal

Answer 23

1000 Calories

Question 24

Mcal (megacalorie)

Answer 24

1000 Kcal (or 10^6 calories)

Question 25

Where is energy derived from?

Answer 25

Simple carbs - starch/sugar
Carbs - Fiber
Fats
Proteins

Question 26

Atwater Physiological Fuel Values

Answer 26

The atwaters fuel values assigns an energy value to each nutrient
Carb - 4.20 Kcal/g
Fat - 9.45 KCal/g
Protein - 4.20 KCal/g

Question 27

Bomb calorimetry

Answer 27

combust a sample of feed and measure the amount of heat it gives off to find the caloric content

Question 28

What does bomb calorimetry tell you about a feed?

Answer 28

The gross energy (GE)

Question 29

What does Total Digestible Nutrient tell us about a feed? How is it calculated?

Answer 29

it predicts the energy content for ruminants
TDN = (%dCP + dNFE% + dCF% + (2.25*dEE%))

Question 30

In which situation would it be inappropriate to use TDN?

Answer 30

monogastric animals like swine and poultry

Question 31

What can TDN tell you about the intake of feed

Answer 31

animals will only eat feeds with a high TDN up to a certain point - there is an optimal TDN after which intake levels decrease

Question 32

How can gross energy be divided?

Answer 32

gross energy can be divided into digestible energy and fecal energy (energy lost in feces)
digestible energy can be divided into metabolizable energy, urinary energy, and gaseous energy (energy lost in fermentation)
metabolizable energy can be divided into net energy and heat production
net energy can be divided into net production energy (energy needed for eggs/meat/milk), and net maintenance energy (energy needed to live)

Question 33

What is the difference between the van-soest method and the total digestible nutrients (TDN)

Answer 33

van soest is a measure of how much FIBER is digestible in feed for ruminants
TDN is a measure of ENERGY content of a feed for ruminants