Nutritive Value Flashcards
Feeds differ in….
nutrient composition
economics (cost to produce/cost per ingredient)
Proximate analysis
lab testing of feeds to estimate nutrient composition
What are the six types of proximate analysis?
- Dry Matter (DM) - water content
- Crude protein (CP) - crude protein/nitrogen content
- Ether extract (EE) - lipid content
- Ash - mineral content
- Crude fiber (CF) - fiber content
- Nitrogen Free extract (NFE) - carbs/starches/sugars
What does dry matter (DM) tell us about a feed? How is dry matter found in the lab?
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)
What does crude protein (CP) tell us about a feed? What is the method of determining crude protein called?
Crude protein tells us how much nitrogen is in a sample
CP determination is done via the Kjeldahl method
How is CP calculated?
Crude protein (%) = % nitrogen * 6.25
How many grams of nitrogen are there in 100 grams of protein?
16g
What does ether extract (EE) measure? How is it found in the lab?
Ether extract measures lipid content
It is measured by weighing the sample, extracting all ether, and reweighing the sample (lipid is extracted)
Fat has ____ times more energy than carbohydrates.
2.25
What does ash measure? How is it found in the lab?
Ash measures mineral content of a sample
The sample is burned at a very high heat, such that all organic matter is burned away
What is crude fiber (CF)? How is it found in the lab?
CF finds the indigestible carbohydrate content of a sample
It is found by simulating both acid and alkaline digestion
Why is crude fiber not used for ruminants?
crude fiber does not account for fermentation that occurs in the rumen
What does Nitrogen Free Extract (NFE) measure? How is it calculated?
NFE includes nutreints that slip through other methods of proximate analysis, mostly digestible carbohydrates, vitamins, etc
NFE = 100 - (%CP + %water + %EE + %CF + %ash)
How are vitamins and minerals measured in feed
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
What is the Van Soest Method?
Measures fibers in terms of how they are utilized by ruminants
How does the Van Soest method work?
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.
What are the NDFs
hemicellulose, cellulose, lignin
What are the ADFs
cellulose, lignin
What does NDF predict? What does ADF predict?
NDF predicts intake
ADF predicts digestibility
Is energy a nutrient?
NO
Ice calorimetry
a mouse was kept in a chamber full of ice. the amount of ice that melted indicates how many calories the mouse burned
Calorie
the amount of energy that it takes to raise the temperature of 1g of water by 1 degree C
Kcal
1000 Calories
Mcal (megacalorie)
1000 Kcal (or 10^6 calories)
Where is energy derived from?
Simple carbs - starch/sugar
Carbs - Fiber
Fats
Proteins
Atwater Physiological Fuel Values
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
Bomb calorimetry
combust a sample of feed and measure the amount of heat it gives off to find the caloric content
What does bomb calorimetry tell you about a feed?
The gross energy (GE)
What does Total Digestible Nutrient tell us about a feed? How is it calculated?
it predicts the energy content for ruminants
TDN = (%dCP + dNFE% + dCF% + (2.25*dEE%))
In which situation would it be inappropriate to use TDN?
monogastric animals like swine and poultry
What can TDN tell you about the intake of feed
animals will only eat feeds with a high TDN up to a certain point - there is an optimal TDN after which intake levels decrease
How can gross energy be divided?
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)
What is the difference between the van-soest method and the total digestible nutrients (TDN)
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
