Analysis in Nutrition Flashcards
What two main approaches are used to assess nutritive value of feeds?
- Laboratory assessment
- chemical analysis
- NIR
- in vitro digestion
2.animal assessment
- in vivo
What are the six classes of nutrients?
- water
- carbs
- proteins
- fats and fatty acids
- minerals
- vitamins
Describe proximate analysis.
Proximate analysis is always on a dry matter (DM) basis. (meaning it’s water free)
It determines protein, fat, fiber, organic matter (used to find ash), and nitrogen free extract.
How can dry matter and moisture be measured?
The ground sample is weighed, and dried until stable, then weighed again. (ex. oven, microwave, etc.)
This process is repeated until no weight change occurs.
What is the difference between dry matter and as fed basis?
As fed basis includes moisture while dry matter does not.
Feed is bought, sold, and fed on an as fed basis.
Nutrients are contained in the dry portion of the feed, and moisture content is variable.
Nutritionists normally balance diets based on DM and use it for feeding conversions. Water left behind can hinder other analyses.
How is DM calculated?
% DM = weight of feed after drying/weight of feed prior to drying x 100
What is crude protein?
The nitrogen content of the feed x 6.25.
Proteins are 16% N by weight, so 100/16 = 6.25
What animals need higher protein requirements?
Younger animals need a higher percent protein in their diet because of their rapid tissue growth and low feed intake.
What do protein requirements change with?
Age
Body Size
Level/Stage of production
Growth
Intake
Why does protein requirement change with body size?
The actual amount of protein intake in grams increases as body size increases, so the gram requirement increases.
How does level of production affect protein requirement?
Animals growing faster or milking more than their counterparts have a higher gram protein requirement.
What is included in crude fat?
Crude fat, aka ether extract, includes waxes, pigments, ether, etc.
What does crude fiber include?
Components of the cell wall, mostly cellulose.
What is crude ash?
The mineral content of the feed.
It is found by weighing a sample, incinerating it, and weighing the remaining inorganic material.
What is NFE?
Nitrogen free extract
It includes starch, soluble fibers, and sugars
How is NFE determined?
NFE = DM - CP - CF - EE - Ash
List all the categories of proximate analysis.
- Water
- Ether extract (crude fat)
- Crude fiber
- Crude protein
- Ash
- NFE
What is the Van Soest System?
This is a system developed by Peter Van Soest to better account for the fiber content. He did not agree with how Proximate Analysis divided carbs into crude fiber and NFE.
Is is also known as the detergent system.
The two types are Neutral Detergent Fiber (NDF) and Acid Detergent Fiber (ADF)
What does NDF include?
cellulose, hemicellulose, pectin, and lignin
What does ADF include?
cellulose, pectin, and lignin
How are proximate analysis and Van Soest integrated?
Proximate analysis is used to find DM, ash, EE, and CP.
Van Soest is used to find NDF in ADF as opposed to crude fiber and NFE.
What is NFC?
Non-fiber carbohydrates, the method used in the Van Soest system. It is not NFE.
Calculated as follows:
NFC% = 100 - (CP + NDF + EE + Ash)
It relies on NDF
Summarize the differences between NFC, NFE, and NSC.
NFC = non fiber carbohydrates, it relies on NDF
NFE = nitrogen free extract, uses CF, not NDF
NSC = non-structural carbohydrates, analyzed components (sugars, starches)
What is the most digestible fraction of the cell wall?
hemicellulose
feeds with higher hemicellulose are more digestible
How can Van Soest be used to determine hemicellulose?
NDF includes hemicellulose, ADF does not
Therefore, it can be found by NDF - ADF = hemicellulose
What other ways are minerals accounted for?
ICP = inductively coupled plasma
- can analyze all minerals at once
AA = atomic absorption spectroscopy
- runs samples individually
Discuss vitamins
Vitamins are part of the organic matter of a sample
How are vitamins accounted for?
HPLC = high-performance liquid chromatography
- used to quantify individual vitamin ammounts
What is NIR?
Near Infrared Reflectance
It shines infrared light on the sample and measures wavelengths of reflected light.
It’s based on a calibration set of previous wet chemistry (proximate analysis and Van Soest) analysis a computer program estimates.
Okay for analysis of NDF, ADF, and CP.
NIR is very poor for minerals and vitamins.
What are some other estimates of nutritional value of feed by chemical analysis?
- Starch and sugar better than NFC
- Amino acids and fatty acid profile (expensive and normally predictable)
- anti-nutritive factors (ex. molds and mycotoxins; expensive and many to test for)
- estimate physically effective fiber
- digestibility (predicted)
How can digestibility be estimated?
It can be estimated from ADF or lignin concentration.
As ADF increases, apparent digestibility decreases
How is apparent digestibility calculated?
(intake - amount excreted)/intake
What is in vitro analysis?
This is analysis “within glass” or in a test tube. It can be used to estimate feed digestibility.
ex.
Simulate rumen digestion by incubating feed in rumen fluid for 48 hours at body temp.
Incubating feed in pepsin at pH 2 for 48 hours to simulate gastric digestion
What is in vivo lab analysis?
In vivo means “in life.” This means the procedure is run using the animal.
What are the four major approaches of animal assessment for nutritional value?
- Digestion trial
- Balance trial
- Metabolism trial
- Production trial
What percent of their body weight do adult animals eat per day?
2-3%
What method of assessment is the gold standard of nutritional value?
Animal assessment aka in vivo
