Feed analyses 1

Question 1

Dry matter properties…?

Answer 1

Main feed parameter
Proportions vary (20% silages, 90% grains)
Determined by drying a known amount for 16 hours, then reweighing

Question 2

Organic matter properties…?

Answer 2

Determines ash/mineral content of feed
High values may indicate contamination
Determined by burning combustible material

Question 3

Describe proximate (Weende) analysis

Answer 3

Combo of analytical procedures from Germany
Still widely used
Many faults - crude fibre
Attempts to isolate water, ash, crude protein/fibre, ether extract…

Question 4

Crude protein properties…?

Answer 4

Nitrogen x 6.25 = CP value
NaOH added once cool
Contains: true protein AAs, & non-protein nitrogen (urea)

Question 5

Ether extract (fat extract) properties…?

Answer 5

Fat content of feed
Components extracted: true fats, waxes, alcohols…
Proportion of feed with high energy values

Question 6

T or F - If ether extract contains a high proportion of fats, method is not valid for estimating energy content

Answer 6

False

Question 7

Crude fibre properties…?

Answer 7

mainly structural carbs
widely used
not repeatable
Attempts to simulate stomach digestion SI

Question 8

How is crude fibre determined?

Answer 8

Boil ether extract in acid & base -> filter residue off -> dried & weighed -> difference between dried & ashed = CF

Question 9

Nitrogen-free extracted properties…?

Answer 9

Useful for est. soluble carb fraction of grains
Measures difference original sample weight & (sum of water, ash ether, crude fibre & protein)
Primarily soluble carbs (sugars & starch)

Question 10

What is nitrogen-free extract useful for?

Answer 10

Estimating soluble carb fraction of grain (variable for roughages)

Question 11

Neutral detergent fibre (NDF) process…

Answer 11

Most common measure of fibre
Measures structural components (cellulose, hemicellulose, lignin) by boiling sample in ND solution (remove cell wall contents) -> residue

Question 12

Acid detergent fibre properties…?

Answer 12

Removes/isolates hemicellulose & cell wall contents

Residue contains cellulose & lignin

Question 13

NDF - ADF = ?

Answer 13

hemicellulose

Question 14

Describe in vivo digestibility

Answer 14

Difference between dry feed offered & faeces excreted as %
Animals confined or fitted with faecal collection bags
Feed in & poo out recorded over several days
Benchmark!!!
Time consuming & expensive

Question 15

Estimating digestibility?

Answer 15

Indigestible marker (lignin/waxes)

Question 16

In vitro digestibility

Answer 16

More feasible & time-efficient
Ruminants - Incubate sample in rumen for 2 days -> pepsin 2 days - residue left = indigestible
Horses - strained faecal fluid
Pepsin/cellulase technique

Question 17

In Sacco digestibility?

Answer 17

‘Nylon bag’ technique -> contains feed incubated in rumen of fistulated animals - good for time studies

Question 18

Factors affecting digestibility (feed factors)?

Answer 18

Food composition (fibre)
Ration composition
prep - chaffing, crushing, grinding; cooking…

Question 19

Factors affecting digestibility (animal factors)?

Answer 19

Kind of animal - ruminant vs monogastric
Feeding level - more food -> faster passage -> lower digestibility
Previous feeding - microbial pop. Takes time to adjust to new feed