Chemical compounds of feeds

Question 1

What are feeds?

Answer 1

Feeds — edible materials, contain nutrients, are capable of being digested

Question 2

What is the first step of proximate analysis of feeds?

Answer 2

Determination of dry matter

Question 3

What are 5 reasons to determine dry matter?

Answer 3

1. Comparison of feeds based on their nutrient content
2. Identification of voluminous feeds (relationship between volume and DM)
3. Identification of concentrated feeds (relationship between DM and energy content)
4. DM intake capacity of animals
5. Storage quality and transportability of feeds

Question 4

Voluminous feeds — ?

Answer 4

Low DM content related to the volume of feed
.
Examples: green forages, preserved forages

Question 5

Concentrated feeds — ?

Answer 5

Lot of energy in the DM
.
Examples: cereal grains

Question 6

How do we determine DM?

Answer 6

By using drying oven

Question 7

What is the next step of proximate analysis after determination of DM? How?

Answer 7

• Separation of inorganic and organic compounds
• by determining the ash content of the feed which involves the inorganic compounds
• method: muffle furnace (500-600 Celsius)
• organic matter - calculated value

Question 8

What does ash consist of?

Answer 8

• inorganic compounds of feed
• mainly minerals + some inorganic contaminations (e.g. sand, soil)
• animals do not have a requirement for ash (they need individual mineral elements)

Question 9

What is the next step after determination organic and inorganic?

Answer 9

Separate the compounds of the organic matter
—
1. crude protein
2. ether extract
3. crude fibre
4. nitrogen-free extract (NfE) (is done by calculating)

Question 10

How to determine the CP content of a feed?

Answer 10

• more logically would be to measure amino acid a=content of feeds but analysis is old and back then they could nit measure amino acids
• element that is present in protein but missing from the carbohydrates and fats -> nitrogen -> determination of CP = determination of N content of the feed
• crude protein = N x 6,25 (but it’s not protein because not only proteins contain N

Question 11

What groups crude protein include?

Answer 11

True protein and non-protein-nitrogen compounds
—
- true protein: built up from amino acids and can be synthesised from protein only
- animal cells contain true protein
- monogastric animals need true protein (amino acids)
- ruminants can party utilise the nitrogen as a protein source via rumen microbes

Question 12

What belongs to NPN (non protein nitrogen)?

Answer 12

• nitrates
• free amino acids
• amides
• nuclei acids, etc
  —
  CONTAIN N BUT THEY ARE NOT PROTEINS

Question 13

What is ether extract (EE)?

Answer 13

All substances soluble in petroleum ether
1. true fats and oils: energy sources, essential fatty acids
2. other substances: glucolipids, phosphatides, waxes, steroids, terpenes, etc)

Question 14

How to determine EE?

Answer 14

Soxhlet method

Question 15

What is crude fibre?

Answer 15

Plant cell wall compounds (pectin, hemicellulose, cellulose, lignin)

Question 16

Why to determine CF?

Answer 16

• in rumen: volatile fatty acids will be built (e.g. cellulose -> acetic acid -> milk fat)
• stimulates the chewing -> saliva production -> NaHCO3 -> buffers the acids in the rumen
• influences the nutrients’ digestibility (fibre optimum in different species)
• dietetic effect: maintenance of peristalsis, passage of digesta

Question 17

How to determine CF?

Answer 17

Kinda imitating digesting: treatment with acids and alkali

Question 18

What is the nitrogen-free-extract?

Answer 18

Mainly (but not exclusively) starch. Energy sources.
Starch, sugar, organic acids, soluble pectins, hemicelluloses, cellulose, lignin