Chemical compounds of feed

Question 1

Feeds

Answer 1

Spp dependent, not all feeds useable for all animals
- are edible materials,
- contain nutrients,
- are capable of being digested
Chemical compounds of feeds <=> nutrient requirements of animals.

Question 2

Proximate Analysis.

Answer 2

analyse the main nutrients of feeds: 150yo primary analysis of feeds

1) dry matter -water
2) ash-organic matter
3) CP-EE-CF-NFE

Question 3

Dry Matter (DM) 1. Voluminous feeds

Answer 3

Low DM content related to the volume
green forages and preserved forages (hay, silage).
large amounts needed to provide adequate nutrition

Question 4

Dry Matter (DM) 2. Concentrated feeds

Answer 4

High level of energy within the DM E.g. cereal grains

full of starch and energy so low volumes are needed

Question 5

Dry Matter (DM) 3. DM intake capacity of animals

Answer 5

how much feed can be fed-> determined by BW (Eq approx. 2% BW)

Question 6

Ash

Answer 6

− 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).
determined by burning the feed

Question 7

Crude Protein (CP)

Answer 7

Nitrogenous compounds, Determination with – Kjeldahl Method according to proximate analysis

1. Degradation N containing substances + H2SO4 => (NH4)2SO4
2. Liberation of ammonia (NH4)2SO4 + NaOH =>2 NH3 (capture of NH3 with boric acid)
3. Back-titration ammonia-N + HCl =>N

CP= N*6.25 (100:16=6.25)

separated into true protein and non-protein-nitrogen (nitrates, free amino acids, amides, nucleic acids, etc.)
− Monogastric animals need true protein (amino acids); − Ruminants can partly utilize the nitrogen as a protein source.

Question 8

True Protein

Answer 8

− True protein: built up from amino acids;
− True protein can be produced from protein only;
− all of the animal cells contain proteins (and enzymes, hormones as well);

Question 9

Ether Extract (EE)

Answer 9

fats and oils, (everything soluble in ether)
− energy sources,
− oils: essential fatty acids (omega 6, omega 3).
Determination with Soxhlet method according to proximate analysis

Question 10

Crude Fibre (CF)

Answer 10

plant cell wall compounds (hemicellulose, cellulose, lignin, pectin)
-in rumen: volatile fatty acids will be built (e.g. acetic acid  milk fat),
− stimulates the chewing  saliva production  NaHCO3  buffers the rumen content (pH)
− influences the nutrients’ digestibility (fibre optimum of different species),
− dietetic effect: passage of digesta.

most criticized method in prox analysis

1. Boiling of a ground feed sample in a weak acid solution (1.25% H2SO4, 30 minutes)
2. Filtering
3. Boiling in a weak solution of alkali (1.25% KOH, 30 minutes)
4. Filtering and drying.=> only substances that can survive acid and alkali are cellulose, hemicellulose and lignin

Question 11

Nitrogen-free Extract (NFE)

Answer 11

mainly (but not exclusively) starch, - energy source.
calculated, not chemically estimated
1) DM-(Ash+CP+CF+EE)
2)NFE(%)=100-(CP%+CF%+EE%+Total Ash%)