The animal and its food
• Food: materials that covers the requirements
of animals
–
–
–
–
maintenance
growth
physical activity
production
• Nutrients: Components of foods and
animals
– protein, fat, carbohydrates, vitamins, minerals
etc.
– the nutrients of foods are only partly absorbed
and utilised
Some differences between the composition of
animals and plants
• Carbohydrate content: plant > animal
– Plant cell wall: cellulose, hemicellulose, etc.
– Animal cell wall: protein, lipids
• Fat content: animal >=< plant
– plants: stored nutrient is mostly starch
– But there are oil seeds too
– animals: the main energy store is fat
• Protein content: animal >=< plant
– Changing with the age
• Fibre content: only plants
• Vitamins: plants are self-sufficient, animals not
• Minerals: plants (N, P, K); animals (Ca, P)
Nutrient content of some foods (g/kg)
water dry
matter
fat
protein
fibre
digestible
carbohydrate
ash
leafy grass
780
220
11
44
45
98
22
wheat grain
130
870
19
122
23
689
17
milk
876
124
36
33
-
47
8
potato
760
240
1
22
7
197
13
soybean
seed
110
890
190
340
70
250
34
extracted
soybean
100
900
14
493
33
294
66
sunflower
seed
84
916
460
180
155
90
34
meat
720
280
42
214
-
6
15
Components of different fractions in the proximate analysis
of foods
food sample
dry matter
water
ash
organic materials
contamination (soil,
sand etc.)
true ash
crude protein
crude fat
real protein
amid materials
crude fibre
Nitrogen-free extracts
The Van Soest cell wall analysis
• Neutral detergent fibre (NDF)
– boiling the food sample in a neutral detergent
– containing cellulose, hemicellulose and lignin
• Acid detergent fibre (ADF)
– boiling in acidic solution
– containing cellulose and lignin
• Acid detergent lignin:
– undiluted acidic treatment
– containing only lignin
Other analytical procedures
•
•
•
•
•
amino acids: ion exchange liquid chromatography
fatty acids: gas chromatography
sugars, starch: photometer
minerals: atomic absorption
gross energy: bomb calorimeter
The water content of foods
• Animals 50 - 80%
• The animals can not tolerate water
deprivation for a long time
• Main roles:
–
–
–
–
transport of nutrients
excretion of waste products
enzyme functions (hydrolysis)
regulation of body temperature
Water sources:
drinking water
water content of the food
metabolic water (oxidation of fats and
carbohydrates)
According to their water content foods can be:
liquid – juicy –
dry
milk
pumpkin
cereal seeds
whey roots
extracted meals
green-leafy foods
wheat bran
The water content of foods has an impact on the
• nutritive value (concentrated; mass foods)
– concentrated: containing high amounts of energy and
protein, less fibre and water
– mass foods: containing high amounts of water, fibre,
less other organic nutrients
• transportation of foods
– transportation of water is not worth
• keeping time (grains 14%; mixed feeds, meals
12%; hay 16-18%)
• production of milking animals
– a foods with high water content improve the milk
production
Dry matter content of foods
• original DM - 100% DM – air-dried DM
• original: the DM which is true at the time of harvest or if the food is
used for nutrition
• 100% DM is an analytical category, when the total water
content is evaporated
• air-dried DM: the totally dried sample takes the water
content of the air, and its weight will be stable (84-86%)
• DM will determine the feed intake of animals (physical
capacity)
• It has an impact on the satiety
• Higher DM means mostly more nutrients