ANN 111: Principles of Animal Nutrition and Feed Technology (2+1)

COMPOSITION OF PLANTS 

• The composition of plants shows wide variations. The principal constituent of living plants is moisture. The moisture content of plants is highly variable. Young plants have more moisture content. As the plant mature, the moisture content decreases.
• The dry matter of plant contains mainly carbohydrates. Carbohydrate serves as a structural and reserve material in plants. In seeds carbohydrates occur principally as starch while in stems and to a certain extent in leaves a considerable proportion of carbohydrate is present in the form of structural carbohydrates (cellulose, hemicellulose and lignin). The lignin content of plant tissues increases with maturity of the plant.
• Protein is primarily present in active tissue such as the leaf. As the plant mature there is migration of the protein from the leaves to the seeds to serve as a reserve material for germination. Young tissues of plant, fruits, and seeds, especially leguminous, are rich in protein.
• Fat is present at highest level in the seeds followed by leaves and stem. Oil-bearing seeds have higher percentage of protein and fat compared to cereals.
• The mineral content of plants is highly variable. It differs with species and plant parts and is also influenced by soil and other environmental factors.
• In plants there are various organic acids (citric, malic and fumaric), which are important for metabolism in the cells of plant.
• Vitamins both fat-soluble and water-soluble are also present in plants.

The percentage chemical composition of some plants and their byproducts

	Water	Protein	Fat	Carbohydrate	Ash
Green plants
Berseem	90.0	2.0	0.3	6.3	1.4
Cow pea	80.0	2.5	0.5	15.0	2.0
Maize	75.0	2.0	0.6	21.0	1.4
Pasture grass	84.0	3.6	1.0	10.0	2.4
Cereal grains
Wheat	13.0	12.0	2.0	71.2	1.8
Seeds
Groundnut	6.0	27.0	45.0	20.0	2.0
Plant byproducts
Paddy straw	10.0	3.5	1.5	70.5	14.5
Wheat straw	10.0	3.5	1.5	76.5	8.5
Rice bran	10.0	10.0	15.0	55.0	10.0
Wheat bran	10.0	10.0	3.0	70.0	7.0

Difference between plants and animals in their composition

S.No.	Parameters	Animal	Plant
1.	Major constituent	Water	Water
2.	% dry carbohydrate	1	75
3.	Reserve energy as	Fat	Carbohydrate (Starch)
4.	Structural component	Protein and mineral	Carbohydrate (Cellulose, hemicelluose)
5.	As source of protein	Good	Poor (except oil seeds)
6.	Mineral content	Constant to species	Variable
7.	Variation in composition	Less	Wide

Factors affecting chemical composition of plants

• Plant factor - Chemical composition of different varieties of same species of forage vary because of different genetic material.
• Agro-climatic condition - Atmospheric temperature and humidity affect the chemical composition of plants.
• Cultivation practices – seed rate, seed treatment, time of sowing, method of sowing, manure and fertilizer, irrigation, weeds and disease control influence growth rate and the chemical composition of plants.
• Stage of growth – The content of crude protein, soluble ash is higher just before flowering and goes down at seed formation stage, whereas crude fibre and dry matter content increase as the plant matures. Ether extract goes down progressively at maturity of the plant.
• Processing and preservation practices – Different processing methods may change particle size, particle shape, nutrient content and composition of plant materials.