Introduction
The chemical composition of plant and animal represents all the physical” and chemical basis of protoplasm of the living processes, which occur in it. The animal body derives all the nutrients for its physiological functions from the digestion of plant and plant products with limited amount of animal origin feeds such as fish meal and milk.
50 a brief consideration of the chemical composition of the animal in relation to the composition of its food is useful to give a general picture of the nutritional process. We must know the chemical composition of farm animals to understand their nutrient requirement and composition of plants because they furnish most of the food for livestock.
Chemical composition of plants and animals: Plants and animals tissues are made up of similar type of chemical substances but their relative amounts are variable. Plants are analysed by proximate method of analysis given by Henneberg and 5tohmann (1861).
Whereas, animal body was first analysed by Lawes and Gilbert (1858) by slanghter experiments. Most of the nutrients present in plants and animals are arranged in to six groups, which are water, protein, carbohydrate, fat, mineral and vitamin. Plants and their by-products show much larger differences in the chemical composition than the animals.
Plants synthesize complex materials from simple substances such as carbondioxide, water, nitrates and other mineral salts from the soil and energy trapped from the sun by the process 13 Handbook of General Animal Nutrition of photosynthesis. The greater parts of the energy trapped as a chemical energy within the plant itself and the animals use this energy. Thus, plants store and animals dissipate energy
On fresh basis (as such basis): On as such basis means expressing the chemical composition of the feed as is fed to the animals. The advantage of this expression is that it helps in computation of ration
On dry matter basis: Chemical composition of feed stuffs is expressed on dry matter basis. The advantage of dry matter basis is that various feed stuffs can be compared among themselves by bringing at same standard unit of measurements. The average chemical composition in round figures of the common Indian feed stuffs is given in Table
Plant factor: There is a marked difference in the chemical composition between the different varieties of the same species of forage because of different genetic material.
Agro-climatic condition: When a forage plant is exposed to variable agro-climatic conditions it shows variable growth performance, which directly reflects the chemical composition. The factors like atmospheric temperature and humidity affect the chemical composition of plants.
Cultivation practices: The cultivated forages, under the same agro-climatic conditions perform in different ways depending on the cultivation practices. The seed rate, seed treatment, time of sowing, method of sowing, manure and fertilizer, irrigation, weeds and disease control measures not only influence the growth and yield of the forages but also chemical composition.
Stage of growth: There is a relationship between the stage of growth of the plants and its chemical composition. The content of crude protein, soluble ash, phosphorus and potash is higher just before flowering and goes down at bloom and seed formation stage whereas, crude fibre and dry matter content increase as the plant matures. Ether extract goes down with the progressive maturity of the plant.
Processing and preservation practices: The changes in chemical composition of plants are very much influenced by method of processing and preservation. Different processing methods may change particle size, particle shape, nutrient contents and also composition of plant materials.
Biochemical basis of soil, plant and animal: The plant synthesized their feed from CO2 and H2 0 in the presence of sunlight and chlorophyll in the form of carbohydrates, which is structural as well as storage component of plants. They absorb minerals (Inorganic component) as well as water from soil and precede various biochemical reactions in plant body. Many factors like applicati0n of manures and fertilizers, irrigation, stage of growth, frequency of cutting, type of variety and strain and soil composition affect the chemical composition of the plant. As the composition of soil changes, it also affects composition of plants.
