ANIMAL NUTRITION
Definition
Animal nutrition could be defined in practical terms as the science of nourishing the body. It could be summarised as the reactions within living organisms which provide the materials necessary for producing energy, growth and the maintenance of health, stimulation of various secretions, storage and for the maintenance of internal osmotic and pH balances.
Farm animals need a regular supply of food to ensure a healthy and productive life. Animals require food to supply energy for movement and for maintenance of body temperature, as well as for growth of their skeletons, muscles or flesh, hair etc. Healthy animals will produce meat, milk, eggs and fat of an excellent quality for human needs.
Animal nutrition deals with the nature and properties of substances which can serve as animal feeds, the proportions in which these substances must be made available to farm animals, and the mechanisms through which these substances are converted into animal tissues and products. Most substances useful to animals as food come from plants.
Animal feeds can be classified either on the basis of their source of derivation, their physical characteristics, the nutrients they contain, or on a combination of all these factors. Here, a method of classification which is based on the usefulness of the feed component in a feed ration to the animal body will be presented for study. The proportion of different types of feeds given daily by the farmer to his animals is referred to as a ration.
The nutritional requirements of animals can be broadly classified into organic compounds and inorganic substances. The organic compounds are represented by carbohydrates, proteins, fats and vitamins which are required for growth, repair, respiration, secretion and storage. The inorganic substances are mainly mineral salts and water which are needed to maintain ionic, osmotic and pH balances within the body. Nutrition in animals entails digestion, absorption, distribution and assimilation of various food substances.
Classification of Animal Feeds
There are various types of feeding stuffs available for livestock feeding. These feeding stuffs can be grouped into different classes on the basis of bulkiness and chemical composition. Though strictly speaking no two feeding stuffs are alike in the composition and characteristic but in practical feeding, substitution of one feeding stuff is made with another depending upon the market price and availability in a particular region.
Animal feeds can be classified according to the quantity of fibre and moisture in the feed into four main groups. They are:
(a) Basal feeds
(b) Roughages (silage, hay and straw)
(c) Supplements
(d) Concentrates
The schematic representation of the classification of feeding stuffs has been shown in the table below.
Feeding Stuffs
Feeding stuffs
Roughages
Dry roughages: straw, hays, etc.
Green roughages
Leguminous: berseem, lucerne, cowpea, etc.
Non-leguminous: maize, sorghum, barja, etc.
Concentrates
Animal sources: fish meal, meat meals, etc.
Vegetable sources
Grains: maize, barley, etc.
Oil cakes: GNC, Til cake, etc.
By-products: brans and chunnies.
Additives
Vitamin supplements
Mineral supplements
Antibiotics
Anabolics
(a) Basal (energy) feeds: These are mostly easily digestible carbohydrates with low protein content. They constitute 60-90% of practical livestock rations. They have low fibre content and thus need to be supplemented by high protein feeds. Are highly acceptable to most farm animals especially those which are monogastric. Energy foods include cereals - maize, rice, millet, guinea corn or roots and tubers such as yams and cassava. Such foods lack vitamins, and important minerals like calcium and phosphorus and generally require supplementation to meet maintenance and growth requirements of livestock.
Supplements: are feeds given to make up for any shortages in the diet or to supply a deficient nutrient. They can be fed either in a mixture with basal feeds or separately. They are usually rich in protein and may contain vitamins and minerals. They include such protein-rich materials as fish meal, blood meal, milk by-products, groundnut cake, cotton seed. The animal based materials are also rich in minerals.
Concentrates: are feeds or feed mixtures providing all the primary dietary needs of protein, carbohydrates, fats and some minerals. Concentrates in feed industry refers to artificial feed mixtures such as groundnut cake (GNC) mixed with blood meal. It may be either whole grain feeds or mixtures of basal and supplement feeds. The best known concentrates in use include groundnut cake, cotton seed meal, palm kernel cake (PKC) and coconut meal are good for protein, phosphorus and energy but lack some vitamins. Groundnut cake, for example, contains twice as much protein when decorticated than when it is undecorticated that is when it is mixed with part of the husk from the fruit.
Roughages are rich in plant fibres which provide a bulk fodder, useful in grazing animals which gain it from hay, maize stems, green pasture. These feeds can be given either dry, in the form of hay, straw (mature grass), seeds hulls or maize stems; or wet, as green pasture or cut and chopped green feed. Wet roughage is sometimes referred to as _succulent feed_.
Succulent feeds have high water content. They are easily digested. Examples are green grass, pumpkin, silage and most green crops When green grass is cut and stored in a pit or a silo it turns into an acid vegetable mass called silage. Roughage in the form of pasture, dried grass and silage is the cheapest form of feed for cattle, sheep, and goats. Animal fed on roughages need supplementation if the animal is to do well especially if it is to produce milk.
(b) Animal protein concentrates: Typified by fishmeal, blood meal, bone meal are high in protein and their excellent mineral content. These by-products are obtained from slaughtered animals and their carcasses. Meat not good for human consumption is dried and ground into meat meal while carcasses of dead animals are processed into meat or bone meal. These concentrates are fed in small quantities to make good deficiencies of some of the essential amino acids in poultry and pigs. In addition they supply vitamins of B-group and minerals. Different animals require different types of food. E.g. cattle and sheep require food that contains large amount of fibre. Pig and poultry require concentrate foods that are low in fibre. Young, and growing animals need a larger quantity of proteins than mature animals.
Straw and stover: These are the vegetative remains of cereal crops collected after harvest. Harvesting is done after the crops had reached full maturity and fruits and seeds removed and were almost dying. They have high fibre, low protein, carbohydrates, vitamins and mineral contents. These materials are collected, stacked and rationed out as feed to livestock.
Hay: Hay making involves the cutting, drying and bailing of grasses and legumes, and mowing and bailing machines have been specifically designed for these operations. It is the most profitable method of preserving high quality forage for future use. The objective of hay making is to reduce moisture in green forage crops to a sufficient degree so that they can be stored without fear of fermentation losses or spoilage due to mould growth. In that process the endeavour should be to preserve the maximum amount of nutrients possible. The stage of maturity of the crop at the time of cutting is very important as far as crop nutritive value of hay is concerned.
Silage: Silage can be called the fermented product of forage crops where the acids produced by anaerobic fermentation of the sugars present in these forage preserve them. It supplies more nutrients than hay. Best grass silage is made when the material has 60-75% moisture content. The chopped grass is packed in trenches or silos and pressed firmly to exclude air, then covered with soil and polythene bags. The low moisture content of the plant materials facilitates fermentation. Good silage should have a mild, pleasant aroma, an acid taste and slightly greenish colour. It should be free from sliminess and mould growth and should have sufficient acid to prevent degradation.
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