Preface There are several textbooks on Theoretical aspect of Animal Nutrition written by eminent scientists. But no single textbook is their till the date regarding the practical courses of the subject for undergraduate students of Veterinary science by providing all the needed information at single place. As per the Veterinary Council of India regulations now Animal Nutrition course has been redesigned into three courses for the first three semesters of the degree and including the courses on Principles of Animal Nutrition and Feed Technology (ANN-111), Applied Animal Nutrition-I (ANN-121), dealing with ruminants animals and last on is Applied Animal Nutrition-II (ANN-211), deals with Non-ruminants animals. As per the new VCI syllabus the book covers all the three courses in three different parts with different chapters covering all the topics of the practical.

Livestock feeds are generally classified according to the amount of a specific nutrient they furnish in the ration. They are divided into two general classes roughages and concentrates. Roughages are bulky feeds containing relatively large amount of less digestible material, i.e. crude fiber more than 18% and lower than 60% TDN on dry matter basis. Concentrates are feeds which contain relatively smaller amount (less than 18%) of fiber and have comparatively high digestibility and as a result higher nutritive value having more than 60% TDN. A. Roughages Roughages are subdivided into two major groups – succulent and dry, based upon the moisture content. Succulent feeds usually contain moisture content from 60 to 90%, whereas dry contains only 10 to 15% moisture. Succulent may again be divided into pasture, cultivated fodder crops, tree leaves, silage and root crops. Dry roughages may be further classified as hay and straw based on the nutritive value and methods of preservation.

The procedure used in the preparation of samples depends on the purpose of analysis and the nature of the constituents that are to be determined. a. Plant material (Herbage)     1.    Separate the plant material by using sharp knife.     2.    Remove the contaminations like soil or other material by gentle brushing. Never wash the plant material with water.     3.    Mix corresponding plant parts from more than one plant to obtain representative sample of sufficient size for analysis.     4.    Cut the sample immediately into small pieces and mix thoroughly.      5.    Weigh a portion of this sample for those analyses which are to be performed on green material.      6.    Dry the sample in a hot air oven at 100 ± 2ºC for storage.

Two German scientists Henneberg and Stohmann working at the Weende Experimental Station, Germany devised proximate principles analysis system in 1860’s for routine description of animal feedstuffs. Therefore this system is also known as Weende system of analysis. Proximate analysis is a system of expressing the nutrient composition of a feed. The principle of analysis is to separate the nutrient present in the feedstuffs into various fractions, as proximate principles, which are six i.e. moisture, ash, crude protein, ether extract, crude fibre and nitrogen free extract. Water (Moisture) The moisture is determined as the loss in weight which results from drying a known weight of feed to constant weight at 100°C. Therefore, dry matter is estimated as a part of substance that does not evaporate at 100°C. The major difference in nutritional value on as fed basis is traceable to moisture content and dry matter. Calculation of relative cost of nutritional value involves consideration of moisture content.

Principle If a sample of feed is heated and dried in a hot air oven at the temperature of boiling water (100°C ± 2°C), the water present in feed sample escapes as vapour. The loss in weight is considered as moisture and the residue is termed as dry matter (DM). Requirement     1.    Aluminium/steel moisture cup or Iron trey     2.     Analytical balance     3.     Dessicator     4.     Hot air oven     5.     Metal tongs     6.     Spatula

Principle Total ash is the inorganic residue which remains after a feed stuff is ignited to carbon free at 550-600oC in a muffle furnace. In other words, ash is that part of the material which does not disappear at 550-600ºC, while all the organic matter (OM) gets burnet. Requirement     1.    Analytical balance     2.     Asbestos sheet     3.     Dessicator     4.     Heater /gas flame burner     5.     Metal tongs     6.     Muffle furnace     7.     Silica basin/crucibles

Principle The portion of the total ash which is insoluble in dilute hydrochloric acid is called acid insoluble ash (AlA) and it is the part of ash which is having unavailable mineral matter like silica and sand. Silica is the part of mature plant materials which are highly lignified or woody like straw, husk, stems and stalks, while sand inters in feeds by faulty handling in the fields or as an adulterant. Equipment/glass wares     1.    Asbestos sheet     2.     Filter paper (Whatman No.1)     3.    Funnel stand     4.    Glass funnel     5.     Glass rod     6.     Hot plate/heater/Bunsen flame     7.     Metal tongs     8.     Silica basin (crucible)     9.     Volumetric flask     10.     Wash bottle with distilled water

Principle Crude protein constitutes a mixture of true protein and non protein nitrogenous substances and is determined by estimating nitrogen and then multiplying the nitrogen content of feed by the factor 6.25. The factor 6.25 is derived on the basis that all proteins contain 16% nitrogen. The total nitrogen content in the feedstuff is determined by Kjeldahl method which generally consists of three steps, i.e. digestion, distillation and titration. The sample is digested with an excess quantity of concentrated sulphuric acid which hydrolyses the protein, decomposes to ammonia and finally the ammonia combines with the excess of sulphuric acid forming ammonium sulphate. The acid digest is cooled, diluted with distilled water and distilled with strong alkali (sodium hydroxide, 40 per cent), the ammonia released during distillation is taken up into a boric acid solution forming ammonium borate complex and such ammonia is titrated with standard sulphuric acid. While estimating the nitrogen content, following reactions take place:

Principle When a sample of feed, which is free from moisture, is extracted continuously with fat solvent like petroleum ether, the vapour from the ether boiling in the flask passes into the condenser where it condenses and drops back on the sample which dissolves ether soluble materials such as fat, sterols, lecithin, resins and volatile oils in the extraction flask. The extract is termed as crude fat or ether extract (EE) because it also contains other fat like substances in addition to true fat. Equipment/glass wares     1.     Analytical balance     2.     Beaker     3.     Cotton wool     4.     Dessicator     5.     Extraction thimble     6.     Hot air oven     7.     Oil flask (150-250 ml)

Principle When a sample of moisture and fat free feedstuff is boiled with dilute acid and then with dilute alkali, the soluble carbohydrates and proteins go into the solution and are extracted. The undissolved residue left behind represents cellulose, hemicellulose, lignin and mineral matter. The cellulose, hemicellulose and lignin put together are called crude fibre (CF). When the residue after drying and weighing is ignited, the fibre being organic in nature is burnt whereas the ash or mineral matter is left over. The fibre is obtained by deducting the weight of ash from the weight of the dried residue. In simple way it can also be explained that the crude fibre is determined gravimetrically as part of the substance which is left when protein, soluble carbohydrate, fat, ash and water have been removed. In feeding of simple stomached animals, the analysis of crude fibre content is very essential because the amount of crude fibre predicts the digestibility of the feedstuff. Higher the fibre content lesser will be the digestibility.

Principle Carbohydrates are divided into two groups i.e., crude fibre (CF) and nitrogen free extractives (NFE). The NFE comprises the sugars, starch and a large part of the material classed as hemicellulose. The NFE is not determined by analytical procedures. This is calculated as the figure obtained when the sum of water, ash, protein, fat and crude fibre of a feed is subtracted from 100. Since the figure is determined by difference, it includes the cumulative errors of the other determinations and thus it is not an exact value. Requirement Following analysed volumes of a feedstuff are very much essential to derive the nitrogen free extractives of the same feedstuff. Calculation The nitrogen free extractives can be derived from the following formula:

Principle When a solution containing calcium is treated with ammonium oxalate, all the calcium present is precipitated as calcium oxalate. The precipitate when dissolves in sulphuric acid, forming calcium sulphate and liberating free oxalic acid which is quantitatively estimated by titration against standard N/10 KMnO4 to arrive at the calcium content present in the given solution. Following chemical reactions takes place in the estimation of calcium:

Principle Phosphorus is the chief acid forming mineral constituent of plant and feeds. Phosphorus present in the ash solution (Mineral extract) is precipitated as ammonium phosphomolybedate. The precipitate is washed with dilute potassium nitrate till free from acid and dissolved in a known excess of standard sodium hydroxide solution. The excess alkali is back titrated against standard acid to arrive at the exact quantity of standard solution required.

To overcome the limitation of proximate analysis P.J. Van Soest in 1963 developed a method which makes use of the concept that the dry matter of plant origin consists of two principal parts:     1.    Cell contents      2.    Cell wall contents The method is efficient to take care of the defects in the principle of estimating crude fiber and NFE by proximate analysis. Van Soest has partitioned the carbohydrates into various fractions by a system of analysis using detergents. Cell contents are soluble in neutral detergent includes lipids, sugars, organic acids, starch, soluble proteins, NPN compounds and other water soluble materials, where as cell wall (fiber) is insoluble in neutral detergent but it is soluble in acid detergent includes hemicelluloses, cellulose, lignin, lignified nitrogen compounds, heat damages proteins, keratins and silica. This method of partitioning carbohydrate is essential to be expressed in case of ruminants, due to their capacities for making use of different fractions of crude fibre especially the cellulose and hemicellulose, while the simple stomached animals can rarely do so. 

The undesirable constituents includes the toxicants and other adulterants in the feed which are not suppose to be there in the feed and presence of these substances either make the nutrients of feed less utilizable or even the feed become toxic for consumption by animals. Hence it is very essential to find out the presence and also the amount of that substances on which basis decision may be made that the particular feed stuff or ingredient is safe to be consume by the livestock or that has to be rejected. The common undesirable constituents of the feeds are given below in detail:

Silage is the green material produced by controlled anaerobic fermentation of the green succulent fodder crop retaining its moisture content. The process of preparing silage is known as Ensiling and the pit in which silage is prepared is called silo. Crops suitable for silage making The fundamental behind the conservation of fodder as silage is the acidic condition, which is produced by the anaerobic fermentation of carbohydrates rich fodder. Thus the necessity of the fodder crop being used for silage preparation is the presence of high amount of fermentable carbohydrates and the natural carbohydrate rich crops are the cereal crops like maize, jowar or bajra and grasses or their combination in 3:1 with leguminous crops. Otherwise high moisture leguminous crop after wilting in combination of molasses may be  used.

Proximate analysis of the feeds and fodders does not give any idea about their nutritive value, because availability of nutrients varies according to the feed stuffs. The major loss of nutrients take place in body after ingestion of feed is through feces. Hence, it is very essential to know the actual amount of feed digested by the animals. Losses which take place after digestion are more or less comparable in different feedstuffs. Digestibility Digestibility of a feed can be defined as that proportion of feed which is not being excreted in the faeces and hence assumed to be absorbed by the animal. It is expressed as percentage (% digestibility or digestibility coefficient).

Digestion trial requires feaces collection only but when we have to go for balance studies we have to collect urine also (in addition to the nutrient losses take place through milk in lactating animals) to find out the nutrient losses takes place through urine. As we have discussed in digestion trial also, male animals are usually preferred to perform these types of studies to obtain contamination free urine and feaces to find out clear picture. Balance studies are usually performed to find out the balance of nitrogen (Nitrogen retention, NR) and minerals (Ca, P etc.) as urine is rich in these nutrients and hence for their balance we have to find out the losses takes place through urine.

The nutritive value of feedstuffs is generally expressed in terms of protein and energy value. The protein and energy value usually referred in ruminants are DCP (Digestible crude protein) and TDN (Total digestible nutrients), because the feeds used in the diet of ruminants have a vide variability in their digestibility, hence after removal of the variable fraction the requirement of nutrients is expressed. Starch Equivalent (SE) is also the measure of energy but its usefulness is limited to certain extent, due to involvement of tedious and expensive process.

It is very essential to know the nutritive value of common feedstuffs used in the diet of ruminants. On the basis of these values the nutrient requirements of ruminants may be fulfilled for different body functions like maintenance, growth, lactation, wool production or others. The nutritive value of various common feedstuffs used in the diet of ruminants is being presented in the table below:

When we are having two or more than two feed ingredients and by using them we have to prepare a mixture of desired nutrient composition then we will require to use Pearson’s square method. Use of pearson’s square is a simple procedure that allows us to mix two feed stuffs with different nutrients concentrations and come up with a mixture of the desired total concentration. For the pearson’s square to work, the desired diet’ nutrient concentration must be between the nutrient concentrations of the two feed stuffs. Suppose we have a protein source such as ground nut cake (GNC) with 40.9% crude protein (CP) and maize with 8.8% CP, and we need a mixture of the two that will have 18% CP. AS shown in the illustration, we compare the CP percentage of each feed on the left with the desired percentage in the middle of the square. The lesser value is subtracted from the greater value and the answer, in parts of a mixture rather then in percentage, is recorded diagonally, but read horizontally.

Nutrient requirements of the animals in terms of protein, energy, minerals and vitamins are the basis for scientific feeding. The total requirement of an animal includes two components (i) maintenance (ii) production. While maintenance requirement varies with body size of the animal, the requirement for production depends upon its physiological state and production levels. Such recommendations are based on the results of a large number of feeding experiments, conducted throughout the world. Feeding standards developed by Nation Research Council (NRC) of USA and Agricultural Research Council (ARC) of UK, for livestock and poultry are considered to be the best general guides for computation of ration. However, limited investigations carried out in this country suggest that adoption of foreign standards always leaves a fair margin of safety so far as the feeding of Indian species are concerned. This owes mainly due to differences in size, breed, nutritional values of feeding stuffs and other practices in the agro-climatic conditions of this tropical country. Some efforts have been made by India scientists in this area.

The formulation of ration for various categories of livestock depends upon the nutrient requirements for a particular animal or group of animals and the feeds and fodders available for the purpose. Livestock feeds can be grouped into two major categories – Roughages and concentrates, on the basis of bulkiness and chemical composition and combination of both is essential for a balanced ration. Roughages are the bulky feeds having crude fiber more than 18% and TDN less than 60% while, Concentrates are feed or feed mixture having crude fiber less than 18% and TDN more than 60%. They are rich in either energy or protein and accordingly are called as energy concentrates (when CP is less than 18%) or protein concentrates (when CP value exceeds 18%). Various energy concentrates are grains and seeds (maize, barley, sorghum etc.), milling byproducts (brans and chunis), roots (tapioca tubers, turnip, potatoes) and molasses.

Indian breeds of sheep have much lower adult weight (30-40kg) and growth rate in comparison to many foreign sheep breeds (70kg). Hence the requirements are lesser then foreign breeds. 1. Nutrient requirements for maintenance On the basis of several balance studies and digestibility trials the requirements for Indian sheep breeds has been developed and calculations are made on the basis of 2.73 g of DCP per kg of metabolic body weight and TDN and ME requirements are 27.3 g and 98 Kcal per kg of metabolic body weight respectively. The requirements for different body weight are given in the table below:

Goats are valued as economical milk producer and main source for meat for a large section of population. The dry matter intake varies from 3% (Meat goat) to 4-6% (Dairy goat) in different breeds of India and it is higher than that of larger farm animals. 1. Nutrient requirements for maintenance Adult body weight of goats may vary from 15 to 45 kg in different breeds. There are also does and bucks that weight up to 60kg. Nutrient requirements for maintenance of adult goats are, therefore given for body weights ranging from 15 to 60 kg. On an average for maintenance 76 g DM is required for each kg of metabolic body weight and similarly the requirements for DCP and TDN is 3 and 30 g, respectively. 2. Nutrient requirements for pregnant does Since adult body weight as indicated already varies from 15 to 60 kg, the requirements for pregnant does are also given for body weights ranging from 15 to 60 kg.

Poor quality roughages includes the wheat straw, commonly fed to ruminants but unable to provide any DCP. Urea ammoniation method, not only improves the nutritive value of straw in terms of DCP and TDN, but it also improves the dry matter intake of animal by improving its palatability. In this method of urea ammoniation, one quintal of wheat straw is treated with 4 kg fertilizer grade urea (4%) by dissolving in 40 litre of water (moisture 40%). The dissolved urea is sprayed over several layers of wheat straw and mixed properly and then kept under airtight condition by covering it with polythene sheet for a period of 4 weeks. With the presence of enzyme urease the urea get broken down in to ammonia and carbon di oxide. This ammonia on one hand improves the nitrogen content of the straw and on another hand alkalinity (by ammonia and by ammonium hydroxide) reacts on the lingo-cellulosic bonds to loosen their strength. So by increasing the nitrogen content of the straw it increase the nutritive value of the straw in terms of increasing the DCP value of the straw and on another hand by reducing the bonds of lingo-cellulose it increase the digestibility of crude fiber and hence it also increase the energy (TDN) content of the straw.

In the cases of drought and flood when the feed resources made unavailable, creates the problem of animals feeding. In those cases unconventional methods and materials will have to be used to fulfil the hunger and nutrient requirements of animals to sustain them.  Traditional methods of feeding     1.    Use of by-products of commercial crops such as oil seed crops, grams etc. as well as drought resistant vegetation in combination with NPN source and molasses (as source of energy) for meeting the immediate nutritional requirements.     2.     Certain varieties of tree leaves and extractions of inedible oil seeds can be used to meet the essential requirements of intact protein in ruminants. This proved to be successful during draught in many parts of India.       3.    Large scale feeding of bagasse and molasses in combination with urea and mineral supplements may be adopted without any toxic effects. Some of the daily ration schedule that has been successfully tried is given below:

Pigs are highly prolific among meat producing livestock and also excellent to all other type of farm animals in the efficiency of converting feed into high quality pork. The Nutrient requirements expressed for the mono-gastric animals like poultry and pigs as percent of the diet or the amount per kg of the diet, since they are generally fed in groups rather than individual feeding practiced in case of cattle and buffaloes (where absolute requirements are given). The latest requirements available are NRC nutrient requirements for swine, 1998 (10th revised edition), BIS, 1986 specifications for pig feeds and ICAR, 1998 for growing and finishing swine. Similarly ARC requirements are also available. NRC requirements are on 90% DM basis and are for breeds like Large White Yorkshire, Landrace, Berkshire etc., while BIS specifications are on 100% DM basis and for indigenous pigs, improved pigs and crossbred pigs.

The requirements for a given nutrient is the minimum quantity of that nutrient that will maintain normal growth and reproduction, when all other nutrients are supplied in adequate quantities and at the same time, prevent the development of symptoms of nutritional deficiency.   The accurate way to express the nutrient requirements is in amount per day per animal. Poultry are fed in groups and hence, it is not practicable to express the requirements in amounts per day per animal. So, they are expressed in relation to energy content of the diet as poultry eats within limits to satisfy their energy needs. However, the estimation of energy content of the diet is not possible on routine basis and the calculated values may very much from estimated values. Because of these difficulties, the nutrient requirements of poultry are expressed on unit weight basis. 

Complete feed system is a system of ruminants feeding in which roughage and concentrate mixture are mixed homogenously in a predetermined ratio and processed in to pellet, briquette or block form to provide the animals a nutritionally balanced diet. Complete feed system is advantageous over conventional feed system as it reduces the cost of labour, transportation and storage of feed, besides ensuring uniform supply of nutrients and maintaining the optimum rumen environment due to the constant dietary roughage: concentrate ratio, which also avoids the selective feeding.

Suggested Readings Anonymous, 1974. Laboratory Manual for Principles of Animal Nutrition.  Animal Science Department, College of Veterinary Science, Tirupati. AOAC 1995. Official Methods of Analysis. 16th Edn., Association of Official Analytical Chemists, Washington, DC 20094. Banerjee, G. C. 1988. Feeds and principles of Animal Nutrition 1st Revised edition, Oxford & IBH Publishing Co. Pvt. Ltd., New Delhi. Datt, C., Niranjan, M. and Singh N. P. 2006. Analytical Techniques in Animal Nutrition. Kalyani Publishers, New Delhi- 110002.  Gupta, P. C., Khatta, V. K. and Mandal, A. B. 1992. Analytical Techniques in Animal Nutrition. Directorate of Publications. CCS HAU, Hisar 125004, Haryana. IS: 6874 (Part I). 1970. Indian Standards. Methods of Tests for Animal Feeds and Feeding stuffs. Part I. General Methods, Indian Standards Institute, New Delhi-110002. ISI: 1992. Indian Standards Institution (IS: 13- 74). Poultry Feed Specification. Narahari, D. 2000: Field Methods of Feed Quality Control. Technical Bulletin. American Soybean Association. Pathak, N. N., Kamra, D. N., Agarwal, N. and Jakhmola, R. C. 1996. Analytical Techniques in Animal Nutrition Research. International Book Distributing Co., Lucknow, India.