Feed Analysis Methods PDF

FEED ANALYSIS Feeds are analyzed by (3) methods: 1- Physical evaluation:  Least accurate.  Provide a quick and easy result.  What are the characteristic features of good grains and other concentrates that can proved to the animal?  No splitting or cracking....

FEED ANALYSIS Feeds are analyzed by (3) methods: 1- Physical evaluation:  Least accurate.  Provide a quick and easy result.  What are the characteristic features of good grains and other concentrates that can proved to the animal?  No splitting or cracking.  Good colour and odor.  Free from rodent and insect damage, weevils, rancidity or foreign bodies (not more than 1%).  Can be examined by naked eye, microscope or telescope. 2- Biological evaluation:  Two types of biological evaluation: a- Microbial assays:  Micro-organisms require a nutrient in question and grow only when present. Unavailable nutrient → no growth. b- Nutrient deficient animal:  Animal fed a nutrient deficient diet then this nutrient is added and the growth rate is recorded. 3- 3- Chemical analysis of feedstuffs:  Sampling:  Samples should be taken from different places to represent all the container 17   Types of samples a- Dry (more than 88% DM): ground well and thoroughly mixed b- Green (less than 88% DM): cut to small parts as possible and partially dried at 60o C for 48 hrs. c- High fat content: preserved under cooling till analysis to prevent rancidity. METHODS OF ANALYSIS 1- Proximate chemical analysis:  Most widely used, developed by workers at the weende's experiment station in Germany because of laws that require listing of minimum and maximum amounts of components that may be present in commercial feed mixtures. By this method a feedstuff is portioned into six fractions: 1- Water 2- Crude protein 3- Ether extract 4- Ash 5-Crude fiber 6-Nitrogen free-extract. 2- Van soest analysis:  Used for determination and classification of crude fiber into: 1- Neutral-detergent fiber (NDF) 2- Acid-detergent fiber (ADF). 3- Acid-detergent lignin (ADL). 4- Hemicellulose 5- Cellulose. 18  PROXIMATE CHEMICAL ANALYSIS OF FEEDSUFFS I- Dry matter (DM):  Determination of moisture content (or dry matter) is the most common procedure carried out in nutrition laboratories.  The reason for this is:  To make analytical data are to be compared for different feeds.  To determine cost quality  To determine storage period  To estimate other nutrient (NFE)  After analysis, nutrient composition can be expressed on a dry basis or a normal as fed basis, which would be about 90 % dry matter for most grains. Determination of moisture content (or dry matter): 1- Weigh 5 g of fresh sample in a dried-weighed crucible or porcelain dish. 2- Put the crucible with its content in a hot air oven at 105 C for 3 hours. 3- Cool in a desicator and weigh. 4- Repeat drying and weighing till obtaining 2 constant successive constant weights. 5- The difference between weight of the crucible before and after drying is expressed as moisture content in 5 g sample. 6- Calculation: Weight before drying – Weight after drying Moisture % = X 100 Sample weight 19 Dry matter %= 100% - Moisture %. Weight after drying Or Dry matter %= x 100 Sample weight  Example: Weight of crucible = 42.600 g Weight of crucible + sample = 47.600 g Weight of crucible after dryness = 47.000 g Moisture content = 47.600 - 47.000 = 0.600 g 0.6 x 100 Moisture % = = 12 % 5 DM % = 100 – 12 = 88 %  Moisture percent of the different feed stuffs varies from 9 - 85 %, the lower for cereals and the upper for green fresh plants. II- Crude protein (CP):  The protein content of foods can be estimated from the nitrogen content.  Proteins contain, on average 16% N; hence crude protein (CP) is defined as N x 6.25.  Total nitrogen has traditionally been determined by the Kjeldahl procedure. Methods of estimating protein from nitrogen determination don't distinguish between protein and non-protein nitrogen (NPN) such as amides, ammonium salts, and urea. The CP analysis doesn't distinguish one form of N from another, thus we cannot tell if a feed mixture has urea or the highest quality of protein such as casein (from milk). In addition, nitrate N is not 20  converted to ammonium salts by this procedure so N in this form is not included.  Amino acid composition can be determined on hydrolysates by ion exchange or HPLC methods.  The analysis is accurate and repeatable but is relatively time-consuming and involves the use of hazardous chemicals. Determination of crude protein by Kjeldahl’s method:  Principle of the method: 1. Conversion of various nitrogenous compounds of the sample into ammonium sulfate (NH4SO4) by the action of conc. H2S04 (the number of nitrogen atoms in sample equals No. of ammonium sulfate molecules). 2. Decomposition of ammonium sulfate by 50% NaOH and collection of the liberated ammonia in a weak boric acid solution. 3. Titration of boric acid, with indicator, which contained liberated ammonia against N/10 H2S04 to determine the No. of N/10 H2S04.  Procedures: It is classified into 4 steps: 1- Digestion:  Weigh one g of dried sample and place in Kieldahl's flask with 8 g catalyst mixture (consists of, 96% unhydrous sod. Sulphate & 3.5% copper sulphate & 0.5 selenium dioxide).  Pour 20 ml of conc. H2S04 on the sample and mixture. 21   Heat under the flask till the mixture become transparent, and the mixture is called digested mixture. 2- Distillation:  Transfer the digested mixture to another Kjeldahl's flask, and then add 400 ml of distilled water + 75 ml NaOH 50%.  Connect the flask with condenser.  Apply heat was and receive the liberated ammonia in a conical flask contains 50 ml of boric acid with indicator (indicator is methyl red, bromocresol green).  This indicator in acid medium→ red colour. in alkaline medium→ greenish blue colour. 3- Titration:  Titrate the boric acid contained the liberated ammonia against N/10 H2S04 and determine the N/10 H2S04. 4- Calculation:  Each ml of N/10 H2S04 = 0.0014 g nitrogen.  Nitrogen % = No. of H2SO4 x O.0014 x 100.  CP% = nitrogen % x 6.25.  Example:  In an experiment for CP determination in a feed sample it is found that No. of ml N/10 H2S04 = 11.6 ml are consumed in titration. Calculate CP content of this sample.  Nitrogen = 11.6 x 0.0014 = 0.0162 g.  Nitrogen % = 0.0162 x 100 = 1.62%.  CP% = 1.62 x 6.25 = 10.12 %. 22   Examples:  Can molasses 2.9 %  CS hulls 3.9 %  CSM & soybeans 40 %  Grass 2.7 % (dry 14.4 %) III- Ether extract (EE):  The residue obtained when a feed sample, or other material, is continuously extracted (4–16 h) with ether; in the proximate analysis of foods it is a measure of crude fat content. Water-soluble substances may first be removed from the sample by extraction with several portions of water; the sample is then dried and continuously extracted, in a Soxhlet apparatus, with ether. The extract is weighed after evaporation of the ether.  Ether extract include the true fats and fatty acid esters, some of the compound lipids, and fat-soluble vitamins or provitamins such as the carotenoids.  The primary reason for obtaining some ether extract data is an attempt to isolate a fraction of feedstuffs that has high caloric value.  The lipid components can be further characterized by determining individual fatty acids from gas chromatography of their methyl esters (FAME-GC: fatty acid methyl esters) or by high-pressure liquid chromatography (HPLC) of intact triglycerides. 23 Determination of ether extract (Soxhelt method):  Principle of the method: - Extraction of the dried sample with ether (fat solvent) using soxhelt's apparatus.  Soxhelt's apparatus: 1. soxhelt's flask → for ether (at bottom). 2. Extraction part → for thimble (at middle). 3. Condenser part → for water current (at top).  Procedures:  Put 5 g of dried sample into a thimble.  Transfer the thimble and its content into Soxhelt apparatus then apply electrical heat for extraction for about 16 hours.  Remove the Soxhelt flask and dry in hot air oven at 105 oC for 3 hrs.  Cool in a desicator and weigh.  The increase in weight of Soxhelt flask represents the amount of the ether extract in the sample analyzed.  Calculate the ether extract % in the sample.  Example:  In an experiment for EE determination in a feed (5 g) sample, it's found that:  Weight of flask before extraction = 96.790 g  Weight of flask after extraction = 96.580 g  Calculate EE content of the feed sample.  Ether extracted in 5 g sample = 0.210 g  Percentage of ether extract = 0.21 x 100 = 4.2 %. 5 24 N.B. In the Weende's system the carbohydrate fraction was considered to consist of crude fiber and nitrogen-free extractives (mainly starch and simple sugars). IV- Crude fiber (CF):  Crude fiber in a feed includes cellulose, hemicellulose, lignin and the other carbohydrates which are so resistant and insoluble in weak acid and alkali.  Crude fiber is made up primarily of plant structural cell wall such as cellulose and hemicellulose, but it also contains some lignin, a highly indigestible material associated with the fibrous portion of plant tissues. For the monogastric animals, crude fiber is of a variable but low value, but is much more highly utilized than by monogastric. Determination of crude fiber (CF) “Using Weende Method”  Principle of the method:  After removing the water and extraction of the fatty material from a given sample of a feed substance, it's boiled (30 min.) with weak acid and then for the same period of time with weak alkali of the same strength to removes the starch, sugars and crude protein leaving behind, as a residue the crude fiber and ash.  The residue left after filteration, is dried, weighted and ignited.  The loss in weight after ignition is taken as the crude fiber weight. 25  Procedures: 1. Two g of dried, fat-free sample are placed in a conical flask (1L capacity) with 200 ml of 1.25% H2504 (vlv) and brought to boiling. 2. Electric heating is then applied (30 min.) while a reflex condenser is fixed, so that the volume of the mixture in the flask is kept constant. 3. Remove the flask and immediately filter through a suitable filter (e.g. linen-asbestos, nylon cloth) in a Buchner's funnel with the application of gentle suction. Wash with ml dist. boiling water until the washings are no longer acid. 4. The insoluble residue is transferred back into the conical flask by means of a washing squeeze bottle containing 200 ml of 1.25 % NaOH (w/v) brought to boiling. 5. Electric heating is applied (30 min.), the volume of the mixture should be kept constant by using a reflex condenser. Filtration by gentle suction, is carried out through Buchner’s funnel immediately 6. Wash the insoluble filtrate is with about 20-30 ml boiling dist. H20, and then by 1 % HCl. Finally wash the contents of the funnel with about 15-20 ml of 95 % alcohol followed by the same volume of ether in order to remove all traces of alkali. 7. Transfer the all insoluble filtrate into a crucible carefully by the aid of a washing-bottle containing dist. H20. 8. Dry the crucible contents in a hot-air oven at 105 0C / 3- 6 hours. Cool in a desicator and weigh 9. The crucible and its contents are placed into a muffle furnace and ignite at 550 oC (8 hours) Cool and weigh 26  The loss of wt. represents the amount of CF in the 2 g sample. The percentage of CF could then be calculated.  Example:  In an experiment for CF determination in a feed (2 g) sample, it's found that:  Weight of filtered dry sample = 0.8 g  Weight of residue remaining after burning = 0.2 g  Calculate CF content of the feed sample.  CF content = weight before burning - weight after burning = 0.8-0.2 = 0.6.  Percentage of ether extract = 0.6 x 100 = 30 %. 2 V- Ash:  Ash is the residue remaining after all the combustible material has been burned off in a Muffle furnace at 500 - 600 oC for 6-8 hrs until the ash is free from carbon.  Inorganic part of DM of feedstuffs.  It should be noted that some mineral elements, such as iodine and selenium, may be volatile and are lost on ashing.  Normally, these elements represent only every small percentages of the total, so little error is involved.  The ash content in cereal grains ranges from 1.5 to 4 %.  The hays and straws are higher in minerals than grains. Because of the accumulation of minerals in the leaves during growth, the soil washed upon the growing plants by rain, and to dust settling on the roughage.  Ash in fresh grass, silages and roots is low due to the high water content. 27 Determination of Ash: Advantage:  Nutritionally, ash values have little importance, although excessively high values may indicate contamination with soil or dilution of feedstuffs with such substances as salt and limestone.  Data on ash are required to calculate of carbohydrate (NFE) by difference.  Crude ash may enable a calculation of calcium and / or of phosphorus. Disadvantage:  The ash component of plant materials is highly variable, not only in total amount but in its parts.  Many feeds are high in silica, an element that is of no nutritional value.  In some types of feed the ash may be much over estimated because of adhering sand or mineral material of their nature, as for example, in pasture forage where soil has been splashed into the forage.  Procedures: 1. Five grams of sample are placed in a dry, clean and weighted crucible. 2. Sample and crucible are placed in Muffle furnace at 500 - 600 oC for 6-8 hrs. 3. Cool in desicator and weight. 4. Calculate the ash content.  Example:  In an experiment for ash determination in a feed (5 g) sample, it's found that: 28  Weight of crucible before ignition = 14 g Weight of crucible after ignition = 15 g  Calculate ash content of the feed sample.  Ash content =15 - 14 = 1.  Percentage of ash = 1 x 100 = 20 %. 5 VI- Nitrogen-Free-extract (NFE):  This term is misnomer in that no extract is involved.  It is determined by difference; that is, NFE is the difference between the original sample weight and the sum of weights of water, ether extract, crude protein, crude fiber, and ash. It's called nitrogen-free because it ordinarily would contain no nitrogen.  NFE % = 100 – (water % + CP% + EE% + CF% + Ash%).  NFE is made up primarily of readily available carbohydrate, such as the sugars and starches, but it may also contain some hemicellulose and lignin, particularly in such feedstuffs as forages.  Nutritionally, the NFE fraction of grains is well utilized by nearly all species, but NFE from forages and other roughages are less well utilized.  The accuracy of NFE measurement is questionable in that, being determined by difference, it includes the accumulated errors of other assays. It's not, in itself, an assay, but simply ‘what’s left’ 29 Limitations of Weende’s system of feed analysis:  The partition of carbohydrate into crude fiber (CF) and nitrogen free extract (NFE) is presumed to represent a separation of the more digestible (starch and sugars) from the less digestible (crude fiber).  However, in feeds listed in feed composition tables, the NFE is over estimated. This comes about for several reasons, the first of which is that CF method (successive boiling with dilute sulfuric acid and sodium hydroxide) doesn't recover all the fiber and large portions of fibrous constituents are extracted into the NFE.  The most important of these fractions are lignin and hemicellulose. Lignin is dissolved by sodium hydroxide and hemicellulose is dissolved by both acid and alkali. The basic error of the NFE concept is the assumption that if constituents are soluble they are digestible.  Lignin, the rigid component of wood, not only is indigestible but lowers the digestibility of substances with which it's associated. Van Soest system of partitioning forages:  The neutral detergent fiber (NDF) is representative of the fibrous constituents of cell wall and contains lignin, cellulose, hemicellulose and some protein bound to fiber bound protein.  That part of the sample not appearing as residue is termed Neutral Detergent Solubles (NDS) represent cell contents and contains lipids, sugars, organic acids, non-protein nitrogen, pectins, soluble protein and other water soluble matter. 30  Crude fiber contains most of the cellulose and only part of the lignin, so that Acid Detergent Fiber (ADF) values are about 30 % higher than those for crude fiber in the same feeds.  The acid detergent fiber (ADF) differs from the previously described Neutral Detergent Fiber (NDF), it represents the cellulose and lignin portion of the cell wall of plants.  The ADF analysis will be required for evaluating the quality of forage for ruminants and other fiber utilizing herbivores. For non-ruminants with little fiber utilizing capacity, the neutral detergent fiber will be the only fiber value required.  Classification I:  Plant material Cell wall Cell contents 1. Hemicellulose 1. Sugars, soluble carbohydrate, 2. Heat damaged starch protein 2. Pectin 3. Cellulose 3. Non-protein nitrogen 4. Lignin 4. Protein 5. Lipids 6. Other solubles 31 Classification II of forage fractions using the detergent fiber methods of Van Soest: Feed  Digest with neutral detergent solution (AD)   Neutral detergent solubles (NDS) Neutral detergent insoluble fiber (NDF) Cell content Cell wall  Digest with acid detergent solution (AD)   Acid detergent solubles (ADS) Acid detergent solubles (ADF) Hemicellulose, Heat damaged protein Cellulose, lignin Digest with 3% potassium permanganate Digest with 72% H2S04     Soluble Insoluble Soluble Insoluble (Lignin) (Cellulose) (Cellulose) (Lignin)   Cellulose by loss on ignition Lignin by loss on ignition 32