Animal nutrition chapter 3
Describe some of the "additional" uses for the Van Soest system
-ADF is an indicator of forage digestibility because there is a high negative correlation between digestibility and ADF. Heat damage caused by improper ensiling of forages reduces the feed value of the forage. This is especially true of the protein. A large percentage of the feed protein can be tied up and rendered unavailable Heat damage can be determined rather precisely by acid detergent insoluble nitrogen (ADIN) method. The forage is analyzed for ADF, total N and N in the ADF (both by Kjedahl) The nitrogen found to be a part of the ADIN fraction is subtracted from the total protein content (total N) to determine the amount of protein actually available to the animal.
This lesson gives information on many methods of feedstuff analysis. No single producer will have need to analyze samples of all their feedstuffs using all tests discussed in this unit. Give 10 reasons to support this statement. Number your answers and put them in list format so they are easy for me to read. The answers to this question are found throughout the assigned materials.
-Cost of using all test for feedstuff analysis would be too high for most producers thus only the most important feedstuff analysis is used -Analysis of certain nutrients such as calcium content in grains is low and variability unimportant thus do not need to be used routinely. -Crude protein proximate analysis is not accurate or effective for non ruminant species. -Crude fiber proximate analysis holds low feed value for non-ruminant species thus should not be used for those species and is a tedious procedure. -Ether extract proximate analysis approach is effective only if the ether extract is made up primarily of fats and fatty acid esters. However, if the ether extract contains large amounts of plant waxes, essential oils, resins, or similar compounds it will not have much feed value to animals and thus would not be an effective approach. -Nitrogen-free extract approach is not well utilized for forages and roughages thus other approaches such as Van Soest analysis may be better to use. -Neutral detergent extraction is more effective in ruminant species rather than other species -Acid detergent extraction can be substituted by crude fiber method for ruminant species because it is more repeatable and faster. pH of feedstuff is used for fermented material and rarely used otherwise -Chemical methods are being replaced for amino acid analysis by modern semi automated equipment that can separate and measure individual amino acids in a relatively short time.
What are the limitations of the NFE and CF?
-The proximate scheme has limitations, especially with the crude fiber and NFE fractions. Sometimes NFE is less digestible than CF. -Low digestibility of the NFE is because hemicellulose and some lignin are dissolved in the weak acid and alkali, both of which are used in the CF determination. Both are poorly digested and thus skew the digestibility of the NFE. Because of this problem, predicting nutritive value from proximate analysis is a problem, especially for forages. It is mainly utilized for grain for all species. -CF not utilized for nonruminants as much as it is for ruminant species and is a tedious procedure.
Crude fiber
-obtained using ether extracted sample boiling it in dilute acid, then boiling in dilute base, filter, dry, burn in furnace and take difference between before and after burning is the crude fiber fraction. Made up of plant structural carbohydrates such as cellulose and hemicellulose and contains some lignin
Why is chemical analysis not necessarily the best predictor of the feeding value of forage?
Chemical analysis gives a broad appraisal of nutritive value of feeds. They do not give a direct index of feed value because digestibility of nutrients is not determined. Thus limiting the usefulness of chemical analysis to accurately predict the feeding value of a forage. Therefore, information about maturity at harvest, and storage conditions may be more valuable in determining forage value than chemical analysis (OTHER THAN MOISTURE).
What are the three types of analytical methods for determining nutrient composition?
Chemical procedures, biological procedures, and microbiological procedures.
Why were the Van Soest methods of forage analysis (Detergent Extraction Methods) developed?
Developed as a better means of better analyzing forages than the NFE-CF scheme i.e Nitrogen free extract and crude fiber
What are the nutrients of primary concern in cattle feeding?
Energy (carbs/fats), protein, calcium, phosphorus, vitamin A, and some trace minerals. Also the variability in content and cost of analysis relative to the cost of supplementation of a nutrient must be considered.
How is heat damage to forage predicted with Van Soest analysis?
Feed value of a forage is reduced significantly by heat damage because it decreases the availability of what can be digested (especially proteins). The negative correlation between digestibility and acid detergent fiber (ADF) makes it a good indicator for forage digestibility. Thus, San Voest analysis uses acid detergent insoluble nitrogen (ADIN) method to determine heat damage by analyzing ADF, total nitrogen (N), and N in ADF. Nitrogen that is part of the ADIN fraction is subtracted from the total protein content (i.e. total nitrogen) to find the amount of protein available for digestion.
Fodder
Food, especially dried hay or feed, for cattle and other livestock
Describe how to properly sample grain.
For grain and mixed feeds, sampling with a grain probe is most convenient and most accurate method of obtaining samples. A minimum of 5 cores should be taken from various places in the bin or truck. These should be mixed thoroughly in a clean container. Then take about a pint of the mix for a final sample.
What additional reasons might a large cattle feeder have for analyzing grain but not forage?
For large cattle feeder, grain analyses are more useful than forage analyses for two additional reasons: more grain is fed and grain is easier to sample accurately
Describe how to properly sample hay.
Hay can be sampled most accurately by the use of a forage sampler. Take enough samples to fill a half-gallon plastic bag. For hay bales, take core samples from the ends of bales. For loose or chopped hay, take samples from random locations of the pile(s) or stack(s). Samples will be easier to take with the sampler in the vertical position.
How do you properly sample wet material?
If feed sample is a wet material, seal in plastic bag immediately and freeze if possible
What are the reasons for evaluating the nutritive value of feedstuffs?
It is designed to evaluate nutrient composition, palatability, digestibility, productive value, and physical or handling characteristics, and can be used to make economic comparisons. It can also be useful in improving feed harvesting methods so the highest quality feed for the animals obtain will yield the most profit.
Describe how to properly sample silage.
It may be necessary to sample the silage several times during the feeding period. This is especially true if there is appreciable variation in the maturity, variety, or date of cutting of the silage when harvested. In silos that have been opened, take 15 or more double handfuls of silage from different locations, mix thoroughly and then take about one-half gallon for analysis. In tower silos with mechanical unloaders, take samples as the silage is being unloaded. Should samples be desired before silos are opened , dig into the top of the silo at 4 or 5 locations. Spoiled and discolored silage should not be included.
Why is it so important to determine the moisture content of feeds before mixing them into rations?
Moisture affects feed value and nutrient content more than any other component. It is not expensive to determine and when using a number of feeds of high moisture content such as feeders do today, moisture determination is almost a necessity in PROPERLY FORMULATING RATIONS and in buying or selling feed.
Why is proper sampling procedure for feed testing so important?
Proper sampling procedures are necessary if analyses are to be meaningful and useful. Inaccurate sampling procedures may lead to greater error than average analyses found in analysis tables.
Give a flow diagram for the Van Soest analysis of forage. What are all the uses of the Van Soest system?
Refer to flow diagram
Describe how to properly sample rations.
Sampling of the complete ration as it goes into the feed bunk can be useful in checking accuracy of ration formulation and/or uniformity of mixing. Ten or more grab samples should be taken as the feed is being unloaded in the bunk rather than picking up samples from the bunk.
How is feed intake predicted using Van soest analysis?
Van Soest system extracts components of feed using a neutral detergent. The neutral detergent extracts sugars, lipids, organic acids, pectin, N compounds (not including proteins), and water soluble proteins among others. These components that are extracted are very digestible in animals. The insoluble components are called neutral detergent fiber which contains cell wall material such as cellulose, hemicellulose, ligin, and some minor cell wall components as well. By using these Van Soest fractions neutral detergent fiber as an index of gut fill, voluntary intake of feed can be predicted.
Since average chemical composition of feedstuffs is so available, why go to all the trouble to test and analyze feedstuffs?
While average composition of feedstuff has been widely used as a guide to nutritive value of feed there is considerable variation that exists within each kind of feed. In many operations, analyses of feeds can aid in more accurate ration formulation for faster and/or more efficient gains.
Forages
is a plant material eaten by grazing livestock. Historically, the term forage has meant only plants eaten by the animals directly as pasture, crop residue, or immature cereal crops, but it is also used more loosely to include similar plants cut for fodder and carried to the animals, especially as hay or silage.
NFE
is the difference between original sample weight and the sum of weights of water, ether extract, crude protein, crude fiber, and ash -contains sugar, starches and may contain hemicellulose and lignin in forages
Ash
is the residue remaining after combustible material has burned off in furnace heated to 500C. If high values are seen contamination could be the cause
Crude protein
known as Kjedahl method where it is dependent on measurement of N in test material. Then multiply percent by 6.25
Ether extract
method for determining crude fat and is effective if the ether extract is made of primarily fats and fatty acid esters
