understanding your forage test results

EM 8801April 2002

$1.00

Understanding YourForage Test ResultsA. Ruddell, S. Filley, and M. Porath

Amy Ruddell, Extension agent, Coosand Curry counties; Shelby Filley,Extension agent, Douglas County; andMarni Porath, Extension agent, LakeCounty; Oregon State University.

Balanced nutrition is importantfor efficient livestock production.Daily nutrient requirementsvary depending on the phase ofproduction. Knowing the nutrientcomposition of feeds and matchingfeeds to animal requirements ata given stage of production willensure that nutritional needsare met. Forage analysis is amanagement tool that providesinformation needed for properlivestock nutrition.

Using the resultsOnce you have your forage test

results, carefully go through eachitem and consider how the resultswill influence the way you use thefeed in your livestock nutritionprogram. You can use the informa-tion to formulate a balanced rationfor your livestock or for generalfeeding decisions.

You need to understand thenutrient requirements for differentlivestock in order to match forageresources with animal needs.These requirements can be foundin publications such as NutrientRequirements of Domestic Animalsand the Cow–Calf ManagementGuide and Cattle Producer’sLibrary (see “References,”page 3).

This publication describescommon terms found in laboratoryforage analyses. A sample testresult sheet is included on page 4.The following information pertainsto ruminants, including beef anddairy cattle and sheep.

Moisture is the percent water ina sample.

As-fed is the actual feed,including moisture content, as it isoffered to the animal. Also referredto as as-sampled or as-received, ifnot altered between sampling,testing, and feeding time.

Dry matter (DM) is the feedwithout the moisture (DM = 100%– Moisture). It represents every-thing in the sample other thanwater, including protein, fiber, fat,minerals, etc.

On an as-fed basis, animalsmust consume more of a wet feedto receive the same amount of drymatter as they would from a drierfeed. For example, if an animalconsumes 25 lb of 90 percentDM hay, it consumes about 23 lbof dry matter (25 x 0.9). If haylageat 40 percent dry matter is substi-tuted for the above hay, the animalmust consume about 58 lb ofhaylage as-fed (23 ÷ 0.4) to receivethe same amount of dry matter.Thus, it is very important to knowthe dry matter content of a feed to

establish feeding rates and toensure that livestock receive theproper amount of feed to meettheir daily needs.

Dry matter basis meansnutrient results for the sample withthe water removed. Feeds vary intheir moisture content, as dis-cussed above. Nutrient content offeeds can be compared directly byremoving the water (DM basis).

For example, suppose you wantto compare the protein content ofhay (90 percent DM) andhaylage (40 percent DM). On anas-sampled basis, the hay tested10 percent protein and the haylage7 percent protein. The hay seemsto have a higher protein level.However, on a DM basis (withoutthe water), the hay is 11 percentprotein (10 ÷ 0.9), and the haylageis about 18 percent protein(7 ÷ 0.4). Thus, the haylage ishigher in protein per pound of drymatter. Animals will consumemore protein per pound of drymatter from the haylage than theywill from the hay.

Make sure the animal nutrientrequirements and lab results areexpressed on the same basis, eitherDM or as-fed. Always use theDM matter basis when comparingfeeds.

A more recent revision exists, For current version, see: https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/em8801.pdf

ProteinProteins are made up of amino

acids, known as the buildingblocks of the body. Protein isessential for tissue growth andrepair, maintenance, lactation,growth, and reproduction.

Crude protein (CP) is anestimate of the protein content ofthe feed. The normal range is 6 to20 percent on a DM basis. Labora-tories measure the nitrogen (N)content of forage and then calcu-late crude protein using the for-mula CP = %N x 6.25. The factorof 6.25 is used because protein isapproximately 16 percent nitrogen(100 ÷ 16 = 6.25).

Crude protein includes both trueprotein and nonprotein nitrogen.True proteins are organic com-pounds made up of amino acids.They are a major component ofvital organs, tissue, muscle, hair,skin, milk, and enzymes. Nonpro-tein nitrogen is urea and ammonia,which can be used by rumenmicrobes to make protein for theanimal. Nonprotein nitrogen is notused as efficiently as true proteinwhen animals consume low-quality forages.

Adjusted crude protein is thecrude protein with adjustments foravailability to the animal. Someprotein might be tied up with thefiber and unavailable to the animal.

CarbohydratesCarbohydrates make up the

structure of plants (stems, cellwalls) and the cell contents thatprovide energy.

Neutral detergent fiber (NDF)is a measure of hemicellulose,cellulose, and lignin, whichrepresent the fibrous bulk of

forage. These components arecalled cell wall or structuralcarbohydrates. They give the plantrigidity, enabling it to supportitself as it grows. Cellulose andhemicellulose can be partiallybroken down by microbes in therumen to provide energy to theanimal.

NDF is negatively correlatedwith intake; a high percent NDFreduces forage intake. A normalrange is 30 to 60 percent on a DMbasis.

Acid detergent fiber (ADF) isa measure of cellulose and lignin.ADF is negatively correlated withoverall digestibility; high ADFfeed is less digestible. A normalrange is 25 to 45 percent on aDM basis.

Relative feed value (RFV)ranks feed based on digestibility(ADF) and intake (NDF) potential.An RFV of 100 is considered theaverage score and represents analfalfa hay containing 41 percentADF and 53 percent NDF on a drymatter basis. The higher the RFV,the better the forage quality.

Use a range of RFV valueswhen classifying a forage. A goodguideline is to accept anythingwithin at least +/-5 points of thetarget value. For example, if anRFV of 150 is the target, anyforage testing 145 to 155 should beconsidered to have an equivalentvalue.

RFV is used in feed marketingand comparisons, not in balancinga ration for animals.

Nonstructural carbohydrates(NSC) are starches and sugarsinside the cell that serve as energysources for the animal. NSC iscalculated as follows: 100% –(CP% + NDF% + Fat% + Ash%).

FatCrude fat contains fat and other

compounds soluble in ether. Fatcontains 2.25 times the energyfound in carbohydrates andproteins. It is added to rations toboost energy concentration whenintake may be limiting.

EnergyEnergy is used in all biological

processes and is essential for life.For livestock, energy requirementsare determined for maintenance,growth or gain, lactation, repro-duction, and activity level. Failureto supply adequate energy resultsin poor performance. Energyvalues usually are not measureddirectly from feed but are pre-dicted using equations and rela-tionships with various nutrients.

Total digestible nutrients(TDN) is the sum of the digestibleprotein, digestible NSC, digestibleNDF, and 2.25 times the digestiblefat.

Net energy for maintenance(NEm) is an estimate of the energyvalue of a feed to maintain animaltissue without gain or loss ofweight. NE

m is used in formulating

beef and sheep rations for mainte-nance plus energy for pregnancyand lactation.

Net energy for lactation (NEl)is used in formulating rations fordairy cattle. It estimates the energyavailable from the feed to supportan animal’s requirements formaintenance plus milk productionduring lactation and for mainte-nance plus the final 2 months ofgestation for dry, pregnant cows.

Net energy for gain (NEg) isan estimate of the energy value ofa feed used for body weight gainabove that required for main-tenance. It is used in ration


balancing for beef and sheep whengain is desired.

MineralsMinerals make up 3 to 5 percent

of an animal’s body dry weight.They have multiple functionswithin the animal. They areclassified into two groups:macrominerals (major minerals),which normally are present atgreater levels in the animal body orneeded in relatively larger amountsin the diet, and microminerals(trace minerals), which are presentat lower levels or needed in verysmall amounts. Minerals cannot besynthesized; they must comefrom the diet (feed plus mineralsupplement).

Macrominerals andtheir functions

Calcium (Ca)—bone and teethformation, blood clotting, musclecontractions, milk component,transmission of nerve impulses,cardiac regulation, and enzymefunction

Phosphorus (P)—bone andteeth formation, key component ofenergy metabolism, milk compo-nent, body fluid buffer systems

Sodium (Na)—acid–basebalance, muscle contraction, nervetransmission, osmotic pressureregulation and water balance,glucose uptake, and amino acidtransport

Chloride (Cl)—acid–basebalance, osmotic pressure regula-tion and water balance, componentof gastric secretions

Magnesium (Mg)—enzymeactivator, found in skeletaltissue and bone, neuromusculartransmissions

Potassium (K)—osmoticpressure regulation and waterbalance, electrolyte balance,

acid–base balance, enzyme activa-tor, muscle contraction, nerveimpulse conductor

Sulfur (S)—used for microbialprotein synthesis, especially whennonprotein nitrogen is fed

Microminerals andtheir functions

Cobalt (Co)—required forvitamin B

12 synthesis

Copper (Cu)—required forhemoglobin synthesis, coenzymefunctions

Fluoride (F)—prevents toothdecay

Iodine (I)—required for properthyroid function and to guardagainst goiter, still births, andwoolless lambs

Iron (Fe)—hemoglobin andoxygen transport, enzyme systems

Manganese (Mn)—growth,bone formation, enzyme activa-tion, fertility

Molybdenum (Mo)—compo-nent of enzymes, may enhancerumen microbial activity

Selenium (Se)—antioxidantproperties, prevention of whitemuscle disease and retainedplacenta

Zinc (Zn)—enzyme activation,wound healing, skin health, someimpact on udder health (reducedsomatic cell counts)

Other itemspH measures the degree of

acidity. Good corn silage typicallyhas a pH of 3.5 to 4.5 and haycropsilages 3.8 to 5.3.

Nitrates can be accumulated byforage plants under stressedconditions such as drought,freezing, or heavy fertilization.Corn, sorghum, sudangrass, andoat hay are nitrogen accumulatorseven without added stress to theplants.

Forage with nitrate nitrogenlevels of less than 1,000 ppm aresafe to feed. Those with nitratenitrogen levels of greater than4,000 ppm may be toxic; do notfeed. Use forages with levelsbetween 1,000 and 4,000 ppm withextreme caution, and restrict whichanimals receive them. Immatureruminants are more susceptiblethan more mature animals. How-ever, pregnant ruminants may notbe as tolerant of higher levels asnonpregnant animals. This couldbe because signs of subacutenitrate toxicity are abortion andother reproductive problems.

Acid detergent insolublenitrogen (ADIN or ADF-N) is ameasure of the protein bound tofiber due to overheating of storedforage. This protein, which isindigestible, is called “heatdamaged.”

ReferencesNutrient Requirements of Domestic

Animals (National ResearchCouncil, National AcademyPress, Washington, DC).http://www.nap.edu

Cow–Calf Management Guideand Cattle Producer’s Library(University of Idaho Coopera-tive Extension System,Moscow, ID).

OSU Extension publications You can access our Publica-

tions and Videos catalog and manyof our publications through ourWeb page (http://eesc.orst.edu).

AcknowledgmentsThis publication was modeled

after a publication by Dairy One,DHIA, Ithaca, NY, Understandingand Significance of ForageAnalysis Results, by Paul Sirois.


http://extension.oregonstate.edu/catalog/index.php

© 2002 Oregon State University. This publication may be photocopied or reprinted in its entirety for noncommercial purposes.Produced and distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Extension work is a cooperative program of Oregon StateUniversity, the U.S. Department of Agriculture, and Oregon counties. Oregon State University Extension Service offers educational programs, activities,and materials—without regard to race, color, religion, sex, sexual orientation, national origin, age, marital status, disability, and disabled veteran orVietnam-era veteran status. Oregon State University Extension Service is an Equal Opportunity Employer.

Published April 2002.

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