understanding forage quality · adequate animal nutrition is essential for high rates of gain,ample...
TRANSCRIPT
Understanding forage qualityDon Ball
Mike Collins
Garry Lacefield
Neal Martin
David Mertens
Ken Olson
Dan Putnam
Dan Undersander
Mike Wolf
Suggested retail price $3.50
ContentsUnderstanding forage quality 1
What is forage quality? 2
Factors affecting forage quality 3
Species differences 3
Temperature 3
Maturity stage 4
Leaf-to-stem ratio 4
Grass-legume mixtures 5
Fertilization 5
Daily fluctuations in forage quality 5
Variety effects 5
Harvesting and storage effects 6
Sensory evaluation of hay 7
Laboratory analysis of forage 8
Laboratory analytical techniques 8
Laboratory proficiency 10
Understanding laboratory reports 11
Matching forage quality to animal needs 12
Reproduction 12
Growth 13
Fattening 13
Lactation 13
Economic impacts of forage quality 14
Pasture forage quality 14
Hay quality 15
Other considerations 15
Key concepts to remember 15
Additional information 15
Glossary 16
Understanding forage quality
Forage quality is defined in variousways but is often poorly under-stood. It represents a simple
concept, yet encompasses much com-plexity. Though important, foragequality often receives far less consid-eration than it deserves.
Adequate animal nutrition is essentialfor high rates of gain, ample milk pro-duction, efficient reproduction, andadequate profits (see sidebar).However, forage quality varies greatlyamong and within forage crops, andnutritional needs vary among andwithin animal species and classes.Producing suitable quality forage for agiven situation requires knowing thefactors that affect forage quality, thenexercising management accordingly.Analyzing forages for nutrient contentcan be used to determine whetherquality is adequate and to guideproper ration supplementation.
In recent years, advances in plant andanimal breeding, introduction of newproducts, and development of newmanagement approaches have madeit possible to increase animal perform-ance. However, for this to be realized,there must be additional focus onforage quality. The purpose of thispublication is to provide informationabout forage quality and foragetesting that can be used to increaseanimal performance and producerprofits.
IMPORTANCE OF FORAGE QUALITYForage quality has a direct effect on animal performance, forage value, and, ultimately, on profits. The followinggraphs show the links between quality, performance, and returns.
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0.0 0.5 1.0 1.5 2.0 2.5
endophyte-infected tall fescue
Weight gainStocker beef cattle gains from different forages, Alabama
average daily gain (lb)
hybrid sorghum-sudangrass
sericealespedeza
orchardgrass& white clover
alfalfa
annualryegrass
milk
pro
du
ctio
n (l
b/a
cre)
low-quality hay
high-quality hay
increase = $400 profit
0
3,000
6,000
9,000
12,000
15,000
Milk productionProduction from 8 tons/acre of alfalfahay of either low- or high-quality, Wisconsin
Reproductive efficiencyConception rates of cows grazing fescueor fescue/clover, Indiana & Illinois
con
cep
tio
n r
ate
(%)
tall fescue
Indiana Illinois
clover & tall fescue0
20
40
60
80
100
Hay sale pricesPrices paid in quality-tested hay auctions, Wisconsin, 1984-98
pri
ce p
aid
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on
)
>150<75 125-15075-86 87-102 103-124
forage quality (RFV)
160
140
120
100
80
60
40
20
0
Effect of forage quality on hay priceaverage all California markets (1996-2000)
supreme (<27% ADF)premium (27-30% ADF)good (30-32% ADF)fair (32-35% ADF) av
erag
e p
rice
pai
d ($
/to
n)
1 52 3 4year
$160
$140
$120
$100
$80
$60
$40
$20
$0
What is foragequality?
Forage quality can be defined as theextent to which a forage has thepotential to produce a desired
animal response. Factors that influenceforage quality include the following.
■ Palatability Will the animals eatthe forage? Animals select oneforage over another based onsmell, feel, and taste. Palatabilitymay therefore be influenced bytexture, leafiness, fertilization, dungor urine patches, moisture content,pest infestation, or compoundsthat cause a forage to taste sweet,sour, or salty. High-quality foragesare generally highly palatable.
■ Intake How much will they eat?Animals must consume adequatequantities of forage to performwell. Typically, the higher thepalatability and forage quality, thehigher the intake.
■ Digestibility How much of theforage will be digested? Digestibility(the extent to which forage isabsorbed as it passes through ananimal’s digestive tract) variesgreatly. Immature, leafy planttissues may be 80 to 90% digested,while less than 50% of mature,stemmy material is digested.
■ Nutrient content Once digested,will the forage provide an adequatelevel of nutrients? Living forageplants usually contain 70 to 90%water. To standardize
analyses, forage yield and nutrientcontent are usually expressed on adry matter (DM) basis. Forage drymatter can be divided into twomain categories: (1) cell contents(the non-structural parts of theplant tissue such as protein, sugar,and starch); and (2) structural com-ponents of the cell wall (cellulose,hemicellulose, and lignin).
■ Anti-quality factors Various com-pounds may be present in foragethat can lower animal perform-ance, cause sickness, or even resultin death. Such compounds includetannins, nitrates, alkaloids, cyano-glycosides, estrogens, and myco-toxins. The presence and/orseverity of these elements dependon the plant species present(including weeds), time of year,environmental conditions, and
animal sensitivity. High-qualityforages must not contain harmfullevels of anti-quality components.
■ Animal performance is theultimate test of forage quality,especially when forages are fedalone and free choice. Foragequality encompasses “nutritivevalue” (the potential for supplyingnutrients, i.e., digestibility andnutrient content), how muchanimals will consume, and anyanti-quality factors present. Animalperformance can be influenced byany of several factors associatedwith either the plants or theanimals (figure 1). Failure to giveproper consideration to any ofthese factors may reduce ananimal’s performance level, whichin turn reduces potential income.
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U N D E R S T A N D I N G F O R A G E Q U A L I T Y
Animal performanceNutrients utilized per unit of time
(true feeding value)
Plant/animal complex■ Balance of nutrients relative to need
■ Extent of digestion of nutrients
■ Rate of digestion of nutrients
■ Effective utilization of digested nutrients
■ Availability and palatability of forage
■ Level of intake
■ Response to anti-quality factors
■ Interaction with supplements
Potential animalperformance
Physiologicalfactors
Geneticfactors
Environmentalfactors
GenotypeBody size
Sex
AgeBody condition
Health
ClimatePests
Herd effects
GenotypePlant partMaturation
ClimateSoilPests
Potential foragefeeding value
Potential nutritive value
Anti-qualityfactors
Potential intake
Figure 1. Factors that affect animal performance on forage.
Source: Marten, G.C., D.R. Buxton, and R.F. Barnes, 1988. Feeding value (foragequality). In Alfalfa and Alfalfa Improvement, Monograph no. 29. Madison, Wis.:ASSA/CSSA/SSSA.
Factors affectingforage quality
Many factors influence foragequality. The most important areforage species, stage of maturity
at harvest, and (for stored forages)harvesting and storage methods.Secondary factors include soil fertilityand fertilization, temperatures duringforage growth, and variety.
Species differencesLegumes vs. grasses Legumes generally produce higherquality forage than grasses. This isbecause legumes usually have lessfiber and favor higher intake thangrasses. One of the most significantbenefits of growing legumes withgrasses is improvement of foragequality.
A comparison of timothy and alfalfafrom the second cut of a mixed stand(figure 2) illustrates typical species dif-ferences in quality. Alfalfa, at earlybloom, had 16% crude protein (CP)compared with 9.5% in timothy.However, applying substantial amountsof nitrogen fertilizer to grasses canmake their CP levels comparable tolegume forage.
In the same comparison, timothy hadconsiderably higher levels of neutraldetergent fiber (NDF) than alfalfa.Typically, higher NDF (total fiber) levelsand a slower rate of fiber (cell wall)digestion for grass forages results inlower voluntary intake compared withlegumes. Faster digestion allows moreforage (and thus more nutrients) to beconsumed.
Cool-season vs.warm-season grassesThere is considerable variation inforage quality among the grassesused as cultivated forages in theUnited States. Forage grasses aredivided into two broad categories:cool season (adapted to temperateregions) and warm season (bestadapted to tropical or subtropicalenvironments). Cool-season grassesinclude orchardgrass, Kentucky blue-grass, perennial and annual ryegrass,and tall fescue. Bermudagrass, bahia-grass, dallisgrass, and corn areexamples of warm-season grasses.
Cool-season species are generallyhigher in quality than warm-seasongrasses. The digestibility of cool-season grass species averages about9% higher than warm-season grasses.Minimum crude protein levels foundin warm-season grasses are also lowerthan those found in cool-seasongrasses. Within each category, annualgrasses are often higher in qualitythan perennials. Due to differences inleaf anatomy (tissue arrangement orstructure), warm-season grassesconvert sunlight into forage more effi-ciently than cool-season grasses, buttheir leaves contain a higher propor-tion of highly lignified, less digestibletissues.
TemperaturePlants grown at high temperaturesgenerally produce lower qualityforage than plants grown undercooler temperatures, and cool-seasonspecies grow most during the coolermonths of the year. However, forage ofany species tends to be lower inquality if produced in a warm regionrather than a cool region. For example,in one study annual ryegrass grown attemperatures of 50° to 59°F producedforage made up of 59% leaf material,but only 36% leaf matter when grownat 68° to 77°F.
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fora
ge
qu
alit
y fa
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)
crude protein
NDF ADF cell walldigestibility
cell walldigestionrate/hour
0
10
20
30
40
50
60
70
alfalfatimothy
Source: Collins, M. 1988. Composition and fibre digestion in morphologicalcomponents of an alfalfa–timothy sward. Anim. Feed Sci. Tech. 19:135–143.
Figure 2. Forage quality of alfalfa and timothy components of a mixture.
Maturity stageMaturity stage at harvest is the mostimportant factor determining foragequality of a given species (table 1 andfigure 3). Forage quality declines withadvancing maturity. For example, cool-season grasses often have dry matter(DM) digestibilities above 80% duringthe first 2 to 3 weeks after growth ini-tiation in spring. Thereafter, digestibil-ity declines by 1⁄3 to 1⁄2 percentageunits per day until it reaches a levelbelow 50%.
Maturity at harvest also influencesforage consumption by animals. Asplants mature and become morefibrous, forage intake drops dramati-cally.Typical DM digestibility and intakevalues for cool-season grass hays har-vested at different stages of maturityare shown in table 1. Numerous studieshave shown similar effects in many dif-ferent species.
Intake potential decreases and NDFconcentration increases as plants age.This is because NDF is more difficult todigest than the non-fiber componentsof forage. Also, the rate at which fiberis digested slows as plants mature.Therefore, digestion slows dramati-cally as forage becomes more mature.
Leaf-to-stem ratioReduced leaf-to-stem ratio is a majorcause of the decline in forage qualitywith maturity, and also the loss inquality that occurs under adverse haycuring conditions. Leaves are higher inquality than stems, and the proportionof leaves in forage declines as theplant matures.
The variation in quality of leaves andstems is illustrated in table 2. Theoldest portion of alfalfa stems had lessthan 10% CP compared with 24% inalfalfa leaves. Stems of both specieshad much higher fiber levels thanleaves, but the older, lower alfalfaleaves were similar in quality to theupper, younger leaves. However, olderalfalfa stem tissue was considerablylower in quality than young stemtissue.
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U N D E R S T A N D I N G F O R A G E Q U A L I T Y
rela
tive
qu
alit
y
growth stage
crude protein
leaves
minerals
high
medium
leafyleafy
bootprebud
headingbud
bloombloom
grasseslegumes
low
fiberstems
Figure 3. Effect of plant maturity on forage intake and digestibility.
Source: Adapted from Blaser, R., R.C. Hammes, Jr., J.P. Fontenot, H.T. Bryant, C.E. Polan,D.D. Wolf, F.S. McClaugherty, R.G. Klein, and J.S. Moore. 1986. Forage–animal management systems. Virginia Polytechnic Institute, Bulletin 86-7.
Table 1. Effect of plant maturity on intake and digestibility of cool-season grass hays by lactating cows (summary of several studiesinvolving various grasses).
relativecutting growth hay intake hay digestibledate stage per day digestibility DM intake
% body weight/day ———— % ————June 3–4 vegetative 2.64 63.1 166June 11–12 early boot 2.36 65.7 154June 14–15 late boot 2.45 62.6 153June 16–18 early head 2.28 58.5 133July 1 bloom 2.30 52.7 121July 5 bloom 2.13 52.2 111July 7–8 bloom 2.05 52.2 107July 9–10 late bloom 1.95 51.5 100
Source: Stone, J.B., G.W. Trimberger, C.R. Henderson, J.T. Reid, K.L. Turk, and J.K. Loosli. 1960.Forage intake and efficiency of feed utilization in dairy cattle. J. Dairy Sci. 43:1275–1281.
Table 2. Leaf and stem quality of alfalfa and timothy components ofa mixture.
plant % of thecomponent whole plant CP NDF ADF
Alfalfa ——————————— % ———————————upper leafa 30.7 23.9 27.7 18.5lower leaf 12.8 21.8 25.9 16.6upper stema 6.5 13.4 52.6 38.6lower stem 50.0 9.6 67.8 52.9
Timothyleaf 29.6 18.3 49.1 25.5stem 70.4 5.8 72.5 42.6
aUpper leaf and stem were taken from the last five internodes on each stem.Source: Collins, M. 1988. Composition and fibre digestion in morphological
components of an alfalfa-timothy sward. Anim. Feed Sci. Tech. 19:135–143.
Reproductive growth lowersleaf-to-stem ratio, and thus foragequality. Most cool-season grassesrequire a period of cool temperatures(vernalization) for flowering, so theyproduce reproductive stems only inthe spring. Thus, the forage quality ofregrowth of these grasses is greaterand changes less over time becausethey have higher leaf-to-stem ratiosthan first-growth forage. Legumes andsome grasses such as bermudagrasscan flower several times each season,so their forage quality patterns areless closely linked to season.
Grass–legume mixturesGrass–legume mixtures generally havehigher crude protein concentrationand lower fiber concentration thanpure grass stands. In Georgia, mixturesof seven legumes with bermudagrass(receiving no nitrogen fertilizer) rangedfrom 11 to 13% CP compared with only11% CP in pure bermudagrass receiv-ing 90 pounds/acre of nitrogenannually. In another study, first-cuttingalfalfa containingabout 30%timothy had a CPlevel of 17.5%compared with20.5% in alfalfawith no grass.
FertilizationFertilization of grasses with nitrogen(N) often substantially increases yieldand also generally increases CP levelsin the forage. In one study, fertilizingswitchgrass with 70 pounds/acre ofnitrogen raised CP from 5.3 to 6.4%,and increased voluntary intake by11%. (Fertilizing alfalfa and otherlegumes with nitrogen to improvequality is not recommended.)Fertilization usually has little or noeffect on digestibility. Fertilizationwith phosphorus (P), potassium (K), orother nutrients that increase yield mayactually slightly reduce forage qualitywhen growth is rapid. Excessive levelsof some elements such as potassiummay in some cases decrease the avail-ability of other elements such as mag-nesium (Mg) in the diet.
Daily fluctuations inforage qualityAs early as the 1940s, changes insoluble carbohydrate levels in alfalfawere linked to time of day. Plants accu-mulate soluble carbohydrates duringdaylight and then use them overnight.Thus, soluble sugars are lowest in themorning and highest after a day ofbright sunshine. Recent studies in lowrainfall climates have shown higherforage quality when alfalfa is harvestedin the late afternoon rather than in themorning. It appears that the advantageof afternoon harvest is greatest oncool, sunny days and when the forageis highly conditioned to increase dryingrates and minimize respiration in thewindrow. However, afternoon harvestsmay not be advisable in high rainfallareas where every hour of good dryingtime is needed in curing hay.
Variety effectsThere are many examples of plantbreeding improving forage quality.The variety ‘Coastcross-1’ bermuda-grass is about 12% higher indigestibility than ‘Coastal’ bermuda-grass, supporting 30% higher averagedaily gains by beef steers. In speciessuch as timothy that have a widerange of maturity dates, later-maturing varieties tend to be slightlylower in digestibility because earlytypes make more of their growthunder lower temperatures. Somesilage corn varieties have higher graincontent and/or stover digestibilitythan others.
The development of multifoliatealfalfa varieties (having more thanthree leaflets per leaf ) is a strategyaimed at increasing forage quality, butsome multifoliate varieties have nohigher leaf percentage than tradi-tional trifoliate varieties. Some trifoli-ate varieties exhibit superior quality,but care should be taken to assurethat a “high-quality” variety is not sub-stantially lower in yield.
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Harvesting and storage effectsLeaf shatter, plant respiration, andleaching by rainfall during field dryingof hay can significantly reduce foragequality, particularly with legumes.Figure 4 illustrates typical effects ofrainfall during the drying process.Moderate rain damage reduced alfalfaCP levels slightly and digestibility dra-matically, but NDF and ADF levelsincreased sharply. Red clover hayquality was also greatly reduced byrain, even though crude proteinincreased. The total amount of crudeprotein did not increase; the percent-age of crude protein in the remainingdry matter was higher due to leachingof highly soluble constituents.However, leaching also increases theporportion of unavailable ADIN (seeglossary) in the hay.
Rainfall during curing damageslegume leaves most. For alfalfa hayexposed to both drying and leachinglosses, more than 60% of the totallosses of dry matter, CP, ash, anddigestible DM were associated withthe leaves. Rain during field drying hasless impact on the forage quality ofgrasses than legumes. In one study,alfalfa hay that received rain was 12percentage units less digestible thanfresh forage, compared with a differ-ence of only 6 percentage units forgrass hay produced under similar con-ditions. Damage from rain increases asforage becomes dryer, and is espe-cially severe when rain occurs after itis ready to bale.
Quality losses also occur due toweathering, plant respiration, andmicrobial activity during storage. Inhigh rainfall areas, losses can be largefor round bales stored outside, due toweathering of the outer layers. In anIndiana study, digestibility and crudeprotein content of the unweatheredcenter portions of round bales ofmixed grass hay stored outside for 5months was 59% and 13.5%, respec-tively, while the weathered outerportions of bales had a digestibility of43%, and a crude protein content of16.4%. In the same study, thedigestibility and crude protein contentof unweathered centers of alfalfa/grass bales were 57% and 14.3%,respectively, and 34% and 16.9% forthe weathered outer portions of bales,respectively.
In a study in Louisiana (figure 5), baledryegrass stored outdoors on theground lost 40% of the initial DMduring 1 year of storage. Protectedbales lost an average of 10% of theinitial DM during the same period.Refusal during feeding to mature cowsranged from only 1% for inside-storedbales to 22% for bales stored outsideon the ground.
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U N D E R S T A N D I N G F O R A G E Q U A L I T Y
loss
(%)
dry matter loss feed refusal*0
5
10
15
20
25
30
35
40on ground, no coverrack with coverinside
Figure 5. Changes during storage of ryegrass round bales in Louisiana.
*Refusal measurements were made after 7 months ofstorage.
Source: Verma, L., and B.D. Nelson. 1983. Changes inround bales during storage. Trans. ASAE. 26:328-332.
fora
ge
qu
alit
y fa
cto
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)
crude protein
NDF ADF digestibility crude protein
NDF ADF digestibility0
10
20
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40
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70
80
0
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50
60
70
80
Alfalfa Red clover
no rain1.6 inches rain2.4 inches rain
no rain1.6 inches rain2.4 inches rain
Source: Collins, M. 1983. Wetting and maturity effects on the yield and quality of legume hay.Agron. J. 75:523-527.
Figure 4. Change in forage quality of alfalfa and red clover hays exposed torain during curing.
Some storage and feeding losses areinevitable. Estimated losses from har-vested forage stored at variousmoisture contents are provided infigure 6.
Sensory evaluation of hay
Much can be learned from acareful sensory examination ofhay. First, the plant species
present can be determined. Does thehay consist almost exclusively of a par-ticular forage crop? Does the foragecrop tend to be higher in quality thanother forages? Does the hay containweeds? If so, what percentage isweeds and how much nutritionalbenefit do they provide to livestock?Could they be toxic?
The maturity of the hay, one of themain factors determining foragequality, can be visually assessed. Thenumber and maturity of seed headsand blooms, and the stiffness andfibrousness of the stems are indicatorsof plant maturity.
Leafiness is particularly important;the higher the leaf content, the higherthe forage quality. Leafiness can beaffected by plant species, by stage ofmaturity at harvest, and (especially inlegume hays) by handling that resultsin leaf loss.
Texture is a consideration. Softnessusually results from early cutting, highleaf content, and a suitable moisturelevel at baling. When hay is “very soft”and pliable, it is difficult to distinguishbetween stems and leaves just byfeeling the hay.“Soft” hay is soft to thetouch, but stems can be detectedeasily.“Slightly harsh” hay has stemsthat are a little rough.“Harsh or brittle”hay is dry, stemmy, and unpleasant tothe touch.“Extremely harsh” hay caninjure an animal’s mouth, loweringintake.
Color helps sell hay to the averagebuyer. Color alone is not a good indi-cator of forage quality, but it can be anindicator of harvest and storage con-ditions. A bright green color suggeststhat hay was cured quickly and pro-tected during storage. Slow curingprolongs plant respiration, whichreduces forage quality. Hay that is raindamaged after being partially driedwill lose color due to leaching. Moldgrowth on leaves and stems orexposure to sunlight will also bleachhay. Baling at moisture contents at orabove 20 to 25% may cause high baletemperatures that result in tan tobrown or black colors (commonlycalled “tobacco hay”).
A pleasant odor indicates hay wascured properly. Moldy, musty odorsmay occur in hay stored at moisturecontents above 16 to 18% (above 14%for 1-ton square bales). Animals mayrespond to off-odors by going offfeed. Odors caused by heating(>125°F) result from hay being baledat too high a moisture content or fromensiling forage that is too dry.Interestingly, hay with a slightlycaramelized odor is often quite palat-able to livestock, even though thequality is reduced. (The odor of silagecan indicate good or bad fermenta-tion; if it smells of butyric acid—similar to rancid butter—it may lackpalatability, and low animal intake islikely.)
Dusty hay is usually the result of soilbeing thrown into the hay by raketeeth hitting the soil. The presence orabsence of molds, dust, and odor arereferred to as organoleptic qualities.
Visual inspection can also detectforeign matter (anything that has littleor no feed value).Tools, sticks, rocks,wire, items of clothing, dead animals,and cow chips have all been found inhay and are obviously undesirable.Dead animals in hay can causebotulism, a deadly disease that can killfarm animals.
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direct-cutsilage
wiltedsilage
barn-driedhay
haylage
moisture range for concrete tower silos
field-curedhay
dry
mat
ter
loss
(%)
moisture at harvest (%)
0
10
20
30
40
50storage loss
harvest loss
80 70 60 50 40 30 20 10
Figure 6. Estimated dry matter loss during harvest and storageof hay-crop forages ar various moisture levels.
Source: Michigan State University
Laboratoryanalysis of forage
Though sensory evaluation is ofvalue, accurate laboratory testing offeed and forage is required to
provide the information needed to for-mulate animal rations. Testing to assessquality also provides a basis for com-mercial hay sales.
A forage analysis should reflect theaverage quality of the material beingtested. Only a few grams of materialrepresents tons of forage, so it isessential to obtain a representativesample. Therefore, sampling techniqueis extremely important (see sidebarson how to properly sample hay, silage,and pasture forage).
Laboratory analytical techniquesLaboratory analyses are used to deter-mine the nutritive value of forages. Atypical forage analysis includes meas-urements of dry matter, crude protein,and fiber (acid detergent fiber andneutral detergent fiber). Sometimesash is measured, and when heat-damaged protein is suspected, aciddetergent insoluble crude proteinshould be measured. Many otherresults provided on laboratory reports(digestible energy or protein, netenergy, total digestible nutrients,potential intake, etc.) are calculated or
estimated from measured analyses.See figure 10 on page 17.
Dry matter—Dry matter (DM) is theportion (weight) of forage other thanwater. Nutrients and other feed charac-teristics are typically reported on a DMbasis to eliminate the dilution effect ofmoisture and to allow more directcomparison of feeds and easier formu-lation of diets. Dry matter percentagesshould be used to adjust as-receivedtonnages to determine true yields offorage and to determine the actualamount of forage (without the water)being bought or sold. To compareprices and nutritive value among lotsof forage they should be adjusted to aDM basis. Sometimes hay is comparedor sold on a 90% DM basis, whichclosely resembles the average DM ofair dried feeds.
For hay, excessively lowmoisture (less than 10%) couldindicate brittleness (and thuslow palatability) or excessiveleaf loss (linked with loweredforage quality), while highmoisture (greater than 14 to18%) indicates a risk of mold.For silage, excessively lowmoisture (below 45%) canindicate heat damage, whilehigh moisture (above 70%) canindicate poor fermentationand potential intake problems.
Detergent fiber analysis—Aciddetergent fiber (ADF) and neutraldetergent fiber (NDF) are frequentlyused as standard forage testing tech-niques for fiber analysis. Foragesamples are boiled in either a deter-gent solution (for NDF) or with addedacid (for ADF) according to definedprotocols. The residue is the NDF orADF fraction. NDF approximates thetotal cell wall constituents includinghemicellulose, whereas ADF primarilyrepresents cellulose, lignin, and ash.ADF is often used to calculatedigestibility, and NDF is used topredict intake potential. As fiberincreases, forage quality declines.
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HOW TO PROPERLY SAMPLE HAY Use a good probe—The hay probeshould have an internal diameter of3⁄8 to 5⁄8 inch. The cutting edgeshould be at right angles to the shaft,and kept sharp. Dull probes will notobtain a representative sample. Coresamplers that cut through a cross-section of a bale provide the best rep-resentation of stems and leaves. Avoidusing open augers as they selectivelysample leaves.
Sample at random—It is importantto select bales at random fromthroughout the hay “lot” (defined insidebar on page 10). Avoiding somebales and choosing others based onappearance will bias the sample. Forstacked hay, samples should be takenfrom bales at various heights in thestack.
Take enough core subsamples—Taking at least 20 core samples from ahay lot minimizes sample variation.
Use the proper technique—For rec-tangular bales of all sizes, insert thehay probe 12 to 18 inches deep at aright angle into the center of the endsof bales. For round bales, the probeshould be inserted at right angles tothe outside circumference of thebales.
Handle samples correctly—Combinecore samples from a given lot into asingle sample and store in a sealedplastic freezer bag. Samples should beprotected from heat or direct sun, andpromptly sent to a laboratory foranalysis. The sample should weighapproximately 1⁄2 to 3⁄4 pound. Withlarger samples, many labs will notgrind the entire sample. Too small asample will not adequately representthe hay lot.
Split samples correctly—To test theperformance of a particular laboratory(or the sampling technique), a fullyground and thoroughly mixed sampleshould be split and submitted.Unground samples should not be split.
U N D E R S T A N D I N G F O R A G E Q U A L I T Y
Protein—Protein is a key nutrient thatmust be considered both in amountand type for various animal diets. It iscommonly measured as crude protein(CP), which is 6.25 times the nitrogencontent of forage. Crude protein is usedbecause rumen microbes can convertnon-protein nitrogen to microbialprotein, which can then be used by theanimal. However, this value should beused with some care, as it is not appli-cable to non-ruminants or when highlevels of nitrate are present in theforage.
High-performing animals, especiallymilking dairy cows, need largeramounts of protein to be absorbedfrom the intestines than rumenmicrobes produce.Therefore, they needa certain amount of bypass protein (orRUP) in the ration. Recently, calibrationshave been developed that allow RUP inforages to be estimated using nearinfrared reflectance spectroscopy.
Acid detergent insoluble nitrogen(ADIN)—This estimates the nitrogenthat has low digestibility in the rumenand the intestine. It is important fordetermining the value of heat-damaged hay and silage. A little ADINis good because it increases bypassprotein, but too much may reducetotal protein availability.
Digestible energy estimates—Energy values are estimates of feedingtrial results. The vast majority are cal-culated, not measured, values. Thereare four basic approaches:
A. The most common has been tomeasure a single fiber fraction(usually acid detergent fiber) anduse it to predict digestibility, totaldigestible nutrients (TDN) or netenergy for lactation (NEl).
B. Summative equations are predic-tions of TDN or NEl from multiplemeasures of forage composition.These measures often includeneutral detergent fiber (NDF), NDFnitrogen, crude protein, etherextract, lignin, and acid detergent
HOW TO PROPERLY SAMPLE SILAGESampling during harvesting Collect three to five handfuls of chopped forage from the middle of a loadduring unloading, place in a plastic bag, and refrigerate immediately. Followthe same procedure for several loads throughout the day. Combine samplesfrom a single harvested field and mix well. Place the entire sample in a cleanplastic bag or other container, and seal tightly. Label each container with yourname and address as well as the date, sample number, and forage type. Storethe sample in a cool place (do not freeze) until you send it to a laboratory foranalysis. Repeat for each field, variety, or hybrid. If filling tower silos or silotubes, keep a record of where each lot is in the silo or tube. Feeding coloredplastic strips through the blower at the end of each lot may help identify thelots later.
Silos with seepage should be resampled upon feeding because loss ofsoluble compounds due to seepage will increase dry matter, acid detergentfiber and neutral detergent fiber, and decrease crude protein. Similarly,resample silos at feeding that were filled with forage at less than 50%moisture that may have heated excessively, causing increased acid detergentfiber and acid detergent fiber insoluble nitrogen. Recheck dry matter ofsilages at feed out. Fiber and protein are not likely to change much duringstorage, except as mentioned above, but moisture can change significantly.
Ensiled material from a tower siloDo not sample the spoiled material on the top or bottom of the silo; waituntil 2 to 3 feet of silage have been removed. Collect a 1 to 2 pound samplefrom the silo unloader while it is operating. Collect samples from oppositesides of the silo. Combine the samples and mix well. Place the entire samplein a plastic bag and handle as discussed above.
Ensiled material from a bunker siloIf feeding with a TMR (total mixed ration) mixer—Load silage from bunkerinto TMR mixer and mix well. Take several grab samples to collect a 1 to 2pound total sample. Place in a plastic bag and handle as discussed above.
If not feeding with a TMR mixer—Collect a 1 to 2 pound total sample fromthe different vertical layers of the silo face. Grab several handfuls from freshlyexposed forage after the day’s feeding has been removed. Do not sample thespoiled material on top of the silo. Combine handfuls and mix well. Place theentire sample in a clean plastic bag or other container, and seal tightly. Storeimmediately in a cold place until shipping. Label each container as indicatedearlier. Place in a plastic bag and handle as discussed above.
9
fiber nitrogen. These predictionscan be much more accurate thanthose of single fiber fractions, butare much more time consumingand expensive. Beware of laborato-ries that output “summative equa-tions” but don’t measure all com-ponents.
C. In vitro and in situ digestibility aregenerally considered the bestanalyses to use to predict animalperformance. Both use rumen fluidto digest the samples either in abeaker or test tube (in vitro) or in aporous bag placed in the rumenvia a fistula or port in the animal’sside (in situ).
D. Some scientists have begunlooking for additional factors tobetter describe the energy contentof forage. The most common addi-tional measure at present is todetermine nonfibrous carbohy-drate (NFC) or starch content. Thisis an especially good approach touse with high NDF or high starchfeeds. (See “NFC” in the glossary.)
Intake estimates—Voluntary intake, aprime consideration in feeding, isoften estimated based on neutraldetergent fiber (NDF) content. NDFconsists of the slowly digested andnondigestible fibrous portion of theplant (mostly hemicellulose, cellulose,lignin, and ash) which is most of thecell wall material (figure 7). As the NDFlevel increases, voluntary feed intaketends to decline. However, if NDF ofthe ration is too low, health problemssuch as acidosis, displaced aboma-sums, and foundering may occur.
Laboratory proficiencyThe accuracy of forage analysisdepends on the analytical proceduresused and the precision of laboratorytechniques.The National Forage TestingAssociation (NFTA) certifies the profi-ciency of laboratories with regard toaccurately testing hay and corn silagefor DM, CP, ADF, and NDF. It is advisableto use a NFTA certified laboratory. Fora current listing of certified laborato-ries, as well as more information aboutproficiency testing, visit NFTA’s website (www.foragetesting.org).
When evaluating a forage test report,keep in mind that none of the values,either measured or calculated, shouldbe considered absolute. There is vari-ability in hay stacks or silage, andsome variation associated with labanalysis. Normal lab variation, notincluding errors associated with poorsampling of forages, are considered tobe: CP (+/-0.5), NDF (+/-0.9), and ADF(+/-0.7). For example, a reported valueof 20% CP should be considered to beanywhere between 19.5 and 20.5%under normal circumstances. Relativefeed value (see glossary) will varywithin 8 points.
10
U N D E R S T A N D I N G F O R A G E Q U A L I T Y
Whole plant Whole plant analysis
leaves: 18-28% NDF12-20% ADF 22-35% CP
stems: 35-70% NDF 30-55% ADF 10-20% CP
cell contents (NSC)100% digestible
cell wall (NDF)20-60% digestible
Plantcell
25-35%
30-50%
15-25%
8-13%2-3%
Non-structuralcarbohydrates (NSC) (sugars & starch)
Structuralcarbohydrates (NDF: cellulose, hemicellulose,& lignin;ADF: cellulose & lignin) Proteins(soluble & bound)
Oils (lipids)Ash (minerals)
Figure 7. Structural components of alfalfa.
Adapted from: Putnam, Dan, 2000. Producing high quality alfalfa: Factors that influencealfalfa forage quality. Proc. CA Plant and Soil Conference, Jan. 19-20. Stockton, CA.
IDENTIFICATION OF A FORAGE LOTA lot is defined as forage takenfrom the same farm, field, and cutunder uniform conditions within a48-hour time period. A lot can rep-resent several truck or wagonloads, but all the forage shouldhave been harvested and storedunder identical conditions. Foraccurate test results, hay or silageshould be stored by lots, andseparate samples taken from eachlot. Any special conditions thatresult in quality differences in a lot,such as rain damage during harvestor excessive weed populations,should be noted to allow laterassessment of the reasons forquality variations.
11
Feed analysis report
ABC Feed Analysis Laboratory
Anywhere Street
Any City, ST 00000
Phone: 000-000-0000 Fax: 000-000-0000
Email: [email protected] Web: www.ABC.com
Client name:Joe Client
Feed identification: A-1-720
Address:123 Anystreet
Feed type:Alfalfa
City, State, ZipAnytown, AS 12345 Grower or feed origin: Doe farm
Phone:123-456-7890
Field location:South 720
Email:[email protected] Cutting and harvest date: First, 05/25/01
Feed preservation: Wilted for silage
Date sample analyzed: 05/29/01Sampler:
John Doe
Date results reported: 05/31/01Date sample taken: 05/25/01
Lab identification code: 00-000123Date sample shipped: 05/26/01
Invoice/accession code: 4567Date sample received: 05/28/01
Sample method and handling: Grab samples of chopped material from 12 loads.
Sample condition as received: Chopped material of adequate amount in good condition.
Nutrients, unitsMethod
As received 100% DM 90% DM
Analytical determinations
Oven moisture, %In-house 105-16
65.00.0
10.0
Oven dry matter, %In-house 105-16
35.0100.0
90.0
Crude protein, %AOAC 990.03
8.424.0
21.6
Acid detergent fiber, %Handbook 379
10.229.0
26.1
aNDF, %
NFTA, 199313.3
38.034.2
Total nonstructural
carbohydrates, %Smith, 1983
4.212.0
10.8
Fat, %
AOAC 920.39A1.4
4.03.6
Ash, %
AOAC 942.053.5
10.09.0
Minerals
Calcium, %
NIR ISI equation0.81
2.302.07
Phosphorus, %NIR in-house equation 0.12
0.330.30
Calculated values
Neutral det. soluble
carbohydrates, %Mertens, 1988
8.424.0
21.6
Total digestible nutrients, % Bath & Marble, 1989 21.260.6
54.5
Net energy of lactation, Mcal/lb Mertens leg. ADF0.24
0.680.61
Relative feed valueNFTA, 1993
56.8162.0
146.0
Comments:
Signature:
Understanding laboratory reports Laboratory identification
Should include contact infor-mation (address, fax, phone).
Feed description Theclient needs to provideaccurate and detailedinformation about theforage or feed to aid ininterpretation.
Comments and signature Thereshould be an area where laboratorypersonnel can indicate concerns orprovide other feedback about thesample or results.
Calculated results There should be aclear distinction between resultsdetermined analytically and thosederived or calculated from analyticaldeterminations.
Client identificationHelps ensure infor-mation is reportedto correct personor organization.
Various labs present analysis results in different ways,but the following items should be included.
Lab certificationThis seal indicates thelab has passed theNFTA proficiency test.
Analytical results Resultsshould be reported on a100% dry matter (DM)basis. Additional columnsmay be included forreporting results on anas-is (as-received) or anair-dry (90% DM) basis.
Sample identityand descriptionReport should listlot identificationnumber, samplingdate, samplemethod andhandling, and condition of thesample on arrival.
Matching forage quality to animal needs
Animal performance is determinedby feed availability, feed nutrientcontent, intake, extent of diges-
tion, and metabolism of the feeddigested, but availability and intakemost often determine animal per-formance. A cow never produced milkor a steer never grew on feed that itdidn’t eat!
With regard to the nutritive content offorage, digestible energy (digestibility)is the most common limiting factor.However, there are times whenprotein and minerals are the nutrientsthat limit animal performance, espe-cially in grazing situations when sup-plementation is impractical.
The amounts of digestible energy,protein, vitamins, and mineralsneeded for maintenance is lowrelative to other animal processes. Ingeneral, forages that contain less than70% NDF and more than 8% crudeprotein will contain enough digestibleprotein and energy, vitamins, andminerals to maintain older animals.Thus, even many low quality foragesand crop residues can meet the main-tenance needs of some classes ofanimals, if protein and minerals areadequate.
ReproductionReproduction requires relatively smallincreases in nutrient requirements.Conception of females is oftenenhanced by “flushing” (increasedenergy intake during the breedingseason). Males also need additionalenergy for the increased activityduring the breeding season. Thus,during breeding, animals shouldreceive forages that are 10 to 20%higher in digestible energy, and lowerin NDF, than those fed to animals on amaintenance ration. During thebreeding season, males often loseweight that must be recovered later.
The fetus and uterine tissues requirelittle energy, protein, or mineralsduring the first two-thirds of preg-nancy. Therefore, early pregnancy(gestation) is a time when nutritionalrequirements of animals are low.
During the last third of pregnancy,nutrient requirements increase becausefetal weight increases rapidly. Also,females typically need to store fatduring pregnancy that will be used tomeet the high-energy demand of earlylactation. Not only do nutrient require-ments increase, the internal body spacefor the digestive tract is greatly reducedduring the latter stages of pregnancy.Thus, in the last 10% of pregnancy it isimportant to increase dietary nutritionsubstantially (<50% NDF and at least 10to 12% crude protein).
12
HOW TO PROPERLYSAMPLE PASTUREFORAGESampling pasture forage is espe-cially challenging because thequality of pasture forage is con-stantly changing. Also, selectivegrazing by animals affects thequality of their diets.
If pastures are rotationallystocked, collect forage randomlyfrom several spots so the entirepasture will be represented. It maybe helpful to observe how theanimals are grazing their presentpasture, then collect a sample tothe same stubble height from thenext pasture.
For a continuously stockedpasture, forage should be col-lected from several locations. Notewhether animals are spot grazingand try to sample what they areeating. The pasture can besampled monthly or as needed.
Mix the collected forage, then fillthe sample bag. If not mailedimmediately, refrigerate or air dry.
GrowthThe bodies of very young animals arerapidly developing muscle and bone.Muscle is primarily protein, and boneis mostly minerals (calcium and phos-phorus), so growing animals havemuch higher requirements for crudeprotein and minerals than olderanimals.
Extra energy is also needed for thedevelopment of both muscle andbone, but younger animals have lessinternal body capacity to accommo-date consumption of bulky foragethan older animals. Higher require-ments and less capacity result in theneed for greater nutrient density inthe diets of young, growing animals,especially until they reach about 50%of their mature weight.
Nutrient and energy density of thediet should be highest shortly afterbirth (16 to 18% crude protein and 30to 40% NDF), and gradually decreaseto 12% crude protein and 55% NDF bythe time they reach 50% of matureweight. Milk produced by the motheris an excellent supplement for younganimals that allows them to performwell when consuming forages.
After weaning, the protein in foragesmay be too soluble and may lack theamino acid balance needed for muscledevelopment, or calcium and phos-phorus levels in forage may not beadequate. Thus, supplementing foragediets with protein and minerals oftenimproves the rate of growth in younganimals.
FatteningBody fat becomes the major compo-nent of weight gain as an animalmatures, because the development ofmuscle and skeleton greatly dimin-ishes. Fat is a concentrated source ofenergy; therefore, the fattening ofanimals requires a diet that is dense indigestible energy and lower inprotein, minerals, and vitamins.Fattening diets typically contain 8 to10% crude protein and less than 25%NDF, which is difficult to achieve withall-forage diets because the fiber con-centration in forages limits theirdigestible energy density.
LactationLactation places the greatest nutrientdemand on animals. On a dry basis,milk contains about 20 to 25% protein,25 to 30% fat, and high levels ofminerals and vitamins to ensure therapid growth of offspring. Whereasgrowth and fattening may requirenutrients at one and a half to two timesthe maintenance level, lactation ofbeef cows or sheep may require nutri-ents at two to two and a half timesmaintenance, and lactating dairycows, ewes, and goats may requirenutrients at up to four to five timesmaintenance levels. Such high nutrientdemands necessitate the feeding ofhigh quality forages and/or feeds.
Lactating dairy animals require adelicate balance of fiber: too muchfiber lowers energy density and limitsintake, resulting in low milk produc-tion; too little fiber reduces produc-tion of fat-corrected milk, increasesfattening of the female, and increasesincidence of digestive and metabolicdisorders. To maximize forage use inthe rations, fiber intake must bepushed to the maximum limit of theanimal that will still allow it to realizeits milk production potential. Sincetoo much fiber intake becomes thelimiting factor in this situation, feedinghigh quality forage is critical whenattempting to maximize forage intakeby animals with high levels of milkproduction.
Diets of nursing cows and sheep atpeak lactation need to contain 12 to14% crude protein and less than 55%NDF. However, high-producing lactat-ing dairy cows, ewes, and goatsrequire diets that are 16 to 18% crudeprotein, 25 to 30% NDF, and containsignificant levels of calcium and phos-phorus. As in the case of fatteninganimals, this is difficult to attain withforages alone.
In most cases, the intake potential anddigestible energy content of the foragedetermines the productivity of ananimal. However, when forage quality islow and forages are the only source ofnutrients, protein and minerals maylimit animal performance.
13
An illustration of how well various cat-egories of forage crops tend toprovide digestible dry matter toselected classes of livestock isprovided in figure 8. More detail onnutrient needs of animals can befound in the publications of theNational Research Council, availablefrom National Academy Press.
Economic impactsof forage quality
There is widespread recognitionthat forage generally supplies a rel-atively low-cost source of nutrition
for livestock. However, the relationshipbetween forage quality and the levelof profit realized from forage-relatedenterprises is often underappreciated.
Pasture forage qualityGrazing can provide low-cost nutritionbecause livestock, rather than expen-sive machinery, harvest the forage.However, failure to make adjustmentsto changes in pasture growth rateduring the grazing season may lead toeither overgrazing (which reducesforage growth and may thin foragestands) or undergrazing (which lowersoverall forage quality and increasesforage waste). Consequently, grazingmanagement can be extremelyimportant.
The influence of maturity on foragequality provides another reason forusing pasture when feasible (figure 9).The data compares the percent drymatter, crude protein, and totaldigestible nutrient of selected grassesat three stages of growth: vegetative(as in a properly grazed pasture), boot(when most hay should be harvested),and mature (when much hay actuallyis harvested). For each species, foragequality was highest at the vegetativestage. Thus, grazing not only avoidsmechanical harvesting costs, but alsooften offers the advantage of higherforage quality as compared to storedfeed.
14
U N D E R S T A N D I N G F O R A G E Q U A L I T Y
DM CP TDN
con
stit
uen
t (%
)
DM CP TDN DM CP TDN
Tall fescue Orchardgrass
vegetativebootmature
0
10
20
30
40
50
60
70
80
0
10
20
30
40
50
60
70
80Bermudagrass
0
10
20
30
40
50
60
70
80
Figure 9. Forage quality dry matter (DM), crude protein (CP), and total digestible nutrients (TDN)percentages at varying growth stages.
Source: Adapted from Kennedy, Mark, and John Jennings. 1997. Forage quality in Management Intensive Grazing in the Ozarks.Jointly published by the Top of the Ozarks and the Southwest Missouri R C & D Councils, the Missouri Department of Natural Resources,and the Natural Resources Conservation Service.
% d
iges
tib
le d
ry m
atte
r
warm-seasonperennial
grasses
cool-seasonperennial
grasses
cool-seasonannual grasses
legumes
80
70
60
50
40
dairy cow, 50 lb milk/day
450 lb steer, average daily gain 1.5 lbfirst calf heifer
beef cow/calf to wean 500 lb calf
dry pregnant cow, gaining condition
Source: Adapted from H. Lippke and M.E. Riewe. 1976. Principles of grazing management.In Grasses and Legumes in Texas (E.T. Holt, ed.) Texas Agric. Exp. Stn. Res. Monograph RM6C:169–206.
Figure 8. Forage digestibility ranges and their suitability for differentclasses of livestock.
Hay qualityHay quality varies due to numerousfactors discussed earlier in this publi-cation. Such differences should in turnbe reflected in sale prices when hay ismarketed. This occurred at hayauctions in Wisconsin and California(illustrated in “Importance of ForageQuality” sidebar on page 1).
Other considerationsImproving forage quality can result inother benefits that affect profit.Animal health, including resistance toparasites and diseases, is favored by ahigh plane of nutrition. In addition, thereproductive efficiency of animals isoften higher when nutritive intake ishigh. High quality forage also oftenreduces or eliminates the need forsupplemental feeds, which usually aremore expensive than non-foragesources of nutrition.
Additional informationThe following web sites containinformation about forage quality.
American Forage and GrasslandCouncil: www.afgc.org
Forage Information System:www.forages.orst.edu
National Forage Testing Association:www.foragetesting.org
US Dairy Forage Research Center:www.dfrc.wisc.edu
15
■ The ultimate measure of foragequality is animal performance.
■ Factors having the greatest impacton forage quality are foragespecies, stage of maturity atharvest, and (if forage is mechani-cally harvested) harvesting andstorage techniques.
■ Forage quality varies greatlyamong and within forage crops,and nutritional needs vary amongand within animal classes andspecies. Knowing forage qualityand animal nutritional needs isnecessary to formulate rations thatresult in desired animal perform-ance.
■ Leaves are higher in quality thanstems; young stems are higher inquality than old stems; and greenleaves are higher in quality thandead leaves. In most cases, higherquality is also associated withlegumes as compared to grasses;and with cool-season plants ascompared to warm-season plants.
■ Rain during field drying damageslegume hay more than grass hay.Also, the dryer the hay when rainoccurs, the greater the damage.However, delayed harvest due toconcern about rain probablyresults in more forage quality lossthan does rain damage.
■ Fertilizing with nitrogen generallyincreases the crude protein level ofgrasses, but fertilization usuallyhas little or no effect on thedigestible energy of forage.
■ Sensory evaluation of forageprovides important information,but laboratory testing is requiredto formulate rations.
■ A laboratory analysis uses only afew grams of material to representtons of forage. Therefore, samplingtechnique is extremely important.
■ The numbers provided on a foragetest report are valuable but notabsolute. Reported results varysomewhat due to differenceswithin a hay lot (or other feedmaterial sampled), sampling tech-nique, and laboratory procedures.
■ While protein and minerals canlimit animal performance,digestible energy is more likely tobe the limiting factor from forage.
■ The more mature and fibrous(lower in quality) a forage, thelonger it takes to be digested andthe less an animal will consume.
■ Major losses in forage qualityoften occur due to poor storageand feeding techniques. Producingforage with good nutritive value isnot enough; good animal perform-ance results when animalsconsume forage that is suitablyhigh in nutrients and low in fiber.
KEY CONCEPTS TO REMEMBER
GlossaryAcid detergent fiber (ADF) The residue
remaining after boiling a foragesample in acid detergent solution. ADFcontains cellulose, lignin and silica, butnot hemicellulose. Often used to calcu-late digestibility, TDN and/or NEl.Contrast with crude fiber and neutraldetergent fiber.
Acid detergent fiber insoluble nitrogen(ADFIN) See acid detergent insolublenitrogen (preferred term).
Acid detergent fiber crude protein(ADFCP) See acid detergent insolublecrude protein.
Acid detergent insoluble crude protein(ADICP) The same feed fraction asADIN that has been converted tocrude protein equivalent by multiply-ing ADIN * 6.25. Same as acid detergentfiber crude protein.
Acid detergent insoluble nitrogen(ADIN) Nitrogen in acid detergentfiber residue. ADIN greater than 15% ofnitrogen is an indicator of heatdamage. Formation of ADIN is alsocalled non-enzymatic browning(because the hay or silage turnsbrown) or the Maillard reaction. Shouldbe expressed as a percent of the drymatter (preferred) or of the nitrogen,not of ADF. Same as acid detergent fiberinsoluble nitrogen.
Acid insoluble lignin Lignin measuredusing sulfuric acid. See lignin.
Adjusted crude protein (ACP) A calcu-lated value adjusting total crudeprotein for heat-damaged protein.Adjusted crude protein estimates theprotein available for animal use andshould be used for formulating rationswhen ADIN is greater than 15% of thetotal nitrogen.
Ash (also called total ash) A measure ofthe total mineral content; the residueremaining after burning a sample.Values above 10% for grasses or 14%for legumes usually indicate soil con-tamination of forage. Ash, ADF-ash,and NDF-ash will be different valuesbecause ADF and NDF proceduresremove some minerals.
As fed See as is.
As is Values expressed based on moisturecontent of forage when it was receivedin the laboratory. Same as as fed and asreceived.
As received See as is.
Available crude protein (ACP) Same asadjusted crude protein.
Bypass protein See rumen undegradedprotein.
Cellulose A structural carbohydrate; along-chain polymer of glucose that isthe main constituent of plant cellwalls. It is the most abundant carbohy-drate in nature and is slowly and par-tially digestible by ruminants.
Crude fat An estimate of the fat contentof feeds that is measured by etherextraction. Crude fat contains true fat(triglycerides) as well as alcohols,waxes, terpenes, steroids, pigments,ester, aldehydes, and other lipids. Seeether extract and fat.
Crude fiber (CF) The original fibermethod using sequential acid andalkali extraction (developed byHenneberg and Sttohmann in 1865).Crude fiber includes most of the cellu-lose, but only a portion of the ligninand no ash. Therefore it underesti-mates true fiber and is less than ADF. Itis seldom used for forage analysis.Contrast with acid detergent fiber andneutral detergent fiber.
Crude protein (CP) This value is 6.25 timesthe nitrogen content for forage or 5.7times the nitrogen content for grain.
Degraded intake protein (DIP) Seerumen degraded protein.
Digestible cell wall See digestible neutraldetergent fiber (preferred term).
Digestible neutral detergent fiber(dNDF) The portion of the neutraldetergent fiber digested by animals ata specified level of feed intake. ThedNDF of feeds may be determined byin vivo feeding trials or estimated bylignin analysis, in vitro or in situdigestibility, or by near infraredreflectance analysis.
Digestible energy (DE) The energy in aforage or feedstuff that is not excretedin feces.
Dry matter (DM) The percentage of thesample that is not water.
Dry matter digestibility (DMD) Theportion of the dry matter in a feed thatis digested by animals at a specifiedlevel of feed intake. Called in vivo DMDif determined by feeding animals in adigestion trial. There is no laboratorymethod for measuring DMD directly; itis often estimated by measuring in
vitro digestibility, in situ digestibility,near infrared reflectance analysis, orcalculated from acid detergent fiber(the least accurate method of determi-nation).
Escape protein See rumen undegradedprotein.
Ether extract (EE) Portion of dry matterextracted with ether. Used to measurecrude fat. See crude fat and fat.
Fat Triglycerides of fatty acids that are ahigh density source of energy foranimals. Fat is measured by determin-ing content of fatty acids or is esti-mated in forages as ether extractminus one. Fats and fatty acids contain2.25 times the energy found in carbo-hydrates and are highly digestible byanimals. See ether extract and crude fat.
Forage quality The ability of a forage tosupport desired levels of animal per-formance (e.g., daily gain or milk pro-duction). It is a function of voluntaryintake and nutritive value.
Hemicellulose Long chains of sugar com-pounds associated with plant cell walls.
In vitro digestibility See in vitro drymatter digestibility (preferred term).
In vitro dry matter digestibility (IVDMD)Digestibility determined by incubationof a ground forage sample with rumenfluid in beaker or test tube for 24 to 48hours, followed either by addition ofacid and pepsin and further incuba-tion for 24 hours (IVDM or IVDMD) orby boiling in neutral detergent fibersolution. See dry matter digestibility.
In vitro NDF digestibility (IVDNFD) Seedigestible neutral detergent fiber.
In situ digestibility Digestibility deter-mined by incubation of a groundforage sample in a porous nylon bagwithin rumen of an animal for a fixedtime period.
Lignin Undigestible plant component,giving the plant cell wall its strengthand water impermeability. Lignin alsoreduces digestibility.
Metabolizable energy (ME) The energyin a forage that is not lost in feces,urine, or rumen gases.
Metabolizable protein (MP) The rumenundegraded protein and microbial pro-tein that passes into the intestine andcan be broken down into amino acids.
16
U N D E R S T A N D I N G F O R A G E Q U A L I T Y
17
Modified crude fiber (MCF) A modifica-tion of the crude fiber in which theashing step is deleted. Modified crudefiber is crude fiber plus ash.
Moisture The percent of the sample thatis water.
Net energy for gain (NEg) An estimate ofthe energy value of a feed used forbody weight gain above that requiredfor maintenance.
Net energy for lactation (NEl) Anestimate of the energy value of a feedused for maintenance plus milk pro-duction during lactation and for main-tenance plus the last two months ofgestation for dry, pregnant cows.
Net energy for maintenance (NEm) Anestimate of the energy value of a feedused to keep an animal at a stableweight.
Neutral detergent fiber (NDF) Residueleft after boiling a sample in neutraldetergent solution. Called aNDF ifamylase and sodium sulfite are usedduring the extraction (this is recom-mended procedure). The NDF inforages represents the indigestible andslowly digestible components in plantcell walls (cellulose, hemicellulose,lignin, and ash). Contrast with crudefiber and acid detergent fiber.
Neutral detergent insoluble crudeprotein (NDICP) Nitrogen in neutraldetergent fiber residue. Estimates theportion of the undegradable proteinthat is available to the animal.
Neutral detergent soluble carbohydrates(NDSC) See nonfibrous carbohydrates.
Neutral detergent solubles (NDS) Theportion of the forage that is soluble inneutral detergent solution and there-fore is not neutral detergent fiber.Usually assumed to be 98% digestible.
Neutral detergent soluble fiber (NDSF)Neutral detergent soluble materialundigestible by animal enzymes.
Nonfibrous carbohydrate (NFC) Anestimate of the rapidly available carbo-hydrates in a forage (primarily starchand sugars). This value is calculatedfrom one of the following equations:NFC = 100% – (CP% + NDF% + EE% +Ash%) or, if corrected for NDFCP,NFC% = 100% – [CP% + (NDF% –NDFCP%) + EE% + Ash%] Contrastwith total nonstructural carbohydrate.
Non-protein nitrogen (NPN) The portionof the total nitrogen that is not inprotein. If high, NPN is an indicator ofpotential for nitrate toxicity.
Nonstructural carbohydrate (NSC) Seetotal nonstructural carbohydrate;contrast with nonfibrous carbohydrate.
Nutritive value (NV) Protein, mineral, andenergy composition, availability ofenergy, and efficiency of energy utiliza-tion.
Organic matter (OM) The portion of thedry matter that is not ash (mineral).
Organic matter digestibility (OMD) Theportion of the organic matter that isdigestible.
Protein A long chain of amino acidsessential for plant and animal life.Animals meet protein needs bybreaking down plant and microbial(from the rumen) protein and reassem-bling as animal protein.
Relative feed value (RFV) An index forranking cool-season grass and legumeforages based on combiningdigestibility and intake potential.Calculated from ADF and NDF. Thehigher the RFV, the better the quality. Itis used to compare varieties, matchhay/silage inventories to animals, andto market hay.
Rumen degraded protein (RDP) Thatportion of total protein that isdegraded to ammonia in the rumen.Same as degraded intake protein.
Rumen degraded protein is the pre-ferred term.
Rumen undegraded protein (RUP) Thatportion of the protein not degraded inthe rumen. While often called bypassprotein, escape protein, or undegradedintake protein. Rumen undegradedprotein is the preferred term.
Soluble intake protein (SIP) That portionof total protein rapidly degraded toammonia in the rumen.
Soluble protein Protein soluble in a spec-ified solution. Can be used to estimaterumen degraded protein and rumenundegraded protein.
Total digestible nutrients (TDN) Thesum of crude protein, fat (multiplied by2.25), non-structural carbohydrates,and digestible NDF. TDN is often esti-mated by calculation from ADF. Theformulas for calculating TDN vary byregion and by nutritionist.
Total nonstructural carbohydrate (TNC)A measure of the starch and sugar inforages. It has a lower value than nonfi-brous carbohydrates because NFCcontains compounds other than starchand sugars. Same as nonstructural car-bohydrate; contrast with nonfibrouscarbohydrate.
Undegraded intake protein (UIP) Sameas rumen undegraded protein.
Voluntary intake Consumption of aforage when forage availability is notlimiting.
analytical fractions chemical constituents other analyses
moisture waterash various minerals plus sand
dry organic NDF ADF cellulosematter matter lignin
fiber-bound N* ADICP, NDICPheat-damaged N*hemicellulosefructans
NDS glucans NDSFNDSC pectic substances
sugarsstarchesorganic acidsNPN (amino acids, amines,
urea)crude degradable RDP (DIP)protein true protein
undegradable RUP (UIP)ether esterified fatty acidsextract pigments and waxes
*Fiber-bound nitrogen and heat-damaged nitrogen are also found in crude protein and RUP.
Source: John Moore. Professor Emeritus of Animal Sciences, University of Florida.
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Figure 10. Feed and forage composition.
Authors Dr. Don Ball
Extension Agronomist/Alumni ProfessorAuburn University
Dr. Mike CollinsProfessor of AgronomyUniversity of Kentucky
Dr. Garry LacefieldExtension Agronomist/ProfessorUniversity of Kentucky
Dr. Neal MartinDirector, U.S. Dairy ForageResearch CenterUSDA/ARS
Dr. David MertensDairy Scientist, U.S. Dairy ForageResearch CenterUSDA/ARS
Dr. Ken OlsonDairy & Animal Health SpecialistAmerican Farm Bureau Federation
Dr. Dan PutnamExtension AgronomistAssociate ProfessorUniversity of California-Davis
Dr. Dan UndersanderExtension Agronomist/ProfessorUniversity of Wisconsin
Mr. Mike WolfJL Analytical ServicesModesto, California
ReviewersThe authors gratefully acknowledge reviewsof this publication provided by:
Dr. Larry ChaseAssociate Professor of Animal SciencesCornell University
Dr. Marvin HallExtension Agronomist/ProfessorPenn State University
Dr. Mike HutjensExtension Dairy SpecialistProfessor of Animal SciencesUniversity of Illinois
Mr. Paul MeyerCommercial hay producerWest Point, Nebraska
Dr. John MooreProfessor Emeritus of Animal SciencesUniversity of Florida
Mr. Steve OrloffExtension Farm AdvisorYreka, California
Photography creditsDon Ball
Garry Lacefield
Steve Orloff
SponsorsPrinting of this publication was funded bythe following organizations:
ABI Alfalfa, Inc.Agway Farm SeedA.L. GilbertAmerican Farm Bureau FederationAmerican Farm ProductsANKOM TechnologyBarenbrug USABASF CorporationCase IHCelPrilCROPLAN GENETICSForage Genetics InternationalFoss North America, Inc.Grazing Lands Conservation InitiativeHeston/New Idea – AGCO CorporationIMC Global, Inc.Land O’ Lakes Farmland FeedMississippi Chemical CorporationMycogen SeedsNatural Resources Conservation ServiceNew Holland North America, Inc.Pennington Seed, Inc.Pioneer Hi-Bred International, Inc.Purina Mills, Inc.Research Seeds, Inc.SeedbioticsServi-Tech Labs/ Dodge City,
KS & Hastings, NEState Farm Bureaus of Iowa, Idaho, Kansas,
Michigan, Nebraska, New Mexico,Oklahoma, South Dakota, Tennessee,Texas, and Utah
Vermeer Manufacturing Co.Vigortone Ag ProductsWilliam H. Miner Agricultural Research
InstituteWL Research
Ball, D.M., M. Collins, G.D. Lacefield, N.P. Martin, D.A. Mertens, K.E. Olson, D.H. Putnam,D.J. Undersander, and M.W. Wolf. 2001. Understanding Forage Quality.American Farm Bureau Federation Publication 1-01, Park Ridge, IL
This publication has been endorsed by the American Forage and Grassland Council, the National Forage Testing Association,and The National Hay Association.
Understanding forage qualityDon Ball
Mike Collins
Garry Lacefield
Neal Martin
David Mertens
Ken Olson
Dan Putnam
Dan Undersander
Mike Wolf
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