ADM: Understand Your Feed Analysis Report - AgroMedia

1 1R1:1 Understand your feed Analysis ReportProtein fractionsOne of the first values most of us look for whenwe receive a forage Analysis Report is CrudeProtein (CP) %. Since most feed proteins containabout 16% nitrogen (N), CP % is estimated in thefeed lab by measuring the % of N in the feed andmultiplying that value by - the inverse of 16%(1 / = ). However, some portion of theN in most feeds is found as non-protein nitrogen(NPN) and, therefore, the value calculated bymultiplying N x is referred to as crude ratherthan true protein (see article 1P1).Most feed labs will also measure the levels ofseveral subfractions of crude protein that can beuseful in formulating dairy rations. One of thesefractions is acid detergent insoluble protein (ADIP%), used to estimate the amount of protein whichis unavailable to the animal due to heat silage is put up too dry (greater than 50%dry matter) or hay too wet (less than 85% drymatter), excessive heating may cause some of theprotein to become irreversibly bound to severity of damage is estimated in the feedlab by measuring the amount of crude proteinassociated with the acid detergent fibre (ADF)fraction.

2 Depending on the feed lab used, thisfraction may be reported as acid detergentinsoluble nitrogen (ADIN %), acid detergent fibreprotein (ADF-P %) or acid detergent fibre nitrogen(ADF-N %). Values reported as N % can beconverted to protein % by multiplying by , asexplained protein estimates the amount of crudeprotein which will readily dissolve when the feedenters the rumen. It is assumed that this fractionrepresents crude protein which is rapidly degradedby rumen microbes (see article 1P1 for anexplanation of protein degradability). The CP ofmost forages is 40-50% soluble. Higher solubleprotein levels are often found in silages which areput up very wet (less than 30% dry matter). Whenthis is the case, the bypass protein value of theforage should be % is also a nitrogen-containing feedfraction, but it contributes very little to CP %.

3 Nitrates can accumulate in a crop which has beenIn October and November every year, a largeproportion of our work involves formulation ofwinter feeding programs, based on Analysis resultsof the new forage crops. When discussing thoseresults with our clients, it is apparent that themeanings of many of the values are not clearlyunderstood. Here is a brief explanation of each ofthe numbers you are likely to find on your forageanalysis Report :Moisture and Dry MatterMoisture % indicates the proportion of water inthe sample, calculated by weighing the samplebefore and after complete drying. For example, ifa sample of silage weighs 100 grams beforedrying and 40 grams after, it is assumed that 60grams of water were lost - the original sample wastherefore 60% moisture.

4 Conversely, the DryMatter % of the sample was 40%.Most feed labs Report Analysis results on both awet and a dry basis. The wet basis may bereferred to by the terms: As Is, As Fed or AsReceived. The 100% dry basis is usually referredto as: Dry, DM (Dry Matter), Dry Basis or DryResult. We'll use the terms As Fed and DM in theremainder of this article. You can convert fromone basis to the other using the followingformulas:As Fed basis=DM basisx(Dry Matter % / 100)DM basis =As Fed basis(Dry Matter % / 100)When we formulate rations for dairy cattle, weuse Analysis results quoted on a DM , when we are discussing the quality of aparticular forage, we normally talk about itsanalysis on this basis also. However, you shouldbe aware that the Analysis guarantees onmanufactured feeds are stated on an As Fed you are not given a Moisture % or Dry Matter %for the product, you can assume it is 90% drymatter.

5 Before using manufactured feeds in aration formulation, convert their Analysis levels tothe DM basis using the second formula example, a 16% Dairy Ration will crude protein [16 / (90/100)] on a START1R1:2 The Dairy Extension Advisory Group encourages the distribution of Alberta Dairy Management articlesbut requests that permission for direct reference to or use of these articles be obtained in to frost, drought or high levels of nitrogenfertilization. Feeds containing high levels of nitrate(greater than 1%) can be toxic, particularly when firstoffered to animals not adapted to and NDFAcid detergent fibre (ADF %) is a measure of themost slowly digestible components of a forage. Sincethe digestibility of a feed determines its energy value,the primary use of ADF % is in the calculation of NetEnergy for lactation (NEl) and all of the other energyvalues reported (see below).

6 Neutral detergent fibre (NDF %) is a morecomplete measure of forage fibre than ADF % and,therefore, its value must always be higher. Thedifference between ADF % and NDF % is normallygreater for grasses and cereal silages than it is forlegumes such as ADF % and NDF % are chemical measures offibre. The measured levels will be the same for along hay as they would be for the same hay if it werefinely ground. Since dairy cattle require bothphysical (chewable) and chemical fibre, chemical feedanalysis results must be combined with an assessmentof particle size to provide a complete estimate of afeed's fibre value. A few feed labs offer particle sizeanalysis, but most commonly the assessment is basedon subjective visual evaluation. Dairy rations arecommonly formulated to provide minimum levels ofeffective NDF or forage NDF, estimates whichcombine both chemical and physical attributes feed labs offer analyses of the importantmacro- (Sodium (Na), Potassium (K), Calcium (Ca),Magnesium (Mg), Phosphorus (P), Chloride (Cl) andSulphur (S) ) and micro- (trace) minerals (Copper(Cu), Manganese (Mn), Selenium (Se) and Zinc (Zn).)

7 However, we routinely only test for Ca, P, K and Mgsince these are the most variable in our of these minerals by Near InfraredReflectance Spectroscopy Analysis (NIR, NIRA orNIRS), although less expensive, is considered lessaccurate than Analysis by 'wet chemistry'. But forroutine use, we have found the NIR values to be rations are generally formulated to supplytrace minerals (and vitamins) through supplementalsources at levels well above minimum , it is seldom considered necessary tomeasure levels of these minerals in routine Analysis formulating rations for cation-anion balance(DCAB - see article 1M1), it is essential that levels ofNa, K, Cl and S be measured by wet rations for dry cows that have not been verycarefully balanced have created as many problems asthey have valuesSeveral of the values normally found on a feedanalysis Report are calculated from the Analysis valuesdiscussed above.

8 And the formulas used for thesecalculations vary from lab to lab. However, the waythat these values are used is typically more critical tothe success of a ration formulation than the absolutevalues reported. your nutritionist should be quitefamiliar with their correct or Available Crude Protein % (ACP %) iscalculated by subtracting a variable portion(depending on the lab) of ADIP % from CP %. SinceADIP normally accounts for 5-10% of CP even innon-heat damaged feeds, some labs do not adjust CP %until ADIP % exceeds 9-10% of CP %. Otherssubtract all ADIP % from CP %, on the basis thanhigh feed throughput by lactating dairy cows limitstheir opportunity to digest fibre-bound feed Value (RFV) is an index of foragequality calculated from ADF % and NDF % using thefollowing formula :RFV=[( - ( x ADF %)) x (120 / NDF %)] that RFV does not account for the CP % ofthe forage.

9 It is based only on fibre levels and is,therefore, an index of forage mentioned above, all energy values reported(TDN, NEl, NEm, NEg, DE, ME) are calculated fromADF % using formulas specific for each forage type -grass, legume, grass/legume mix, small cereal or cornsilage. It is, therefore, very important to identify theforage type to ensure that the correct equation is by :Steve Mason, : Nutrition / Management SpecialistsCalgary : 284-5484