Feed-Valu Services®️ Report Definitions

Moisture (% as is)
Moisture is the inverse of DM.

Dry Matter (% as is)
The moisture/DM content of the silage is probably the biggest variable impacting silage quality. Wet silages (less than 30% DM) are prone to seepage and Clostridial or acetic fermentations, which are wasteful in terms of DM and energy. Dry silages have more pores throughout the silage mass, which can mean more oxygen pockets and more spoilage. In corn silage, dry silages typically have lower digestibilities, but higher starch content because it is reflective of a more mature plant. Drier silages also undergo a stunted fermentation, which can result in less overall acids.

pH
pH is a measure of the degree of acidity. In silage, a low pH (higher acidity) will inhibit the growth of undesirable microorganisms such as Clostridia and Enterobacteria. It is important that the pH drop low and quickly, early during the fermentation process. To ensure that this happens, cover the silo quickly and well to eliminate all oxygen and begin fermentation. A low pH will also reduce protein degradation. A pH higher than normal means the silage did not ferment well or it is unstable/spoiled. This could be due to high yeast levels, low moisture content of harvested forage, lack of sufficient substrate for bacteria to make acids, undesirable fermentation, such as Clostridia, oxygen entering the silage mass (i.e. poor packing), cold environmental conditions that stunt fermentation (i.e. late fall harvesting), or unstable forages with poor bunk life.

Crude Protein (% DM)
Crude protein is simply the amount of nitrogen (N) within a feed x 6.25. The 6.25 factor is derived from the concentration of N in amino acids, which averages 16.0% (100/16.0 = 6.25). The concentration of N in the amino acids of different feeds is, however, slightly different. Thus, crude protein can slightly over- or underestimate true N. Crude protein determination is highly accurate by multiple methods, including NIRS.

Adj Crude Protein (% DM)
When AD-ICP is >10% of the CP in a forage, there is a much higher probability the CP within the ADF is unavailable to the animal. In these situations, the AD-ICP is often substracted from the CP, yielding Adjusted Crude Protein. Acid detergent insoluble crude protein (AD-ICP), or the amount of protein bound within ADF, is commonly used to estimate the heat damage in forages. Typically <10% of the CP is bound within ADF. All forages contain some AD-ICP; in unheated hays, this probably comprises 4-8% of the total CP. In native origin form, AD-ICP is largely indigestible by ruminants, but research suggests that AD-ICP produced as a result of heating also has low bioavailabilities. When Adj Crude Protein is the same as CP (or blank), this means higher levels of AD-ICP were not detected. If Adj Crude Protein is lower than CP, this means significant quantities of AD-ICP were found, which could have detrimental effects on CP digestion and, in addition, could have serious detrimental effects of forage energy levels.

AD-ICP (% DM)
Acid detergent insoluble crude protein (AD-ICP) is the amount of protein bound within ADF. AD-ICP is commonly used to estimate the heat damage in forages. Typically <10% of the CP is bound within
ADF. All forages contain some AD-ICP; in unheated hays, this probably comprises 4-8% of the total CP. In native origin form, CP in ADF is largely indigestible within ruminants, but research also suggests that CP in ADF produced as a result of heating also has low bioavailabilities. When AD-ICP is >10% of the CP in a forage, there is a much higher probability the CP within the ADF is unavailable to the animal. In these situations, the AD-ICP is often substracted from the CP, yielding Adjusted Crude Protein.

ND-ICP (% DM)
Neutral detergent insoluble crude protein (ND-ICP) is the amount of protein bound within NDF. NDICP is commonly used in models or calculations and is not a common ration formulation nutrient. For example, ND-ICP is often subtracted from NDF in summative equations to yield protein-free NDF. In some ration models ND-ICP - AD-ICP is calculated and considered a slowly digested B protein fraction.

Soluble Protein (% CP)
Soluble protein is the amount of protein that is soluble in a borate phosphate buffer. Soluble protein is a benchmark of rumen undegraded protein and starch digestibility. Proteins in forages become more or less soluble due to maturity and ensiling. Corn, legume or grass silages range in soluble protein from 25% to 75% of protein. In general, the greater the CP content, the wetter the silage and the longer the ensiling period, the greater the protein solubility. Dry legume and grass forages have far less soluble protein because proteins are not broken down via proteolysis during fermentation. Proteins in dry legume and grass forage are typically 20-40% soluble. Soluble protein can also be used as benchmark of starch digestibility in corn silage and high moisture corn. When soluble protein exceeds 50% of protein, it is an indication that a majority of the proteins in the corn kernel have been degraded thus making the starch more available.

Ammonia-N (% of CP equivalent)
Ammonia is the result of degradation of the amino acids in plant proteins, which is usually due to protease enzymes in the silo. The two main times that ammonia forms are during the initial fermentation and during storage. Ammonia formation during the upfront fermentation is undesirable, as it generally reflects DM losses, protein wasting, and an overall slow and undesirable fermentation (such as a Clostridial or butyric fermentation). During storage, ammonia levels of alfalfa, in general, do not increase, but ammonia levels of corn silage do increase during storage, due to degradation of the prolamin protein matrix that surrounds starch within the corn granule. Thus, in corn, ammonia level increases reflect increases in starch digestibility.

ADF (% DM)
ADF is the fiber residue remaining after boiling a forage sample in acid detergent solution. ADF contains cellulose, lignin and silica, but not hemicellulose. Hemicellulose of a forage can be estimated as (aNDF-ADF). When NDF and ADF differentials are narrow (<7-8 percentage points), the forage likely has low concentrations of hemicellulose. Forages with low hemicellulose concentrations will have lower NDF digestibility because hemicellulose is readily digestible. ADF was historically used in equations to calculate TDN and/or NEL, but newer summative energy estimates have largely replaces old empirical ADF-energy equations.

aNDF (% DM)
aNDF is the residue left after boiling sample in neutral detergent solution. The “a” prior to “NDF” indicates sodium sulfite and amylase were used in the assay. Use of amylase and sodium sulfite are deemed important to remove as much starch and CP contamination out of the NDF fraction as possible. The NDF in forages represents both indigestible and slowly digestible components in plant cell walls (cellulose, hemicellulose, lignin and ash). Ash contamination in aNDF, at times, can be problematic, which has given rise to “ash free NDF”. See aNDFom.

aNDFom (% DM)
aNDFom is neutral detergent fiber organic matter. aNDFom is considered the truest expression of NDF. aNDFom is determined using amylase and sodium sulfite with the ash (mineral) contamination removed. Commonly aNDFom values will be 2-3 percentage units lower than aNDF. However, if the sample is highly contaminated with ash, aNDFom values maybe 5-10 percentage units lower than aNDF. In general, corn silage NDF is not heavily contaminated with ash, but legume, legume-grass and small grain forage NDF may have high levels of ash contamination, which can be reflected in high aNDF concentrations. Thus, ash-free NDF (aNDFom) is used to avoid overestimating NDF concentrations in problematic forages.

Lignin (% DM)
Lignin is a component of NDF. Lignin cross-links and bonds plant cell walls together. Small changes in lignin concentration greatly increase how strongly plant cell walls are bonded together and, thus, lignin is inversely related to NDFD. Legumes contain greater concentrations of lignin (6-8%) as compared to grasses and corn silages (4-5%). Forages such as BMR corn silages are lower in lignin (2-3%) and, correspondingly, BMR corn silages have greater NDF digestibility as compared to normal corn hybrids

NDFD 24 (% NDF)
Neutral detergent fiber digestibility (NDFD 24) is determined by incubating the feed in buffers and rumen fluid for 24 h. The assay, called in vitro true dry matter digestibility (IVTDMD) technically measures indigestible fiber in a forage. What is not digestible (100-IVTDMD) is indigestible fiber (idNDF). The simple equation (NDF - idNDF) converts the amount of NDF that was digested (dNDF). dNDF divided by NDF is the percentage of NDF that was digested (NDFD, 24 h). NDFD, 24 h values are commonly used in models to estimate the rate of NDFD digestion in high-producing lactating dairy cows. While early timepoint NDF digestion rate estimates are logical, challenges occur because, with estimation of NDFD, 24 h, either wet chemistry or NIRS is far more challenging with substantially more laboratory error than 48 h estimates of NDFD. As a result NDFD, 24 h is not a common benchmark of NDF digestibility and is seldom used directly in ration or feed evaluation systems.

NDFD 24 difference (% NDF)
Laboratories often provide a relevant universe reference to other NDFD results. A negative NDFD 24 difference means the NDFD of the sample is lower than other similar type forage samples evaluated at the lab. A positive NDFD 24 difference means the NDFD of the sample is greater than other similar type forage samples evaluated at the lab.

NDFD 30 (% NDF)
Neutral detergent fiber digestibility (NDFD 30) is determined by incubating the feed in buffers and rumen fluid for 24 h. The assay, called in vitro true dry matter digestibility (IVTDMD), technically measures indigestible fiber in a forage. What is not digestible (100-IVTDMD) is indigestible fiber (idNDF). Using the simple equation (NDF - idNDF) converts the amount of NDF that was digested (dNDF). dNDF divided by NDF is the percentage of NDF that was digested (NDFD, 30 h). Corn silage and grass forages ranges from 45 to 65 % NDFD 30 h. Legume forages range from 35-55 % NDFD, 30 h. NDFD, 30 is the most common benchmark of NDF digestibility and is often used in summative equations as a part of estimating total energy in forages.

NDFD 30 difference (% NDF)
Laboratories often provide a relevant universe reference to other NDFD results. A negative NDFD 30 difference means the NDFD of the sample is lower than similar type forage samples evaluated at the lab. A positive NDFD 30 difference means the NDFD of the sample is greater than other similar type forage samples evaluated at the lab.

NDF kd (% hr)
NDF kd is the kinetic rate of aNDFom digestion. Alternatively, and technically, it is how fast the potentially digestible fraction (aNDFom - uNDF240) of NDF digest. Typically, forage NDF kd ranges from 2-10% hr. Legume forages have faster NDF kd than grass forages with corn silage being intermediate. High-NDF byproducts, such as corn gluten feed and soyhulls, will have NDF kd greater than 10% hr.

uNDFom24 (% DM)
Undigested neutral detergent fiber organic matter (uNDFom24) expressed as a % of DM after incubating the feed in buffers and rumen fluid for 24 h. uNDFom24 is not an NDF digestibility term. Rather it represents the total amount of NDF in forage that is difficult to digest in 24 h. To date, the range of uNDFom24 in forages and feeds is relatively unknown. Because uNDFom24 is expressed as a % of DM, inherent lab error may be reduced and, thus, uNDFom24 has potential to help define rates and pools of NDF digestion. uNDFom24 is easier to predict with NIRS as compared to NDF digestibility terms when expressed as a percent of NDF.

uNDFom30 (% DM)
Undigested neutral detergent fiber organic matter (uNDFom30) expressed as a % of DM after incubating the feed in buffers and rumen fluid for 30 h. uNDFom30 is not an NDF digestibility term. Rather it represents the total amount of NDF in forage that is difficult to digest in 30 h. In general, legume and legume grass forages contain approximately 25% uNDFom30. Corn silages contain 15-20% uNDFom30 and straws may contain 40-50% uNDFom30. Because uNDFom30 is expressed as a % of DM inherent lab error is reduced. uNDFom30 has potential to help define rates of NDF digestion. uNDFom30 as a % of DM is easier to predict with NIRS as compared to NDF digestibility terms when expressed as a % of NDF.

uNDFom240 (% DM)
Undigested neutral detergent fiber organic matter (uNDFom240) expressed as a % of DM after incubating the feed in buffers and rumen fluid for 240 h. uNDFom240 is not an NDF digestibility term. Rather, it represents the total amount of NDF in forage that is nearly impossible to digest. uNDFom240 is an alternative lignin-like term and/or represents the total amount of “bad fiber” in a forage. In general, legume forages contain approximately 15-25% uNDFom240. Grass forages such as small grain silages may contain 10-25% uNDF240. Corn silages contain 5-14% uNDFom240 and straws contain 25-30% uNDFom240. Because uNDFom240 is expressed as a % of DM, inherent lab error is reduced. uNDFom240 helps define the amount of aNDFom that is potentially digestible. uNDFom240 as a % of DM is easier to predict with NIRS as compared to NDF digestibility terms when expressed as a % of NDF.

Fat (EE) (% DM)
Lipids (fats) are soluble in organic solvents. The ether extract (EE) procedure is built to wash feed samples with the organic solvent ether to remove lipids and then weigh how much was removed. The problem with extraction in ether solvents (EE) is that compounds other than glycerol based-lipids are extracted. These compounds include nonglycerol-based lipids like waxes and alkenes that have little value for the animal, and non-lipid component like fat-soluble vitamins and pigments. Ether extract analysis results in inflated values of true fat value of a feedstuff.

Fat (TFA) (% DM)
The total fatty acids (TFA) method isolates the true fatty acid portion of glycerol-based lipids. Fatty acids are the energy-rich fraction of fats. Fatty acids also have tissue and rumen effects (reproduction, immune response and milk fat synthesis amongst others). The TFA analysis provides more pertinent information on animal performance and is a more biologically accurate measure of the true fat content of a feedstuff. The TFA content will be invariably less than the ether extract (Fat EE) content of a feedstuff.

Starch (% DM)
Starch is a polysaccharide consisting of a long chain of glucose units ((C6H10O5)n). Starch values range in corn silage and corn grain from 15% to 45% and 65% to 70%, respectively. Starch digestibility is highly variable and ranges from 80 to 98%. Starch can be digested in the rumen, small intestine and large intestine of ruminants. Fecal starch concentrations >3-5% indicate challenges with starch digestibility. Starch is well predicted by NIRS.

Starch kd (% hr)
Starch kd is the kinetic rate of starch digestion. Alternatively, it is how fast starch digest in the rumen. It is typically estimated from a 7-hr in vitro or in situ test. Typically, starch kd ranges from 10 to 30% hr.

IVSD 7 hr (% Starch)
IVSD 7 hr is in vitro starch digestibility after a 7 hr incubation in rumen fluid. IVSD 7 hr is estimated via wet chemisty or NIR calibration and ranks starch digestibility in the following categories of high (>88), medium (88-78) and low (<78). Particle size of the kernels are not considered in IVSD 7 hr. Because kernel particle size can have a major influence on true in vivo starch digestibility IVSD 7 hr values should be used with some caution. IVSD 7 hr should increase with advancing fermentation (storage) time in corn silages, high moisture corn, and snaplage, and can be used to monitor that event. There are no standardized approaches for using IVSD 7 hr in ration formulation.

Sugar ESC (% DM)
Ethanol-soluble carbohydrates (ESC) are carbohydrates that are soluble in 80% ethanol. Ethanolsoluble carbohydrates, extracted in ethanol, are mainly simple sugars, such as glucose and sucrose but not fructans. Crudely, the fructan content of forage can be determined by subtracting ethanol-soluble carbohydrates from water-soluble carbohydrates. Ethanol soluble carbohydrates fraction are fermented very rapidly in the rumen. Dry, well preserved forages will have much higher ESC concentrations as compared to silage because ESC in silage is primarily converted to VFAs.

Sugar WSC (% DM)
Water-soluble carbohydrates (WSC) are carbohydrates that are extracted from a sample by dissolving them in water. Simple sugars and fructans primarily make up WSC. Interpreting and using this value depends on the proportions of sugars and fructans in the sample. Simple sugars are fermented rapidly in the rumen and produce different end-product rumen VFAs, depending on the sugar. Fructans are fermented slower and also have different end-product rumen VFA yield. Fructans are rarely analyzed separately from other WSC. Dry, well preserved forages will have much higher WSC concentrations as compared to silage because ESC in silage is primarily converted to VFAs.

Ash (% DM)
Ash is the total amount of mineral in a feed or forage from all sources. Ash includes minerals within the forage such as Ca, P, K, etc. and external minerals such as silica and clay (soil, dirt). Legume and grass forages are more commonly contaminated with soil and may have high ash concentrations. For legume, legume grass and small grain forages, ash contents >7-8% suggest potential soil contamination. Although uncommon, corn silages >4-5% ash are likely contaminated with soil. Excessive ash in forages is problematic because it is energy-free dry matter in the diets.

Calcium (% DM)
Calcium is essential for living organisms, in particular in cell physiology, and is often considered the “primary” mineral of lactating dairy cows because milk is naturally high in calcium thus calcium requirements of lactating dairy cows are higher than any other species of livestock. Feed and forages contain widely diverse amounts of calcium. Forages such as legumes may contain up to 1.5% calcium while grass contain far less calcium. Calcium content of forages is estimated accurately by NIRS within forages that have a wide range of calcium concentration such as legume grass forages. When calcium concentrations of a forage type are narrow, such as corn silage, Ca concentrations should be confirmed using wet chemistry methods.

Phosphorus (% DM)
Like calcium, phosphorus is essential for living organisms and is a primary mineral associated with energy metabolism and skeletal structure of livestock. In contrast to calcium, forages typically do not have widely ranging P concentrations. In most forages, P concentration will range between 0.20% and 0.40%. Due to a lack of range within forages, NIRS does not predict forage P concentration efficiently. The feeding of excess P can result in excessive P excretion, which has been shown to be environmentally detrimental. Feed byproducts and co-products often contain high P concentrations.

Magnesium (% DM)
Magnesium (Mg) is always challenging to predict using NIR methods. In critical situations, which include transition cow diets and lactating diets high in potassium (K), NIRS and book values for Mg should not be used due to the risk of hypomagnesimia (low blood Mg). In these situations, wet chemistry mineral profiles of all ingredients in the diet are warranted. Transition and high K diets may require 0.40-0.45% Mg. In addition, K:Mg ratios of <4:1 should be monitored and or maintained.

Potassium (% DM)
Potassium (K) is necessary for the function of all living cells. Potassium plays a key role in nerve transmission and muscle function. Potassium concentration in forages varies greatly and can range from 1.0% to 5.0%. The reason for large variations in forage potassium concentrations is due to forage plants being luxury consumers of soil potassium. In essence, forage potassium concentration is reflective of the soil potassium level on which the forage was grown. While often defined as low in potassium, forage grasses, including straw, may contain very high levels of potassium and lower potassium values observed in corn silage are due to dilution of the true forage potassium with grain. Potassium has practical nutritional implications in milk fever, heat abatement, hypomagnesimia and absorption of other cations such as Ca, Mg and P.

Sulfur (% DM)
Sulfur (S) is an essential element and a primary element in amino acids (methionine, cysteine). Sulfur in organic form is also present in the vitamins biotin and thiamine. Sulfur is an important part of many enzymes and antioxidant molecules. Most forages contain 0.20% sulfur and, in general, sulfur composition of forages has been reduced due to control of sulfur emissions from coal fired power plants. There are, however, situations when sulfur contents of ruminant diets needs to be monitored closely. Corn co-products such as corn gluten feed and distillers grains may contain very high levels of sulfur (>0.60%) and sulfur-related health disorders such as off-feed, low milk fat production or polioencephalmalcia may occur. In critical situations, NIRS or book values for S should not be used and wet chemistry values for sulfur should be obtained.

Lactic Acid (% DM)
Ideally, lactic acid should the most abundant acid produced during a fermentation. A lactic fermentation is the most efficient fermentation with 100% DM recovery and 96% energy recovery. Lactic acid does not inhibit fungal growth during spoilage, and so a balance of lactic with acetic is ideal. The smell of lactic acid is described as either the lack of a smell or a sweet, fresh smell. Inoculation with a homolactic inoculant, such as Crop-N-Rich MTD/1, can result in increases in lactic acid levels.

Acetic Acid (% DM)
Ideally, acetic acid, a volatile fatty acid, should be the second most abundant acid produced during fermentation. Acetic acid is a potent inhibitor of fungal growth and, therefore, minimizes spoilage. Thus, moderate levels in silages are beneficial. Too much acetic acid is detrimental because it can indicate loss of DM, a slow pH drop or inefficient fermentation, and it can depress intake. Thus, a lactic:acetic ratio of 3:1 is the ideal balance. Situations that may lead to excessive acetic acid are overly wet silages, silages that are not covered promptly, or ammoniated silages. An exception to this is silages where a more “controlled” acetic fermentation has occurred due to inoculation with Lactobacillus buchneri. Acetic acid is commonly associated with silages that smell like vinegar.

Butyric Acid (% DM)
Butyric acid is an undesirable fermentation acid. It indicates poor DM and energy recovery. It can make the feed unpalatable and it can even make animals sick if they are consuming more than 50 grams per animal daily. In general, butyric acid is seen in wet silages that have had a slow pH drop. Examples are wet alfalfa, rained-on crops, or silages at the bottom or sides of bunkers. If you suspect that a silo may go butyric, feed the silo as quickly as possible to stay ahead of butyric acid formation. It takes a couple months for butyric acid to form and, once it forms, it does not get better. If you have butyric silages, consider diluting them with non-butyric silages, airing the silages out to volatilize the acid, and avoid feeding these silages to prefresh or postfresh cows. Some laboratories report <0.01% butyric acid levels and this is the same thing as the silage having none. In some cases, NIR readings can report “false” butyric acid levels, so if your fermentation analysis reports butyric acid, and you think it is in error, talk to the laboratory about verification with wet chemistry methods.

Propionic Acid (% DM)
Propionic acid is usually low in silages. Propionic acid formation can result in a low DM recovery, but improvements in spoilage. Adding propionic acid as a silage preservative usually raises propionic acid levels up slightly (usually 0.15-0.30%). Propionic acid has a sharp, sweet smell. Low levels of propionic acid may be present in silages that are inoculated with Lactobacillus buchneri.

Lactic:Acetic Ratio
Lactic acid is beneficial because it reflects a high DM and energy recovery, but it does not improve aerobic stability. Acetic acid is beneficial because it improves aerobic stability, but it does not reflect a high DM and energy recovery. Therefore, a balance of these two acids is ideal, and the ideal ratio between lactic and acetic acid is 3:1. An exception to this is silages where a more “controlled” acetic fermentation has occurred due to inoculation with Lactobacillus buchneri. in this situation, the number will be slightly lower.

NFC (% DM)
Non-fiber carbohydrate (NFC) is a hetergenous mixture of carbohydrates, including starch, simple sugars, beta-glucans, galactans, and pectins. Non-fiber carbohydrates (NFC) is sometimes called nonstructural carbohydrate (NSC), although NFC and NSC are inherently different. NFC is calculated by difference [100-((%NDF - %ND-ICP)+ %CP + %Fat + Ash)]. NFC is primarily fermented to volatile fatty acids (VFAs) and rumen microbes use NFC to make microbial protein. Non-fiber carbohydrate is not a uniform nutrient and portions of NFC ferment faster than other portions. Due to differing carbohydrates within feed ingredient sources, NFC can ferment very differently, affecting milk production and rumen health differently. In some respects NFC is an older carbohydrate term as carbohydrates are frequently evaluated for starch and sugars (ethanol or water soluble carbohydrate). In many ways, knowing the starch and sugar concentration of a feed is as important as the NFC concentration because starch and sugars, while both NFC, ferment very differently.

TDN1X (%)
Total digestible nutrients (TDN) is the sum of the digestible fiber, protein, fat, and carbohydrate in a feed, forage or diet. TDN is calculated using summative equations and is converted to digestible energy (Mcals) in the net energy systems. TDN is still useful in comparing digestibility in diets that are primarily forage (heifer and dry cow diets). When moderate to high concentrations of concentrate or fat are fed to ruminants, net energy (NE) should be used to formulate diets and predict animal performance because TDN values tend to underpredict the energy supplied to the animal by concentrates and fat.

NEL, 3X (Mcals/cwt)
Net energy of lactation is frequently abbreviated differently (NEL, NEl, Nel or NEL) and is the amount of energy in a feed available to support milk production. Technically, a feed cannot have an NEL concentration as diets supply NEL and NEL supply is influenced by feed intake. Feed and forage testing laboratories calculate the NEL of a feed assuming an average dairy cow consuming 3 times her maintenance feed intake. As a result, NEL is commonly referenced as NEL-3X.

NEG (Mcals/cwt)
Net energy for maintenance (NEm) and gain (NEg) are actual caloric estimates (calories) of feeds. These energy values are more useful than TDN because they separate the amount of energy used for maintenance and gain purposes. NEm of a feed measures the calories supplied by the feed to meet the energy requirement for maintenance. NEg of a feed is the calories supplied to meet the energy needs for gain. NEm and NEg are commonly expressed as MCals/lb. 1 Mcal is 1,000 human calories (Kcal). Energy needs for maintenance are met first; thus, the NEm concentration of calories in a feed is used first. Once maintenance energy requirements are met, the remaining energy in the diet can go towards gain in which the NEg concentration of the feed is used. Feeds have two different NE composition values - one for maintenance and one for gain - because feed energy is used more efficiently for maintenance than for gain. Therefore, NEm values for a feed will always be higher than NEg values for a feed.

NEM (Mcals/cwt)
Net energy for maintenance (NEm) and gain (NEg) are actual caloric estimates (calories) of feeds. These energy values are more useful than TDN because they separate the amount of energy used for maintenance and gain purposes. NEm of a feed measures the calories supplied by the feed to meet the energy requirement for maintenance. NEg of a feed is the calories supplied to meet the energy needs for gain. NEm and NEg are commonly expressed as MCals/lb. 1 Mcal is 1,000 human calories (Kcal). Energy needs for maintenance are met first; thus, the NEm concentration of calories in a feed is used first. Once maintenance energy requirements are met, the remaining energy in the diet can go towards gain in which the NEg concentration of the feed is used. Feeds have two different NE composition values - one for maintenance and one for gain - because feed energy is used more efficiently for maintenance than for gain. Therefore, NEm values for a feed will always be higher than NEg values for a feed.

Milk/Ton (lb)
Milk per ton is an agronomy index used to rank overall forage quality within dairy production systems. Milk/ton is most commonly used in corn hybrid and legume-grass forage variety evaluations. Milk per ton values >3,500 lb/ton are considered exceptional. Milk per ton is not a nutrient and is therefore not used in ration balancing or diet formulation.

RFV
Relative feed value (RFV) is an index of forage quality. It is calculated using estimates of digestible dry matter (DDM) as calculated from ADF, and estimates the DM intake potential (as a percent of body weight, BW) as calculated from the NDF content of the forage. The RFV index is then calculated as DDM multiplied by dry matter intake (DMI as a percent of BW) divided by 1.29. RFV ranks forages relative to full bloom alfalfa, assuming full bloom alfalfa contains 41% ADF and 53% NDF. The RFV index for full bloom alfalfa is 100. High quality lactating dairy cow forages should have RFV indexes between 150 and 200. RFV is an older index of forage quality and has been replaced by RFQ (Relative Forage Quality), but RFV is still used in some applications because NDFD values are required to calculate RFQ and some laboratories do not have the ability to estimate NDFD.

RFQ
The Relative Forage Quality (RFQ) is an improvement of the RFV forage quality index because it better reflects actual animal performance. The RFQ index emphasizes NDF digestibility and, as such, does not discriminate against grasses because grass forages typically have a greater NDF content. The RFQ and RFV systems are on the same relative scale with values of 100 representing poor quality forages for lactating dairy cows. RFQ values of 150-200 would be considered high quality forages for lactating dairy cows. RFQ will be more dynamic than RFV because NDFD values will vary between forages. The equation for RFQ is RFQ = (DMI, % of BW) * (TDN, % of DM) / 1.23, where TDN is determined by summative equations and DMI is determined as DMI = 120/NDF + (NDFD – 45) * .374 / 1350 * 100.