Accompanying this discussion is a table showing the typical composition of feedstuffs and ingredients commonly used in the feeding of cattle and sheep in North America. Nutrition research spanning more than 100 years has defined the nutrients required by animals. Using this information, diets can be formulated from feedstuffs and ingredients to meet these requirements with the exception that animals will not only remain healthy but will also be productive and efficient.

Composition Values

Unlike chemicals, which are “chemically pure” and therefore have a constant composition, feeds vary in their composition. Actual analysis of a feed is much more accurate than the use of tabulated composition data. While actual analysis should be obtained and used when possible it's often either impossible to determine actual composition or there is insufficient time to obtain such analysis. Tabulated data are the next best source of information.

In using tabulated data, remember that feeds vary in their composition. Using the data shown in the accompanying table, you can expect the organic constituents (e.g., crude protein, ether extract, crude fiber, acid detergent fiber and neutral detergent fiber) to vary as much as ±15%, the mineral constituents to vary as much as ±30% and the energy values to vary up to ±10%. Therefore, values shown can only be guides. For this reason they are called “typical values.” They are not averages since judgment was used in arriving at some of the values in the hope these values will be realistic for use in formulating cattle and sheep diets.

New crop varieties usually result in nutrient composition changes. Genetically modified crops will result in feeds with generally improved nutrient content and availability and/or decreased anti-nutrient factors.

Chemical Constituents vs. Biological Attributes

Feeds can be chemically analyzed for many things that may or may not be related to the response of an animal when fed the feed. The accompanying table shows certain chemical constituents. The response of cattle and sheep when fed a feed, however, can be termed the biological response to the feed that is a function of its chemical composition and the ability of the animal to derive useful nutrient value from the feed.

The latter relates to the digestibility or availability of a nutrient in the feed for absorption into the body and its ultimate efficiency of use depending upon the nutrient status of the animal and the productive or physiological function being performed by the animal. Ground fence posts and shelled corn may have the same gross energy value but have markedly different useful energy value (TDN or EN) when consumed by the animal.

Biological attributes of a feed have much greater meaning in predicting the productive response of animals but are more difficult and costly to accurately determine. This is due to interaction between the chemical composition of a feed with the digestive and metabolic capabilities of the animal being fed. They are more variable than chemical constituents but are generally more predictive, however, since they relate to the response of an animal being fed the feed or diet.

Source Of Information

Several sources of information were used in arriving at the typical values shown in the table. Where information was not available, a reasonable estimate made from similar feeds or stage of maturity has been used. Where zeros appear, the amount is so small that it can be considered insignificant in practical diet formulation; blanks indicate that the value is unknown.

Using The Table Information

Feed names: Obvious or commonly used feed names are used. Feeds designated as “fresh” are feeds that are grazed or fed as fresh-cut materials.

Dry matter: Typical dry matter (DM) values are shown; however, the moisture content of feeds can vary greatly. Therefore, DM content can be the biggest reason for variation in feedstuff composition on an “as-fed basis.” Chemical constituents and biological attributes of feeds shown in the table are on a DM basis.

DM can vary greatly and because one of the factors regulating total feed intake is the DM content of feeds, diet formulation on a DM basis is sounder than using as-fed basis. To convert a value to an as-fed basis, multiply the decimal equivalent of the DM content by the compositional value shown in the table.

Energy: Four measures of the energy value of feeds are shown. TDN is shown because there are more determined TDN values for feeds and it has been the standard system for expressing the energy value of feeds for cattle and sheep. There are several technical problems with TDN, however. The digestibility of crude fiber (CF) may be higher than for nitrogen-free extract (NFE) in certain feeds. TDN overestimates the value of roughages compared to concentrates in producing animals.

Some have argued that energy is not measured in pounds or percent and therefore TDN is not a valid measure of energy. However, this is more a scientific argument than a criticism of the predictive value of TDN.

Digestible Energy: Digestible Energy (DE) values are not included in the table. There is a constant relationship between TDN and DE in cattle and sheep; DE (Mcal/cwt.) can be calculated by multiplying the %TDN content by two.

Protein: Crude protein (CP) values are shown for each feed, which are Kjeldahl nitrogen times 100/16 or 6.25, because proteins contain 16% nitrogen on the average. Crude protein does not give any information on the actual protein and non-protein nitrogen content of a feed.

Digestible protein (DP) has been included in many tables of feed composition but because of the contribution of microbial and body protein to the protein in feces, DP is more misleading than CP. One can estimate DP from the CP content of the diet fed to cattle or sheep by the following equation: %DP = 0.9(%CP) -3 (where %DP and %CP are the diet values on a DM basis.)

Undegradable intake protein (UIP; rumen “by-pass” or escape protein) values represent the percent of CP that passes through the rumen without being degraded by the rumen microorganisms. Like other biological attributes, these values are not constant.

UIP values on many feeds have not been determined and reasonable estimates are difficult to make. Generally, degradable intake protein (DIP) can supply CP up to 7% of the diet. If the CP required in the diet exceeds 7% of the DM, all CP above this amount should be UIP. In other words, if the final diet is to contain 13% CP, 6 of the 13 percentage units, or 46% of the CP, should be in the form of UIP. Once the relationships between UIP and DIP have been better quantified, CP requirements may be lowered especially at higher CP levels.

Crude, acid detergent and neutral detergent fiber: Crude fiber (CF) is declining in popularity as a measure of poorly digestible carbohydrates in feeds. Improved analytical procedures for fiber have been developed, namely acid detergent fiber (ADF) and neutral detergent fiber (NDF). ADF is related to digestibility and NDF is somewhat related to voluntary intake and the availability of net energy. One reason CF remained in the analytical scheme was its apparent requirement for the calculation of TDN.

Recently, effective NDF (eNDF) has been proposed to better describe the dietary fiber function in high concentrate, feedlot-type diets. While eNDF is defined as the percent of NDF that is retained on a screen similar in size to particles that will pass from the rumen, this value is further modified based on feed density and degree of hydration.

Rumen pH is correlated with dietary eNDF when diets contain less than 26% eNDF. When formulating high concentrate diets, including a recommended 5-20% eNDF will help to prevent acidosis in the rumen. Estimated eNDF values shown for many feeds must be modified depending on degree of feed processing (eg., chopping, grinding, pelleting) and hydration (fresh forage, silages, high-moisture grains) if these feed forms are not specified in the table.

Ether extract: Ether extract (EE) shows the crude fat content of the feed.

Minerals: Values are shown for only certain minerals. Calcium (Ca) and phosphorus (P) are important minerals to consider in most feeding situations. Potassium (K) becomes more important as the level of concentrate increases and when non-protein nitrogen is substituted for intact protein in the diet.

Sulfur (S) also becomes more important as the level of non-protein nitrogen increases in the diet.

Zinc (Zn) is shown because it is less variable and is more generally near a deficient level in cattle and sheep diets.

Chlorine (Cl) is of increasing interest for its role in dietary acid-base relationships.

Vitamins: Vitamins have been omitted from the table. The only vitamin of general practical importance in cattle and sheep feeding is the vitamin A value (vitamin A and carotene) in feeds that depends largely on maturity and conditions at harvest, and the length and conditions of storage.

It is probably unwise to rely entirely on harvested feeds as a source of vitamin A value. Roughages that contain good green color or are being fed as immature fresh forages (e.g. pasture), probably contain sufficient vitamin A value to meet the animal's requirement. Other required vitamins should be supplied as supplements.

Future Revisions

I welcome suggestions and compositional data to this table. When sending compositional data, please adequately describe the feed, indicate the dry matter or moisture content and whether analytical values are given on an as-fed or DM basis. If more than one sample of a feedstuff was analyzed, the number of samples should be indicated.

R.L. Preston, emeritus professor from Texas Tech University can be reached at 191 Columbia Court, Pagosa Springs, CO 81147-7650, rlpreston@centurytel.com

(All values except dry matter are shown on a dry matter basis)

ENERGY PROTEIN FIBER
FEEDSTUFF DM TDN NEM NEG NEL CP BYPASS CF ADF NDF eNDF EE ASH CA P K CL S ZN
% % Mcal/cwt. % % % % % % % % % % % % % ppm
Alfalfa Cubes 91 57 57 25 57 18 30 29 36 46 40 2.0 11 1.30 0.23 1.9 0.37 0.35 20
Alfalfa Dehydrated 17% CP 92 61 62 31 61 19 60 26 34 45 6 3.0 11 1.42 0.25 2.5 0.45 0.24 21
Alfalfa Fresh 24 61 62 31 61 19 18 27 34 46 41 3.0 9 1.35 0.27 2.6 0.40 0.28 18
Alfalfa Hay Early Bloom 90 59 59 28 59 19 20 28 35 45 92 2.5 8 1.41 0.26 2.5 0.38 0.27 22
Alfalfa Hay Full Bloom 88 54 54 20 54 16 25 34 40 52 92 2.0 8 1.20 0.23 1.7 0.37 0.23 23
Alfalfa Hay Mature 88 50 50 12 49 13 30 38 45 59 92 1.3 8 1.18 0.19 1.5 0.35 0.20 23
Alfalfa Hay Midbloom 89 58 58 26 58 17 23 30 36 47 92 2.3 9 1.40 0.24 2.0 0.38 0.26 24
Alfalfa Leaf Meal 89 69 71 43 70 28 15 15 25 34 35 2.7 15 2.88 0.34 2.2 0.32 39
Alfalfa Seed Screenings 91 84 92 61 87 34 13 15 10.5 6 0.30 0.67
Alfalfa Silage 30 55 55 21 55 18 19 28 37 49 82 3.0 9 1.40 0.29 2.6 0.41 0.29 26
Alfalfa Silage Wilted 39 58 58 26 58 18 22 28 37 49 82 3.0 9 1.40 0.29 2.6 0.41 0.29 26
Alfalfa Stems 89 47 47 7 46 11 44 44 51 68 100 1.3 6 0.90 0.18 2.5
Almond Hulls 89 59 59 28 59 5 60 16 27 35 100 3.3 7 0.25 0.10 2.0 0.03 0.07 20
Ammonium Chloride 99 0 0 0 0 163 0 0 0 0 0 0.0 0.00 0.00 0.0 66.00 0.00 0
Ammonium Sulfate 99 0 0 0 0 132 0 0 0 0 0 0.0 24.15
Apple Pomace Dried 89 65 66 37 66 5 15 19 35 45 34 5.2 4 0.13 0.12 0.5 0.02
Apple Pomace Wet 20 68 70 41 69 6 10 17 34 40 34 5.6 4 0.14 0.14 0.6 0.06 11
Artichoke Tops (Jerusalem) 27 61 62 31 61 6 18 30 41 40 1.1 10 1.62 0.11 1.4
Avocado Seed Meal 91 52 52 16 51 20 19 24 1.2 16
Bahiagrass Hay 90 51 51 14 50 8 37 32 41 72 98 1.9 8 0.48 0.20 1.4 0.21
Bakery Product Dried 90 90 100 68 94 12 30 4 6 14 0 11.0 4 0.18 0.28 0.3 2.25 0.15 33
Barley Feed Pearl Byproduct 90 73 77 48 75 15 12 15 3.9 5 0.05 0.45 0.7 0.06
Barley Grain 89 84 92 61 87 12 28 5 7 19 34 2.1 3 0.06 0.38 0.6 0.18 0.16 23
Barley Grain 2-row 87 84 92 61 87 12 6 8 24 34 2.3 2 0.05 0.31 0.6 0.18 0.17
Barley Grain 6-row 87 84 92 61 87 11 6 8 24 34 2.2 3 0.05 0.36 0.6 0.18 0.15
Barley Hay 90 57 57 25 57 9 28 37 65 98 2.1 8 0.30 0.28 1.6 0.19 25
Barley Grain Screenings 89 77 82 53 79 12 9 11 2.6 4 0.30 0.33 0.7 0.15
Barley Grain Steam Flaked 85 90 100 70 100 12 39 5 7 19 30 2.1 3 0.06 0.35 0.6 0.18 0.16 23.00
Barley Grain Steam Rolled 86 84 92 61 87 12 38 5 7 19 27 2.1 3 0.06 0.41 0.6 0.18 0.17 30
Barley Grain Lt. Wt. (42-44 lb./bu.) 88 78 83 54 80 13 30 9 12 30 34 2.3 4
Barley Silage 35 59 58 26 58 12 22 34 37 58 61 3.0 9 0.46 0.30 2.4 0.22 28
Barley Silage Mature 35 58 58 26 58 12 25 30 34 50 61 3.5 9 0.30 0.20 1.5 0.15 25
Barley Straw 90 43 44 0 42 4 70 42 52 78 100 1.9 7 0.33 0.08 2.1 0.67 0.16 7
Beans Navy Cull 90 84 92 61 87 24 25 5 8 20 0 1.4 5 0.15 0.59 1.4 0.06 0.26 45
Beet Pulp Dried 91 75 79 50 77 11 44 21 21 41 33 0.7 6 0.65 0.08 1.4 0.40 0.22 22
Beet Pulp Dried With Molasses 92 76 81 52 78 11 34 17 22 40 33 0.6 6 0.60 0.10 1.8 0.42 11
Beet Pulp Wet 17 76 81 52 78 11 35 20 23 48 33 0.7 6 0.68 0.08 1.4 0.40 0.21 20
Beet Pulp Wet With Molasses 24 77 82 53 79 11 25 16 21 39 33 0.6 6 0.60 0.10 1.8 0.42 11
Beet Top Silage 25 52 52 16 51 12 12 2.0 32 1.38 0.22 5.7 0.57 20
Beet Tops (Sugar) 20 58 58 26 58 14 10 14 25 41 1.5 24 1.20 0.23 5.1 0.20 0.45 20
Bermuda Grass Coastal Dehydrated 90 62 63 33 63 16 40 26 29 40 10 3.8 7 0.40 0.25 1.8 0.23 18
Bermuda Grass Coastal Hay 89 56 56 23 56 10 20 30 36 73 98 2.1 6 0.47 0.21 1.5 0.22 16
Bermuda Grass Hay 89 53 53 18 53 10 18 30 39 78 98 1.9 8 0.46 0.20 1.5 0.25 33
Bermuda Grass Silage 26 50 50 12 49 10 15 30 37 77 48 1.9 8 0.46 0.20 1.5 0.25 33
Birds-Foot Trefoil Fresh 22 66 68 38 67 21 20 21 31 47 41 4.4 9 1.78 0.25 2.6 0.25 31
Birds-Foot Trefoil Hay 89 57 57 25 57 16 22 31 38 50 92 2.2 8 1.73 0.24 1.8 0.25 28
Biuret 99 0 0 0 0 248 0 0 0 0 0 0.0 0 0.00 0.00 0.0 0.00 0.00 0
Blood Meal 91 66 68 38 67 92 80 1 2 10 0 1.4 3 0.32 0.28 0.2 0.30 0.70 22
Bluegrass KY Fresh Early Bloom 36 69 71 43 70 15 20 27 32 60 41 3.9 7 0.37 0.30 1.9 0.42 0.19 25
Bluegrass Straw 93 45 45 3 44 6 40 50 78 90 1.1 6 0.20 0.10
Bluestem Fresh Mature 61 50 50 12 49 6 34 2.5 5 0.40 0.12 0.8 0.05 28
Bone Meal Steamed 95 16 27 0 11 13 1 0 0 0 11.6 77 27.00 12.