The average of the two NE values can be used, but this would be true only for cattle and sheep eating twice their maintenance energy requirement. The most accurate way to use these NE values to formulate diets is to use the NE_m value plus a multiplier times the NE_g value, all divided by one plus the multiplier. The multiplier is the level of feed intake relative to maintenance.

For example, if 700-lb. cattle are expected to eat 18 lbs. of DM, 8 lbs. of which will be required for maintenance, the diet's NE value would be:

NE = [NE_m + (10/8)(NE_g)]/[1 + (10/8)].

In deciding on the energy system to use, there's no question on NE's theoretical superiority over TDN in predicting animal performance. But this superiority is lost if only NE_g is used to formulate diets. If NE is used, some combination of NE_m and NE_g is best.

NE₁ values are also shown but few have actually been determined. NE₁ values are similar to NE_m values except for very high- and low-energy feeds.

Protein: Crude protein (CP) values are shown for each feed, which are Kjeldahl nitrogen times 100/16 or 6.25, since proteins contain 16% nitrogen on the average. CP provides no information on the actual protein and non-protein nitrogen (NPN) content of a feed.

Digestible protein (DP) has been included in many feed composition tables. 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 passing through the rumen without degradation by rumen microorganisms. Degradable intake protein (DIP) is the percent of CP degraded in the rumen and is equal to 100 minus UIP. Like other biological attributes, these values aren't constant. UIP values on many feeds haven't been determined, and reasonable estimates are difficult to make.

How should these values be used to improve the predictability of animal performance when fed various feeds? Generally, DIP can supply CP up to 7% of the diet. If the required CP 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 UIP.

Once the relationships between UIP and DIP have been better quantified, CP requirements may be lowered, especially at higher CP levels. For diets high in rumen fermentable carbohydrate, DIP requirements may determine the total CP required in the diet.

Crude, acid detergent and neutral detergent fiber: Crude fiber (CF) is declining in use as a measure of poorly digested carbohydrates in feeds. Its major problem is that variable amounts of lignin, which isn't digestible, are removed in the CF procedure. In the old scheme, the remaining carbohydrates (NFE) were thought to be more digestible than CF despite many feeds having higher CF digestibility than NFE. One reason CF remained in the analytical scheme was its apparent requirement for the TDN calculation.

Improved analytical procedures for fiber have been developed, namely acid detergent fiber (ADF) and neutral detergent fiber (NDF). ADF is related to feed digestibility and NDF is somewhat related to voluntary intake and the availability of net energy. Both measures relate more directly to predicted animal performance and thus are more valuable than CF. Lignification of NDF, however, alters the availability of the surface area to fiber-digesting rumen microorganisms; lignin, therefore, may be added to future tables.

Recently, effective NDF (eNDF) has been used to better describe the dietary fiber function in high-concentrate, feedlot-type diets. While eNDF is defined as the percent of NDF 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. Thus, when formulating high-concentrate diets, including eNDF may help prevent acidosis in the rumen. In feedlot diets, the recommended eNDF levels range from 5-20% depending on bunk management, inclusion of ionophores, digestion of NDF and/or microbial protein synthesis in the rumen.

Estimated eNDF values are shown for many feeds. These should be decreased depending on degree of feed processing (e.g., chopping, grinding, pelleting, flaking) 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 feed's crude fat content.

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

Sulfur (S) also becomes more important as the NPN level increases in the diet. High dietary S levels compounded by high S levels in drinking water, however, can be detrimental. Zinc (Zn) is shown because it's less variable and 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.

The level of many other trace minerals in feeds is largely determined by the level in the soil on which the feeds are grown or other environmental factors that preclude showing a single value. Iodine and selenium are required nutrients that may be deficient in many diets, yet their level in a feed is more related to the conditions under which the feed is grown than to a characteristic of the feed itself. Trace mineralized salt and trace mineral premixes are generally used to supplement trace minerals; their use is encouraged where deficiencies exist.

Vitamins: Vitamins are not included in 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. This depends largely on maturity and conditions at harvest, and the length and conditions during storage. Thus, it's probably unwise to rely entirely on harvested feeds as a source of vitamin A value.

Where roughages are fed that contain good green color or are being fed as immature, fresh forages (e.g., pasture), there will probably be sufficient vitamin A value to meet animal requirements. Other vitamins, if required, should be supplied as supplements.