THE REQUIRED FEED COMPOSITION FOR CATTLE AND SHEEP

In considering the necessary requirement of feed composition for cattle and sheep, some basic facts such as;

• The taking and utilization of actual feedstuff analysis whenever possible for ration formulation.
• The impossibility of determining feedstuff composition data, the next best source of information data is the tabulated data type.
• Since there is variability greatly in moisture content of feed, it is important to express feedstuff composition on a dry matter basis.

In the research of nutrition which is up to hundred years now, has made known the nutrients required by animals. Using this information, rations can be formulated from feeds and ingredients to meet these nutrient requirements. Animals which are fed by these formulated rations should not only remain healthy but be productive and more efficient.

The utmost point of feed analysis is to predict the productive response of animals when they are fed rations of a given composition. This is the main reason for information on feedstuff composition.

The table values for the composition of feedstuff

There are varieties in the composition of feedstuffs. In terms chemicals, that are "chemically pure" and therefore have a constant composition, feeds vary in their composition for some reasons. Actual analysis of a feed to be used in a ration is more accurate than tabular data. Obtain and utilize the actual analysis whenever possible and available.

However, it is either impossible to determine actual compositional data, or there is insufficient time to take analysis. Tabulated data forms are usually the next best source of information in the analysis. When adopting tabulated data format, remember that feeds vary in their composition. The organic constituents which are the crude protein, ether extract, crude fiber, acid detergent fiber and neutral detergent fiber can vary as much as 15 percent, the mineral constituents as much as 30 percent, as well as the energy values at least 10 percent, from table values.

This therefore means that the values shown can only be guides. For this reason they are called "typical values." they are not averages of published information. Some judgment used in arriving at some of the values in the hope that the values will be realistic for use in cattle and sheep rations.

In the formulation of feeds, they can be chemically analyzed for many things that may or may not be related to the response of the animals to which they are fed. The response of cattle and sheep when they are fed a feed is a beat similar, however, can be termed the biological response to the feed in question. This is a function of its chemical composition and the ability of the animal to derive useful nutrients from the feed.

At last it relates to the digestibility or availability of a nutrient in the feed for absorption into the body and its ultimate efficiency of use in the targeted animal. This also depends largely on the nutrient status of the animal and the productive or physiological function which is being performed by the animal. Ground fence posts and shelled corn may have the same gross energy value in a bomb calorimeter, but have markedly different useful energy value when consumed by the animal.

This states that the biological attributes of a feed have much greater meaning in predicting the productive response of the animals. However, they are more difficult to accurately determine due to the fact that there is an interaction between the chemical composition of the feed and the digestive and metabolic capabilities of the animals which are being fed.

The use of information contained in the formulation table

Names of feeds which are use

The most obvious or the commonly used feed names are Alfalfa cubes, Alfalfa hay, Alfalfa silage, Ammonium sulfate, Barley silage, Barley straw, Barley grain, Blood meal, Bone meal, Brewers dried grain and so on. Feeds designated as "fresh" are feeds that are grazed or fed as fresh cut materials.

Dry Matter

The moisture content of feeds can vary greatly. Thus dry matter content can be the biggest main reason for variation in the composition of feedstuffs on an "as fed basis." For this major reason, the composition of chemical constituents and biological attributes of feeds are shown on a dry matter basis. Due to the fact that dry matter can vary greatly, and because one of the factors regulating total feed intake is the dry matter content of feeds, ration formulation on a dry matter basis is sounder than using as fed basis. To transform the values shown to an as fed basis, multiply the decimal equivalent of the dry matter content times the compositional value which could be derived from your formulated table.

Protein

Crude protein value for each feed must always be known in the formulated table. Crude protein is determined by the taking of nitrogen times 6.25. Proteins contain 16 percent nitrogen on the average. In the formulation, Crude protein does not give any information on the actual protein and non-protein content of a feed. Digestible protein has been included in many feed composition tables, but due to the fact that the large contribution of body protein to the apparent protein in the feces, digestible protein is more misleading than Crude Protein. Calculate digestible protein from the Crude Protein content of the ration fed to cattle or sheep by the following equation: % DP = 0.9 (% CP) - 3, where % DP and % CP are the ration values on a dry matter basis.

Rumen by-pass protein, or under graded intake protein, represents the percent of protein that passes through the rumen without being degraded by rumen microorganisms. Like other biological attributes, these values are not constant. By-pass values for many feeds have not been determined. Reasonable estimates are difficult to establish.

The degradable intake protein is used to meet the nitrogen requirements of rumen micro-organisms. Nitrogen sources such as urea are the most economical sources of degradable intake protein. Balancing degradable intake protein and under graded intake protein sources provides a more accurate way of meeting the metabolized protein needs of ruminants.

The crude, acid detergent and neutral detergent fibers

Crude fiber is declining in popularity as a measure of low digestible material in feeds. The major problem with crude fiber is the variable amounts of lignin, which is not digestible, are removed from various feeds in the crude fiber procedure. In the old scheme, the material removed was called nitrogen-free extract and was thought to be more digestible than crude fiber, even though many feeds have been shown to have a higher digestibility for crude fiber than nitrogen free extract. One major reason crude fiber remained in the analytical scheme for feedstuff analysis was its requirement for the determination of neutral detergent fiber.

There are newer procedures which have developed an alternate analytical scheme, namely, acid detergent fiber and neutral detergent fiber. Acid detergent fiber is highly related to digestibility in the animal. Neutral detergent fiber is related to voluntary intake of the feed and the availability of net energy from digestible energy. Both measures relate more directly to predicted animal performance, so they are more valuable than crude fiber. Also, if total digestable nutrients are replaced by other measures of energy value, there will be little use of the crude fiber content of feeds. As more complete data on the acid detergent fiber and neutral detergent fiber content of feeds are developed, crude protein will be reduced.

Minerals

Calcium and phosphorus are the major important minerals in most feeding situations. Potassium becomes important as the level of concentrate increases in the ration, or when non-protein nitrogen is substituted for intact protein. Sulfur also becomes more important as the level of non-protein nitrogen increases in the ration that is been formulated.

Vitamins

Only vitamin A is of general practical importance in cattle and sheep feeding. The vitamin A and carotene in feeds depend largely on maturity and conditions at harvest and the length and conditions of storage. Therefore, it is probably wrong to rely entirely on harvested feeds as a source of vitamin A. Where roughages are being fed that contain good green color or are being fed as immature fresh forages such as pasture, there will probably be sufficient vitamin A.

Energy 

Total digestible nutrients should be considered in feed formulation due to the fact that there are more total digestible nutrients values for feeds, and because this has become a standard system for expressing the energy value of feeds for cattle and sheep. There are several technical problems which are associated with total digestible nutrients. However, there is a poor relationship between crude fiber and nitrogen free extract digestibility in certain feeds. Total digestible nutrients also overestimate the value of roughages compared to concentrates in producing animals. Some have argued that energy is not measured in pounds or percent, so total digestible nutrients are not a valid measure of energy.

Digestible energy

Several feed studies have shown that there is a constant relationship between total digestible nutrients and digestible energy; there are 2 Mcals of digestible energy per pound of total digestible nutrients. However, digestible energy can be calculated by multiplying .02 times the percent total digestible nutrients content. Because digestible energy is measured in calories, it is technically preferred over total digestible nutrients.