What Is Crude Protein In Animal Feed
The term rough protein is still often used in nutrition formulation. Merely some may question whether this is still up to date. Later all, it is all about the amino acids, not crude protein content.
The definition of crude protein, which quantifies every bit the amount of analysed nitrogen multiplied by a factor of vi.25, goes back to the 19th century. In the 1860s, Henneberg and Stohmann attempted to suspension down feed composition into various groups of substances for belittling purposes. Rough poly peptide was defined by the nitrogen-containing fraction, whereby the boilerplate nitrogen content was assumed to be 16% (resulting in a factor of 6.25). These groups of rough nutrients, which include water, crude protein, rough lipid, crude fiber, nitrogen-complimentary extracts (NFEs), and ash, all add up to 100%.
While the Weende Analysis, every bit this method is called, has been modified, particularly with respect to greater differentiation within the carbohydrate fraction (encounter for instance van Soest et al., 1991), the N fraction continues to be used as a mensurate of crude protein to this 24-hour interval. The amount of crude poly peptide that an animal consumes, in other words, is considered an indication of its food intake. Nutritionists have to deal with rough protein on a regular basis. Sometimes, certain countries even require a minimum of crude poly peptide in the beast feed conception. Also certain labeling regulations for feed blends require that it must exist indicated as a mandatory analytical parameter. But does this view on crude protein still make sense today?
Different nitrogen-containing components
Firstly, we need to bespeak out that amino acids, which actually make upward poly peptide, are not the merely nitrogen-containing components of the feed. Others include nucleic acids and nucleotides, which come from our genetic material in the form of DNA and RNA and which are present in all plant and animal cells. This fraction alone accounts for some 20% of what is known equally non-poly peptide nitrogen (NPN). Vitamins, amines, amides, urea, and other substances play a role here as well. The NPN fraction makes upwards some ten% of rough protein.
A misleading term?
Originally, an amino acrid profile was assumed leading to the factor of vi.25 (16% N); a factor that is in fact variable, of course, and that depends on the amino acid contour and on the size of the NPN fraction. In the real world of fauna nutrition, we rarely see feeds that correspond to a factor of half-dozen.25, which merely represents a weighted average of the feed ingredients. We may conclude, every bit a consequence, that the term "crude poly peptide" is rather misleading. In fact, the Weende Assay does not involve analysing every crude nutrient: NFE is a calculated residuum parameter, and if the N content of a protein deviates from the assumption of sixteen%, not only will the crude protein content incorporate an error but the calculated value for NFE and/or balance organic thing (van Soest method, etc.) will equally well. If the estimated crude protein content is too high, the estimated NFE/balance organic matter content will automatically be too low. If for no other reason than this, nosotros should dispense with the crude poly peptide parameter, despite the fact that knowing the N content is important and even necessary.
Not indication of nutritional value
A far more important business concern, however, is that crude protein does not provide whatever indication whatsoever of the nutritional value of a poly peptide, making it utterly unsuitable for use equally a nutrient. The nutritional value of a protein instead depends on the limerick of the amino acids it contains. Monogastric animals (and humans), afterward all, require amino acids and non crude protein.
Figure ane – Comparing between feed containing low levels of raw protein and a balanced amino acid profile.
Moreover, the quantitative and qualitative composition of amino acids must be considered in light of the requirements of the creature species, its stage of development, and its gender (and, in ideal case, other criteria). Studies on protein reduction and on amino acid dose responses offer striking confirmation of this correlation (Effigy ane). Taking as the starting indicate a relatively unbalanced feed containing a great bargain of crude protein, researchers achieved the same performance in broilers using a feed containing low levels of raw poly peptide and a balanced amino acid profile (Figure ane). A deficit in one essential amino acid prevents protein synthesis from completing. Synthesis is instead interrupted, which leads to reduced growth performance (or, in the instance of laying hens, reduced daily egg mass). Adding the missing amino acid to this feed has only a marginal effect on the crude protein content but an enormous impact on animal output and efficiency every bit demonstrated in Figure two. In this instance, the highest inclusion level of DL-Methionine (0.24%) contributed but 0.14% rough protein.
Figure 2 – Upshot of adding the missing amino acid to rough protein content, animal output and efficiency.
Turn to essential amino acids
In other words, when lawmakers stipulate that compound feed for individual animal species shall contain a minimum level of rough protein, they are not in any way ensuring that the animals will obtain the amino acids they need in the quantities they need. In addition, requirements such equally these prevent intelligent reductions in nitrogen content while maintaining an platonic amino acid composition. The latter not merely has an enormous leveraging upshot on N emissions in animal husbandry, it also impacts animate being health. As a rule of thumb, lowering the N content in feeds by only one percentage point with the corresponding application of the ideal protein concept reduces Northward-excretions by 10%. It follows that we need to move abroad from the crude protein concept and would be better turning our attending to (essential) amino acids, a change that no longer poses whatever problem in analytical terms. Nutrition scientific discipline journals and books could lead the way by reporting N content in conjunction with the amino acid limerick rather than rough protein.
In terms of nutritional value, nevertheless, considering just the analysed amino acid content is nonetheless containing a source of error. It is sufficiently well known that animals cannot digest all individual ingredients of chemical compound feed equally well, which means that different feeds vary in terms of overall digestibility (Tabular array ane). In other words, feeds in which, say, the total methionine+cysteine content is identical may vary in terms of their nutritional value because one feed is more readily digested than the other, making more than methionine+cysteine bachelor to the animal. The challenge here, however, is that usually the content of digestible amino acids can be calculated but non directly analysed in a compound feed. Nevertheless, formulating feeds on the ground of digestible amino acids results in feeds that more precisely come across animals' requirements. Requirements in terms of digestible amino acids are rather well known.
Analytical process
Another cistron to consider has to do with the chemical analysis of amino acids and how those are indicated in certificates of analysis. The analytical procedure involves hydrolyzing proteins to suspension them down into their individual amino acids, which are then quantified and reported as consummate, private amino acids. Prior to analysis, withal, vast majority of all amino acids are actually linked to each other via peptide bonds in proteins. This in fact means that one molecule of water (H2O) is missing for every amino acid in the protein, and that has implications for quantification. All of the amino acids in soybean meal excerpt (including tyrosine, and accounting for the deviation both between glutamine and glutamic acid and between asparagine and aspartic acid) would add up to 46.iii% (Table 2), for example. If corrected for HtwoO, even so, that value is only 39.9%. It is like shooting fish in a barrel to guess to which nutrient fraction the divergence of six per centum points needs to be added to. That is to the analytical balance value (NfE, residual organic thing). Correcting for this lack of precision does not require analytical changes of any kind, every bit it tin easily be derived mathematically.
Replacement of definition
In summary, crude poly peptide is a meaningless parameter from the viewpoint of both nutritional physiology and the concept of precise livestock farming. The term is even misleading, considering it contains quantitative errors that take implications in calculations for other nutrient fractions. In improver, rough protein does not reflect the quality of a protein (i.e., its amino acid content and digestibility), making data on crude protein content of little value. Equally such, we should avoid using the term crude protein, at all-time replacing it with information on nitrogen content along with a corresponding amino acid profile. Moreover, one should also consequently signal amino acids in terms of digestible amino acids. One farther point that could make fauna feed evaluation and brute diet, respectively, more precise would be to correct the analytical amino acrid content for the amount of water present, which, like to crude poly peptide content, results in substantial errors in calculated balance parameters (such equally NFE, rest organic affair, etc.) when evaluating feeds.
Source: https://www.allaboutfeed.net/animal-feed/feed-additives/do-we-still-need-to-work-with-crude-protein/
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