Dietary protein quality

The amino acid scoring pattern proposed by FAO/WHO/UNU [110] for children of preschool age should be used to evaluate dietary protein quality for all age groups except infants. 

Nitrogen losses per unit of nitrogen deposition as derived from modelling of protein utUization depending on dietary protein quality parameters and age of growing barrows... 

Relating NEX ND from both of the equations, the relationship between N1 and NEX ND ratio dependent on dietary protein quality is given in Figure 1. 

N-maintenance requirement (mg/B Wj g ) b is the slope of the N-retention curve (protein quality parameter, independent of NI), and e is the basic number of the natural logarithm (In). Dietary protein quality (b) and Met-efficiency (bc ) data were derived according to earlier apphcations of the procedure (Samadi and Lieberf 2008 Wecke andLieberf 2010). Met-requirements depending on aimed growth response and realized dietary Met-efficiency were derived according to the equation ... 

Table 2 provides the observed relative changes of model parameters for dietary protein quality (b) and AA-efificiency (be" ), when setting the results with control diet as a standard (=100). 

Tyagi SR, Singh Y, Sriram K, et al. 1985. Quality and quantity of dietary protein and acute endosulfan metabolic toxicity in rat liver microsomes. Indian J Med Res 81 480-487. 

Since this increased calcium loss, the quality of dietary protein may be important in conserving body calcium in the bone reservoir via the kidney. Human renal studies have corroborated animal data in-so-far as calcium excretion as influenced by urinary acidity is concerned. This was emphasized by Marone et al. (15) who reported increased excretion of calcium in the acidotic dog and by Zemel, et al. (27) who studied calcium filtration by the kidney. They fed subjects low or high-protein (50 or 150 g/d) diets, then compared... 

Relative quality of some common dietary proteins. 

Dietary protein provides essential amino acids. The quality of a protein is a measure of its ability to provide the essential amino acids required for tissue maintenance. Proteins from animal sources, in general, have a higher quality protein than that derived from plants. However, proteins from different plant sources may be combined in such a way that the result is equivalent in nutritional value to animal protein. 

The nutritional quality of dietary protein depends largely on the pat-... 

Determining protein quality analysis is important in food science, particularly for developing foods with targeted nutritional value, and in animal feeding and husbandry. Protein is the key component in the diet of any farmed species, particularly in aquaculture and the pet food industry, making an accurate assessment of protein utilization critically important. Protein quality analysis provides an estimate of the content and bioavailability of indispensable or dietary essential amino acids. 

A number of procedures used to determine protein quality involve bioassays. Bioassays require feeding live animals protein ingredients for a specified period of time, and then estimating the nutritive value of the protein. Two such assays are the rat-based protein efficiency ratio (PER) bioassay and the human nitrogen balance assay (Dimes et al., 1994). Animal feeding experiments require chemical analyses of both the dietary inputs and then the metabolic output of the animal (e.g., body composition analysis, fecal sample analysis, collection, and assay for urine) from which the efficiency of protein metabolism can be predicted as well as how the protein supports animal growth and cell maintenance. 

Cereal grains, such as maize, barley, wheat and sorghum, are the main ingredients of poultry diets and usually provide 30-60% of the total AA requirements. Other sources of protein such as soybean meal and canola meal must be provided to ensure adequate amounts and a proper balance of essential AAs. The protein levels necessary to provide adequate intakes of essential AAs will depend on the feedstuffs used. Feedstuffs that contain high-quality proteins (i.e. with an AA pattern similar to the bird s needs) or mixtures of feedstuffs in which the AA pattern of one complements the pattern in another will meet the essential AA requirements at lower dietary protein levels than feedstuffs with a less desirable AA pattern. This is important if one of the goals is to minimize N excretion. 

Bowen, S. H., Lutz, E. V., and Ahlgren, M. O, Dietary protein and energy as determinants of food quality trophic strategies compared, Ecology, 76, 899, 1995. 

Felton, G.W., Donato, K.K., Broadway, R.M., and Duffey, S.S., Impact of oxidized plant phenolics on the nutritional quality of dietary protein to anoctuid herbivore, Spodoptera exigua, J. Insect Physiol., 38, 277, 1992. 

Tt is well recognized that the nutritional value of dietary proteins de-pends primarily on the content of their constituent amino acids, especially of their essential amino acids. Because of deficiencies of lysine and methionine, and to a lesser extent of a few other amino acids, proteins from plants and other alternative sources have low biological quality. Moreover, incomplete digestion of the protein also may result in a lack of complete availability (I) of the essential amino acids and may further reduce its value. In many raw plant foodstuffs such as soybeans, common beans, or unprocessed protein foods, undenatured... 

Because of the change in level of dietary protein, it is not possible to positively determine whether quality of protein or level... 

The quality of different proteins can be expressed according to their chemical score, protein efficiency ratio (PER), biological value (BV), and net protein utilization (NPU). These parameters refer to the different tests used to define the protein s quality. The chemical score refers only to the property of the protein in question. The PER, BV, and NPU refer to relationship.s between the dietary protein and the consumer. The values of the PER, BV, and NPU depend on properties of both the protein in question and the needs of the animal. The chemical score, PER, BV, and NPU of proteins in various foods, including eggs, fish, rice, and maize, are listed in Table 8,1 3. 

The quality of a dietary protein may be increased by supplementing the diet with appropriate amino acids. This concept is illustrated by the study shown in Figure 6.29, which involved supplementation of a wheat-based diet with lysine. The chajtge in the quality of the diet was determined simply by measuring changes in the growth rate... 

Protein is an essential nutrient for human growth, development, and homeostasis. The nutritive value of dietary proteins depends on its amino acid composition and digestibility. Dietary proteins supply essential amino acids, which are not synthesized in the body. Nonessential amino acids can be synthesized from appropriate precursor substances (Chapter 17). In human adults, essential amino acids are valine, leucine, isoleucine, lysine, methionine, phenylalanine, tryptophan, and threonine. Histidine (and possibly arginine) appears to also be required for support of normal growth in children. In the absence from the diet of an essential amino acid, cellular protein synthesis does not occur. The diet must contain these amino acids in the proper proportions. Thus, quality and quantity of dietary protein consumption and adequate intake of energy (carbohydrates and lipids) are essential. Protein constitutes about 10-15% of the average total energy intake. 

Dietary protein provides organic nitrogen and the essential amino acids. The quantitative estimation of protein requirement must take into account the quality of protein, as determined by its essential amino acid composition. Dietary protein should provide all of the essential amino acids in the appropriate amounts. If the concentration of one amino acid is significantly greater or less than that of the others (in a protein or amino acid mixture), utilization of the others may be depressed and will be reflected in growth failure. 

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