Protein digestibility diets

The amonnt of protein synthesised and then released in (iv) and (v) is abont 70 g each day. Even under conditions of starvation or malnutrition, proliferation and differentiation of stem cells located in the crypts of the villi are important to provide the cells necessary for replenishment of those lost from the villi. New cells move up the villus to replace those lost at the top. Under these conditions, amino acids are not available from the intestine and have to be taken up from the blood across the basolateral membrane. A low level of amino acids in the blood, due to chronic malnutrition, will prevent or reduce the rate of proliferation of these cells, so that digestion of even the small amount of food ingested during malnutrition, or refeeding after starvation, is difficult. A vicious circle thus results from protein-deficient diets which increase the risk of development of protein-energy-malnutrition. This is especially severe in children but may also contribute to the clinical problems that occur in the elderly whose diets are of low quality. 

Calculate the true protein digestibility using the following equation True protein digestibility = [PI - (FP - MFP)]/PI x 100 where PI equals protein intake (g) FP is fecal protein (g) and MFP is the metabolic fecal protein (g). The MFP is calculated from the amount of protein in the feces of rats fed a protein-free diet (Sarwar, 1996). 

Like all other animals, poultry require five components in their diet as a source of nutrients energy, protein, minerals, vitamins and water. A nutrient shortage or imbalance in relation to other nutrients will affect performance adversely. Poultry need a well-balanced and easily digested diet for optimal production of eggs and meat and are very sensitive to dietary quality because they grow quickly and make relatively little use of fibrous, bulky feeds such as lucerne hay or pasture, since they are non-ruminants (have a simple stomach compartment). 

Figure 2. Effect of Alkylation of Casein By Chlorogenoquinone on in vitro Protein Digestibility and Relative Growth of larval Spodoptera exigua. 1.0% casein was treated CHA concentrations shown and with 0.100 change in OD yQ/min/gm diet PPO. Larval growth and protein digestibility reported as percent control where control equals 100%.

Many experiments have demonstrated the capacity of cellulases and of mixtures of cellulases, pectinases, and hemicellulases to break down or to soften plant cell walls. For human diets this would be beneficial in preparing infant or geriatric foods where reduced fiber content is desired. Recently treatment of wheat bran was found to increase the in vitro protein digestibility by 35% (63) and to increase weight gain of rats fed a bran-containing ration. The aleurone cell wall was the primary substrate for these enzymes. 

Two important zinc metalloenzymes in protein digestion are the pancreatic carboxypeptidase A and B. A loss of activity of the pancreatic carboxyeptidase A in zinc deficiency is a consistent finding (91), According to some investigators, within two days of institution of zinc-deficient diet in rats, the enzyme lost 24% of its activity, and within three days of dietary zinc repletion, the activity of pancreatic carboxypeptidases is restored to normal levels (91). These results indicate that the level of food intake has no influence and that a decreased activity of carboxypeptidase A in the pancreas was related specifically to a dietary lack of zinc. As in the case of the alkaline phosphatase, the amount of carboxypeptidase A apoenzyme present appears to be diminished in zinc-deficient pancreas. 

Walters Options The Alternative Cancer Therapy Book (1993) contains a short introduction to the subject under the section Metabolic Therapies, with the statement that proteolytic (protein-digesting) enzymes are believed to dissolve the walls of cancer cells, and that enzyme treatments are widely used in Europe. More specifically, enzymes are used variously in what are called Issels therapy, in Wheatgrass therapy, in the Gerson diet, in Kelley s therapy, and in Niepa- s therapy (Walters, 1993, pp. 86,147,198,207,216). It is noted furthermore that chranotherapy destroys the body s enzymes, that cooking destroys the enzymes in food, and that enzymes may be involved in the so-called spontaneous remission of cancer (Walters, 1993, pp. 155,201). Also noted, in the work of Hans Niepa-, is that the enzyme bromelain, derived from pineapple roots, will deshield cancer cells, as will beta-carotene (Walters, 1993, p. 222). 

Essential amino acids must be acquired in the diet nonessential amino acids can be synthesized by the body. Complete proteins contain all the essential and nonessential amino acids. Incomplete proteins are missing one or more essential amino acids. Protein digestion begins in the stomach, where proteins are degraded by the enzyme pepsin. Further digestion occurs in the small intestine by enzymes such as trypsin and chymotrypsin. 

Several soy products may be used as protein sources in dog foods. In dry extruded diets, both ileal and total tract crude protein digestibilities of soy-containing diets appear to be equal or superior to diets containing animal protein by-products. On the other hand, in canned foods, texturized vegetable protein can reduce dry matter and crude protein digestibilities by dogs, and soy protein sources usually increase fecal output. A lack of information is apparent on the effects of including soy protein sources in diets fed to cats. 

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