Metabolism of nitrogenous compounds in the large gut

Mason, V. C.

doi:10.1079/pns19840026

Cited by 86 publications

(37 citation statements)

References 65 publications

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“…Microbial fermentation of protein in the colon yields amines, ammonia, phenols and other nitrogenous compounds, some of which cross the gut wall and enter the blood stream and urine. However, unlike microbial fermentation of starch, the products of microbial fermentation of protein appear to provide no energy to the consumer (Mason, 1984;McNeil, 1988;Birkett et al, 1996).…”

Section: Increased Digestibilitymentioning

confidence: 99%

The energetic significance of cooking

Carmody¹,

Wrangham²

2009

Journal of Human Evolution

338

220

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While cooking has long been argued to improve the diet, the nature of the improvement has not been well defined. As a result, the evolutionary significance of cooking has variously been proposed as being substantial or relatively trivial. In this paper, we evaluate the hypothesis that an important and consistent effect of cooking food is a rise in its net energy value. The pathways by which cooking influences net energy value differ for starch, protein and lipid, and we therefore consider plant and animal foods separately.Evidence of compromised physiological performance among individuals on raw diets supports the hypothesis that cooked diets tend to provide energy. Mechanisms contributing to energy being gained from cooking include increased digestibility of starch and protein, reduced costs of digestion for cooked versus raw meat, and reduced energetic costs of detoxification and defense against pathogens. If cooking indeed consistently improves the energetic value of foods through such mechanisms, its evolutionary impact depends partly on the relative energetic benefits of non-thermal processing methods used prior to cooking.We suggest that if non-thermal processing methods, such as pounding, were used by Lower Paleolithic Homo, they likely provided an important increase in energy gain over unprocessed raw diets. However, cooking has critical effects not easily achievable by nonthermal processing, including the relatively complete gelatinization of starch, efficient denaturing of proteins, and killing of foodborne pathogens. This means that however sophisticated the non-thermal processing methods were, cooking would have conferred incremental energetic benefits. While much remains to be discovered, we conclude that the adoption of cooking would have led to an important rise in energy availability. For this reason, we predict that cooking had substantial evolutionary significance.

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Section: Increased Digestibilitymentioning

confidence: 99%

The energetic significance of cooking

Carmody¹,

Wrangham²

2009

Journal of Human Evolution

338

220

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“…This may be due to the stimulating effect of fermentable carbohydrates on cecal bacterial proliferation. Ammonia may be a main N source for bacterial growth since a drop in unionized ammonia concentration has been reported (Mason, 1984). D-mannitol decreases the blood urea N and urinary N excretion The increase in urea transfer from the blood to the large intestine by fermentable carbohydrates results in a decrease in blood urea N and N excretion in the urine (Younes et al, 1995a and1995b).…”

Section: Weight Of Gutmentioning

confidence: 99%

Transfer of blood urea nitrogen to cecal microbial nitrogen is increased by mannitol feeding in growing rabbits fed timothy hay diet

Xiao

Jin

et al. 2012

Animal

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The presence of the fermentable sugar D-mannitol in the diet improves nitrogen (N) utilization in rabbits. To clarify the mechanism by which D-mannitol improves N utilization, we studied the effect of D-mannitol on the fate of blood urea N in growing rabbits. Growing rabbits received a control diet or a diet containing D-mannitol, which were formulated by adding 80 g/kg glucose or D-mannitol to timothy hay. After 9 days of feeding of the experimental diets, 15 N-urea was administrated intravenously under anesthesia 1 h before slaughter. The blood urea level (concentration of both urea N (43.6% of the control group (CG), P , 0.05) and 15 N (95% of the CG, P , 0.05) in blood serum) was reduced in the mannitol group. The concentration and amount of N, and 15 N atom % excess in the contents of the cecum and colon were higher (P , 0.05) in the rabbits fed the mannitol diet than in rabbits fed the control diet, especially in the cecum. The consumption of mannitol caused bacterial proliferation in the cecum characterized by marked short-chain fatty acid production (165% of the CG, P , 0.05), decreased cecal ammonia N (73% of the CG, P , 0.05) and elevated cecal bacterial N (150% of the CG, P , 0.05). On the other hand, addition of D-mannitol to the diet decreased N (80% of the CG, P , 0.05) and 15 N (77% of the CG, P , 0.05) excretion in the urine. These results indicate that D-mannitol increases the transfer of blood urea N to the large intestine, where it is used for bacterial N synthesis.Keywords: fermentable sugar, D-mannitol, nitrogen, growing rabbits ImplicationsCecotrophy allows rabbits to reingest microbial products from the cecum as cecotrophs. Cecotrophy has considerable significance for nitrogen (N) metabolism in rabbits. A previous study indicated that as a fermentable sugar, D-mannitol increases N utilization through cecotrophy by deceasing urinary N excretion in rabbits. In the present study, we clarified the possible mechanism by which D-mannitol improves N utilization in growing rabbits. The results indicate that D-mannitol can be used as a cecal microbial stimulator to promote the utilization rate of dietary N in rabbits fed a diet of timothy hay. Moreover, it might aid in reducing the N load passed on to the environment. IntroductionIt is well documented that fermentable carbohydrates can increase urea flux from the blood to the digestive tract and alter fermentation in the large intestine of rats (Ré mé sy and Demigné, 1989;Younes et al., 1995b;Henningsson et al., 2002). In rabbits, a considerable portion of endogenous urea is transferred to the alimentary tract (Regoeczi et al., 1965), and the exchange between blood urea nitrogen (N) and cecal ammonia N is well established Parker, 1985a and1985b). However, the exact fate of blood urea in rabbits fed a diet containing fermentable sugar remains unclear.Urea, as an end product of ammonia and protein metabolism, is synthesized in the liver of mammals and passed into the blood stream (Stewart and Smith, 2005). Most of the blood urea is eliminated ...

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“…Suppression of the microflora resulted in higher activities of pancreatic enzymes in the distal small intestine and large intestine (Boisen et al 1985) compared with conventional rats, in which pancreatic enzymes are rapidly destroyed by the gut flora (Mason, 1984). Enzymatic digestion of protein still in the hindgut and more time available for protein hydrolysis because of longer MTT are the most likely reasons for the higher protein digestibilities in nebacitin-treated rats compared with pigs.…”

Section: Nebacitin-treated Rats As a Modelmentioning

confidence: 99%

The rat as a model for pigs: comparative values for the digestibility of NSP and other macronutrients

Wisker

Knudsen

2003

Br J Nutr

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The present investigation was undertaken to study whether conventional male Wistar rats could be used as a model for pigs with regard to total tract digestibilities of NSP and macronutrients and whether nebacitin-treated rats could be used as a model for small intestinal digestibility in pigs. Nineteen experimental diets prepared from different fractions of wheat and oats, and which all had been evaluated in experiments with ileal cannulated pigs, were used for the present study. There was a close relationship between the total tract digestibilities of organic matter in the two species. The same was the case with regard to the digestibility of total NSP and arabinoxylans, but the values were on average 6 % lower in rats than in pigs. On average, there were no significant differences between rats and pigs with regard to faecal protein digestibility. However, protein in oat-based diets was significantly better digested in the rat than the pig. The digestibility of fat was consistently higher in rats than in pigs, with the biggest difference being found in oat-based diets, in which most of the fat was locked in cell structures. For the wheat-based diets, in which a large proportion of the fat was present as added fat, there was a greater similarity between the two species. In nebacitin-treated rats the digestibility of organic matter, starch, protein and fat was negatively related to the dietary level of NSP, but this model could not be used to predict the small intestinal digestibility of NSP and macronutrients in ileal-cannulated pigs.Digestibility: Non-starch polysaccharides: Protein: Fat: Pigs: RatsThe laboratory rat has been widely used to investigate basic principles of nutrition in single-stomached animals. In contrast to human nutrition, however, the use of rats as models in pig nutrition is less well accepted, because it is relatively easy to obtain results from the pig itself. The great value of the rat as a model lies in the economic factors associated with facilities and time, which allows the use of large numbers of animals and a rapid production of results.The digestibility of energy and protein in the pig and rat is highly correlated for several diets (Eggum, 1973;Eggum et al. 1982), indicating that the rat may be a good model for pigs for these variables. However, it is less clear whether rats are also suitable models for pigs with regard to the digestibility of other nutrients and the fermentation of non-digestible carbohydrates, primarily as NSP, by the gut microflora. Like the pig, rats harbour a permanent bacterial flora in the stomach and small intestine, and similar groups of bacteria were found in the large intestine of both species (Jensen, 1992). However, there are obvious differences between rats and pigs that may be of importance for the microbial fermentation. The relative size of the caecum in rats is bigger than in pigs and the rat may practise coprophagy. Further, the rat is a small animal with a faster transit through the gut, and this can reduce bacterial polysaccharide breakdown co...

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Metabolism of nitrogenous compounds in the large gut

Cited by 86 publications

References 65 publications

The energetic significance of cooking

The energetic significance of cooking

Transfer of blood urea nitrogen to cecal microbial nitrogen is increased by mannitol feeding in growing rabbits fed timothy hay diet

The rat as a model for pigs: comparative values for the digestibility of NSP and other macronutrients

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