Nitrogen digestibility

Waghom GC, Stafford KJ. Gas production and nitrogen digestion by rumen microbes from deer and sheep. New Zealand Journal Agricultural Research. 1993 36 493-497. 

In the net protein ratio (NPR) calculation (17), 15-day growth and protein intake data of animals on the PER diets were used. Nitrogen digestibility (percent of nitrogen intake absorbed) was determined on each animal on pooled data from the 8th through the 15th day of the PER test. 

Dietz, B. A., Hagerman, A. E., and Barrett, G. W. (1994). Role of condensed tannin on salivary tannin-binding proteins, bioenergetics and nitrogen digestibility in Micro-tuspennsylvanicus. Journal of Mammalogy 75,880-889. 

Machelboeuf, D., Marangi, M., Poncet, C. and Martin-Rosset, W. (1995) Study of nitrogen digestion from different hays by the mobile bag technique in horses. Annales de Zootechnie 44, Supplement 219. 

All human tissues are capable of synthesizing the nonessential amino acids, amino acid remodelling and conversion of non-amino-acid carbon skeletons into amino acids and other derivatives that contain nitrogen. However, the liver is the major site of metabolism of nitrogenous compounds in the body. Dietary proteins are the primary source of essential amino acids (or nitrogen). Digestion of dietary proteins produces amino acids, which are absorbed through epithelial cells and enter the blood. Various cells take up these amino acids that enter the cellular pools. 

These reactions create cross-links between the protein chains, which are responsible for the loss in the nutritive value of the severely heated proteins. This loss can be attributed either to the reduction of the total nitrogen digestibility or to the reduction of the availability of the lysine residues engaged in such isopeptides. 

Behavior of the Protein-Bound Isopeptides. The problem of protein-bound isopeptide absorption was investigated by Hurrell et al. (76) who found that these two isopeptides were not present in greater concentration than the other nitrogen compounds in the ileal and fecal contents of rats that were fed heat-treated protein containing aspartyl-and glutamyllysine. They proposed that the loss in the nutritive value of severely heated proteins was mainly due to a decrease in the nitrogen digestibility. The isopeptides appeared to be either absorbed by the intestine or metabolized by the intestinal microflora. 

Nutritional and Physiological Effects of Alkali-Treated Proteins. The first effect of the alkaline treatment of food proteins is a reduction in the nutritive value of the protein due to the decrease in (a) the availability of the essential amino acids chemically modified (cystine, lysine, isoleucine) and in (b) the digestibility of the protein because of the presence of cross-links (lysinoalanine, lanthionine, and ornithinoalanine) and of unnatural amino acids (ornithine, alloisoleucine, / -aminoalanine, and D-amino acids). The racemization reaction occurring during alkaline treatments has an effect on the nitrogen digestibility and the use of the amino acids involved. 

Adverse effects of exposing proteins to alkaline conditions are known. As early as 1913, it was shown that severely alkali-treated casein fed to dogs was eliminated unchanged in the feces, that it was not attacked by putrefactive bacteria and that trypsin or pepsin was unable to hydrolyze it (9). Ten Broeck reported that egg albumin treated with 0.5 N. NaOH for 3 weeks at 37° had no immunological properties (10). The nitrogen digestibility values of 0.2 M and 0.5 M NaOH-treated casein (80°C, 1 hr), as determined in rats, was 71 and 47%, respectively, as... 

Self-preservation. Blue-green bacteria deprived of a source of nitrogen digest their least-essential proteins. Which phycobilisome component is likely to be degraded first under starvation conditions ... 

The values for faecal nitrogen digestibility (or crude protein digestibility) are given for all the species. In the case of rabbits and fish, these data are, in these tables, the only estimates of the nitrogen values of feed materials. 

The apparent nitrogen digestibility values (Nd) of the feed materials in the database were quite variable, as they had been calculated using the difference method. Therefore, the Nd values were calculated using the following prediction equation for undigested crude protein (UDCP in % dry matter) ... 

The values of total crude protein, of nitrogen digestibility and MADC published in the tables were compared with those of previous INRA tables. 

Although carbon dioxide is the major gas contributing to chmate change, methane and nitrous oxide are also significant contributors because of their warming potentials, which are 25 and 300 times that of carbon dioxide, respectively. The consequences of nitrogen digestion and metabohsm on the environment are considered in Chapter 13. 

Molina DO, PeU AN, Hogue DE (1999) Effects of ruminal inoculations with tannin-tolerant bacteria on fibre and nitrogen digestibility of lambs fed a high condensed tannin diet. Anim Feed Sci Technol 81 669-680... 

Fermentation is known to improve protein quality due to higher nitrogen digestibility and the de novo production of some amino acids such as lysine and tryptophan. In addition, these processes lower the presence of antinutritional factors (Chavan and Kadam 1989a). 

Jakkola, S. and P. Huhtanen, 1993. The effects of the forage preservation method and the proportion of concentrate on nitrogen digestion and rumen fermentation in cattle. Grass Forage Sci. 48, 146-154. 

Vanhatalo, A., I. Aronen and T. Varvikko, 1995. Intestinal nitrogen digestibility of heat-moisture treated rapeseed meals as assessed by the mobile-bag method in cows. Anim. Feed Sci. Technol. 55, 139-152. 

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