The utilization of non-protein nitrogen in the bovine rumen. 5. The isolation and nutritive value of a preparation of dried rumen bacteria

Abstract

the disulphide bond in the wool at all until considerable degradation has occurred. Simple cystine polypeptides of varying compositions are now being synthesized to determine in which stereochemical arrangement if any the cystine disulphide bond cannot be oxidized by hypochlorite and permanganate. SUMMARY 1. A study has been made of the reaction of the disulphide bond in wool with different oxidizing agents. 2. Chlorine, hypochlorous acid and peracetic acid are capable of oxidizing all the cystine in wool, whereas acid permanganate and alkaline hypo-chlorite are only capable of oxidizing 25 % of the cystine present. The cystine in wool may therefore be divided into two fractions, one ofwhich is oxidized by the latter two reagents, and the other not. 3. The difference in reactivity of the two cystine fractions cannot be ascribed to morphological causes since the cystine of physically modified wools and powdered horn shows the same division. 4. The two fractions are not related to the Phillips (1946) cystine fractions. Possible explanations for the differences in reactivity are discussed. The authors wish to thank Messrs Wolsey Ltd., Leicester, for financial support which made this investigation possible, Prof. H. V. A. Briscoe for his help and interest, and Mr D. Gough for carrying out some of the preliminary experiments. * Previous papers in this series were published under the general title 'The Utilization of Urea in the Bovine Rumen'; see Smith & Baker (1944).

The Growth and Composition of Wool IV. The Differential Response of Growth and of Sulphur Content of Wool to the Level of Sulphur-Containing Amino Acids given Per Abomasum

“…Thus, the amount of nitrogen reaching the duodenum on this diet il3 similar to the nitrogen intake and is probably mainly microbial nitrogen (Hogan, unpublished data). When allowances are made for non-amino nitrogen (Hogan 1965), for the digestibility of rumen microbial protein (McNaught et al 1950(McNaught et al , 1954Reed, Moir, and Underwood 1949) and for the amino acid composition of this protein (Hungate 1966) only about 1· 0-1· 5 g/day S-amino acids would be available for absorption.…”

Studies on the digestibility and utilization of the nitrogen of irradiated rumen bacteria by rats

“…Several workers have attempted to avoid some of these problems by determining the nitrogen digestibility of bacteria isolated from rumen contents in experiments with rats, the assumption being that these animals digest bacterial nitrogen to the same degree as do ruminants (Johnson et al 1944;Reed, Moir & Underwood, 1949;McNaught et al 1950;McNaught et al 1954;Bergen, Purser & Cline, 1968). However, the true nitrogen digestibility and biological value estimates obtained by these workers differed considerably between laboratories, possibly reflecting differences in the methods used for isolating and drying the bacterial preparations.…”

The chemical composition of rumen bacteria and cell walls from rumen bacteria

“…A number of experiments carried out to determine the nutritional value of rumen bacteria (Johnson, Hamilton, Robinson & Garey, 1944; Reed, Moir & Underwood, 1949; McNaught, Smith, Henry & Kon, 1950) have shown that they are as good a source of protein for rats as casein or gelatin. It is apparent therefore that rumen bacteria are of potential importance in the nutrition of sheep.…”