Some factors influencing the chemical composition of mixed rumen bacteria

Abstract

I. Sheep, cows and calves fitted with rumen cannulas were given diets mostly containing 10-16 g nitrogen/kg dry matter and consisting of roughage and cereals. Mixed bacteria w-ere separated from samples of their lumen contents.2. Bacteria taken 4-6 h after a feed from calves which were kept in an experimental calfhouse with no contact with adult animals (environment -4) contained more a-dextran, less total N and higher nucleic acid : total N ratios than similar bacteria from calves reared in contact with adult sheep (environment C ) but otherwise treated in an identical way. 3.Mixed bacteria taken 4-6 h after a feed from sheep and cows were similar in composition, with respect to nitrogenous components, to those from the 'environment C' calves. This composition did not vary significantly when diets containing differing proportions of roughage were given. 4 . The 'environment A' calves were free of ciliate protozoa. When they were placed in contact with, and were inoculated with rumen contents from, adult cattle (environment B), they rapidly developed a normal protozoal population and the chemical composition of their rumen bacteria became like that of the bacteria from the 'environment C' calves.5 . Mixed bacteria taken just before a feed, from either cows or 'environment A' calves, showed significantly lower RNA-N : total N ratios and slightly (but not usually significantly) higher DNA-N:total N ratios than bacteria taken 4-6 h after feeding. Total N contents of the bacteria did not change consistently with time after feeding.6 . The possible significance of these differences in relation to the nutrition of the host animal is discussed.The bacterial population in the rumen generally contributes a considerable part of the nutrient material entering the small intestine of the ruminant. Knowledge of the chemical composition of this population and how it varies is necessary for a proper understanding of the nutrition of the host animal and to enable calculations to be made, for example, of the contribution of bacterial protein and carbohydrate to the digesta. Results, gencrally for small numbers of samples, have been reported for total nitrogen, amino acids, nucleic acids, carbohydrates, lipids and ash as proportions of the dry matter in some samples of mixed rumen bacteria

The Microbial Contribution to Human Faecal Mass

“…The composition of rumen microflora has been studied by isolating bacteria by filtering and centrifugation (Hoogenraad and Hird, 1970;Smith and McAllan, 1974). This approach was also applied early in this century to the quantitation of the bacteria in human faeces and gave values of around 30% for the bacterial component of faecal solids, (MacNeal, Latzer and Kerr, 1909).…”

“…We have therefore developed a method that fractionates faeces into three main components: the bacteria, undigested fibre, and soluble substances. The procedure has been developed from techniques used to isolate microbial matter from the rumen (Hoogenraad and Hird, 1970;Smith and McAllan 1974), with several steps altered or omitted to improve the separation of bacteria from fibrous debris and to ensure the purity of the bacterial fraction. By this method, a direct estimate of the microbial contribution to the weight of the stool has been obtained.…”

Estimation of microbial protein supply in ruminant animals based on renal and mammary purine metabolite excretion. A review

“…Concentrations of NA and N (65-100 and 70-110 mg/g OM, respectively) in rumen bacteria (Smith and McAllan, 1974;Czerkawski, 1976;Storm and Orskov, 1983) tend to be marginally higher (50-90 and 40-90 mg/g OM, respectively) than in rumen protozoa (Czerkawski, 1976;Olubobokun etal., 1988;Stokes et al, 1991;Martin etal., 1994;Robinson etal., 1996). Some studies have reported similar ratios of RNA:N (McAllan, 1982) or purine:N (Czerkawski, 1976;Volden et al, 1999) in rumen bacteria and protozoa, while other studies have indicated lower ratios in protozoa (Ling and Buttery, 1978;Arambel et al, 1982;Firkins et al, 1987;Stokes et al, 1991;Kanjanapruthipong and Leng, 1998).…”

Factors influencing the digestion of dietary carbohydrates between the mouth and abomasum of steers

“…Analytical Dry matter (DM) and OM were determined as described by Smith et al (1978). Feed or digesta samples were subjected to acid-hydrolysis (McAllan & Smith, 1974) which released ribose, mannose, galactose, arabinose, xylose and starch-glucose. Amounts of these sugars were measured by ion-exchange chromatography of their borate complexes (McAllan 8z Smith, 1974).…”