Effect of Ammonia Concentration on the Composition, Hydrolytic Activity and Nitrogen Metabolism of the Microbial Flora of the Rumen

Abstract

The mean NH3 concentration in the rumen of sheep fed whole barley (0d̀8 kg/d) by continuous feeders was increased from 6d̀1 to 13d̀4 HIM by supplementing the feed with urea (30 g/kg). This change caused a 90% increase in the rate of degradation of rolled barley, and smaller increases in the rates of degradation of protein and plant fibre in the rumen. The total viable count and numbers of pectinolytic bacteria in rumen fluid increased with the urea supplement. Enzyme studies indicated that NAD‐linked glutamate dehydrogenase was the main pathway of NH3 assimilation by rumen bacteria at both NH3 concentrations. Glutamate was the main free amino acid found in the rumen at low NH3 but, despite the low activity of alanine dehydrogenase and glutamate‐pyruvate aminotransferase, alanine was the principal amino acid at high NH3 concentrations. Hydrolytic rumen bacteria may require the higher NH3 concentration either for effective NH3 assimilation by an unknown mechanism involving alanine or for full expression of enzyme activity.

Distribution and changes in urease (EC3.5.1.5) activity in Rumen Simulation Technique (Rusitec)

“…The importance of adherent microbial population in the rumen has been recognized , and in fact Cheng & Wallace (1979) suggested that urease production is largely a function of bacteria attached to the sloughed epithelial cells. Since there are no such cells in Rusitec, the source of urease must be different.…”

In vitro and in situ activity of carboxymethyl cellulase and glutamate dehydrogenase according to supplementation with different nitrogenous compounds

“…This may be due to a higher concentration of AN in these treatments. The k m of GDH for ammonia is 20 to 33 mM, which corresponds to 34 to 56 mg/dL, respectively (Erfle et al, 1977;Wallace, 1979). Furthermore, no difference in the GDH activity was detected among treatments in situ (Table 4).…”

Effects of ammonia concentration and microbial population on in vitro degradation of 14C-labelled dietary proteins

“…These resulrs suggest that ammonia concentration for maximal microbial growth may not be equal to concentration required for optimal rate of ruminal protein degradation. Wallace (1979) reported that increased dry matter (DM) and protein degradation in situ was accompanied by increased bacterial growth when amrnonia concentration was increased from 9.i to 21.4 mg dl--r ruminal fluid. In contrast.…”

“…Wallace and Brammall (1985) Crooker et al (1978) and Crawford et al (1978) For personal use only. (Wallace 1979 (1973) indicated that barley grain has a higher fermentability than maize and deFaria and Huber (1985) …”