Effect of defaunation on the metabolism of rumen micro-organisms

Abstract

1. Rumen contents of a fasted fistulated wether, obtained in a faunated, defaunated and refaunated period were incubated in vitro with a mixture of cellobiose and maltose, in the presence of ammonium bicarbonate and32PO43−. Total synthesis of microbial N (Nt) was calculated from32P incorporation and N:P determined in microbial matter. The N:P value was not affected by defaunation. Net synthesis of microbial N (Nn) was calculated from ammonia-N incorporation. An estimate of degradation of microbial N was calculated as Nt–Nn. Energetic efficiency of synthesis was calculated from the volatile fatty acids produced during incubation, as g N incorporated per kg organic matter fermented (g N/kg OMf).2. Defaunation decreased the proportions of acetate, butyrate and methane and increased those of propionate in fermentation end-products. Fermentation rate when expressed per mg microbial N was not affected by defaunation.3. Expressed per unit volume of rumen contents, Nnwas increased by defaunation whereas Nfremained unchanged. Thus, a decrease in degradation can be calculated. Energetic efficiences of total and net synthesis were increased from 35 and 13 to 47 and 30 g N/kg OMfrespectively.4. Specific rates of both total and net synthesis of microbial N were significantly increased by defaunation whereas the specific rate of degradation was not affected.

Effect of defaunation on protein and fibre digestion in sheep fed on ammonia-treated straw-based diets with or without maize

“…The low contribution of protozoal N in the duodenal-N flow only compensated for the decrease in bacterial N generally observed after inoculation of protozoa in a defaunated rumen . Considering the terms 'total' and 'net' synthesis (Demeyer & Van Nevel, 1979), both were probably increased in defaunated rumen by the maize supplementation, but only 'total ' synthesis was increased in faunated rumen. An increase in the difference between 'total' and 'net' synthesis in the faunated rumen is the result of an increase in the degradation (autolysis and predation) of microbial-N, presumably due to protozoal predation of bacteria.…”

“…These results suggested that defamation might have a positive effect on the intestinal protein supply. This has been well evidenced in the last decade by a number of in vitro, in sacco and in vivo digestion trials (Demeyer & Van Nevel, 1979;Kayouli et al 1983Kayouli et al , 1986Veira et al 1983;Ushida et al 1984Ushida et al , 1986Rowe et al 1985;Ushida & Jouany, 1985;Meyer et al 1986).…”

Use of some novel alternative electron sinks to inhibit ruminal methanogenesis

“…Calculations based on VFA production stoichiometry [9] would have then overestimated apparently fermented OM (FOM). Therefore, FOM and substrate apparently fermented were calculated by mass balance from the net production of VFA, lactate, gases, and ammonia.…”

Effect of microbial oil and fish oil on rumen fermentation and metabolism of fatty acids in artificial rumen

“…Neutral detergent fibre, acid detergent fibre, cellulose and hemicellulose in feed and residual feed samples were analysed by the method of Goering and Van Soest (1970). The other fermentation variables, energetic efficiency of VFA (Ørskov et al, 1968) and OMF, organic matter fermented (Demeyer and Van Nevel, 1979), were calculated from the stoichiometry of rumen fermentation.…”