title: 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 and 32PO43-. Total synthesis of microbial N (Nt) was calculated from 32P 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, Nn was increased by defaunation whereas Nt remained 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 OMf respectively. 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.
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents; D000981:Antiprotozoal Agents; D001419:Bacteria / Q000378:metabolism*; D004143:Dioctyl Sulfosuccinic Acid / Q000494:pharmacology*; D056890:Eukaryota / Q000378:metabolism*; D005232:Fatty Acids, Volatile / Q000378:metabolism; D005285:Fermentation; D008297:Male; D009584:Nitrogen / Q000378:metabolism*; D012417:Rumen / Q000382:microbiology*; D012756:Sheep; D013386:Succinates / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D000981:Antiprotozoal Agents; D005232:Fatty Acids, Volatile; D013386:Succinates; D004143:Dioctyl Sulfosuccinic Acid; D009584:Nitrogen