Quantitative effects of defaunation on rumen fermentation and digestion in sheep

Abstract

1. Studies on the quantitative significance of protozoa on carbon and nitrogen digestion and metabolism in the rumen were carried out in sheep given a diet of pelleted concentrate (500 g/d) and chopped hay (500 g/d).2. Measurements were made of apparent digestibility; flows of organic matter and dietary and microbial non-ammonia N (NAN) (using 16NH:) to the duodenum; and rates of production, interconversion and metabolism of the major C fermentation end-products (from mathematical modelling of 14C isotope values).3. The population density of bacteria in the rumen increased as a result of defamation (28.6 compared with 8.2 x lo0 organisms/ml). This high density was associated with greater utilization of volatile fatty acids (VFA) within the rumen.4. The rate of irreversible loss (IL) of bicarbonatefcarbon dioxide from the rumen was greater in the defaunated animals (98.5 v. 57.2 g C/d) but the IL from the blood was greater in the faunated group (138.6 v. g C/d). This is consistent with the hypothesis that the high population density of bacteria found in the rumen fluid of defaunated animals may result in increased fermentation of rumen VFA and digestible dietary carbohydrate, thereby increasing the output of CO, from the rumen and reducing the quantity of VFA (hence energy) available to the host.5. There was no difference in the flow of organic matter (OM) to the duodenum but there was a higher faecal excretion of OM in defaunated animals (apparent OM digestibility: 0.72 in faunated, 0.67 in defaunated).6. Defamation did not significantly increase the flow of NAN to the duodenum, the percentage of duodenal NAN of bacterial origin or the quantity of microbial NAN synthesized/g organic matter fermented. Faecal excretion of NAN was higher in defaunated animals (5.3 v. 3.6 g N/d).

The effects of protozoa and of supplementation with nitrogen and sulfur on digestion and microbial metabolism in the rumen of sheep

“…This contrasts with the response of extremely S deficient sheep in which rumen H2 accumulates to abnormal levels and in which S supplements are known to stimulate methanogenesis and alleviate Hz build-up (Hegarty et al 1991). Fauna-free ruminants have previously been observed to produce less methane than faunated ruminants (Rowe et al 1985;Ushida et al 1986), but the difference was not significant in this study.…”

Effect of selected rumen fauna on the digestion of starch and outflow of α-glucose polymers from the reticulo-rumen of sheep

“…It is also suggested that the rumen ciliates degrade and ferment starch much more slowly than bacteria (McAllister and Cheng, 1996). The obtained results are in line with the findings of Mendoza et al (1993) on the effect of a mixed fauna, but in disagreement with the data of Veira et al (1983) and Rowe et al (1985). The outflow rate from the reticulum was calculated according to Michałowski (1998).…”

“…This dietary polysaccharide is digested and fermented by bacteria, fungi and protozoa inhabiting the rumen. The role of protozoa in starch metabolism is controversial (Veira et al, 1983;Rowe et al, 1985;Mendoza et al, 1993). It is well known, however, that all of the examined species exhibit amylolytic activity (Williams and Coleman, 1992).…”

Die Bedeutung der Protozoen im Pansen von Hammeln für Verdaulichkeit, N‐Bilanz und N‐Fraktionen in Kot und Harn bei unterschiedlichen Gehalten und Arten von Stärke in der Ration

“…23,9 f 10,5 (KLOPFENSTEIN et al 1966;EADIE und GILL 1971;KURIHARA et al 1978;ROWE et al 1985). Wenn aber beriicksichtigt wird, daB Protozoen bis zu 50% der Bakterien retinieren (KURIHARA et al 1968;RUSSELL 1984) KELLNER et al 1985).…”