Study of the effect of presence or absence of protozoa on rumen fermentation and microbial protein contribution to the chyme1

Abstract

The aim of this study was to investigate the effect of presence or absence of protozoa on rumen fermentation and efficiency of microbial protein synthesis under different diets. Of 20 twin paired lambs, 1 lamb of each pair was isolated from the ewe within 24 h after birth and reared in a protozoa-free environment (n = 10), whereas their respective twin-siblings remained with the ewe (faunated, n = 10). When lambs reached 6 mo of age, 5 animals of each group were randomly allocated to 1 of 2 experimental diets consisting of either alfalfa hay as the sole diet, or 50:50 mixed with ground barley grain according to a 2 × 2 factorial arrangement of treatments. After 15 d of adaptation to the diet, the animals were euthanized and total rumen and abomasal contents were sampled to estimate rumen microbial synthesis using C(31) alkane as flow marker. Different ((15)N and purine bases) and a novel (recombinant DNA sequences) microbial markers, combined with several microbial reference extracts (rumen protozoa, liquid and solid associated bacteria) were evaluated. Absence of rumen protozoa modified the rumen fermentation pattern and decreased total tract OM and NDF digestibility in 2.0 and 5.1 percentage points, respectively. The effect of defaunation on microbial N flow was weak, however, and was dependent on the microbial marker and microbial reference extract considered. Faunated lambs fed with mixed diet showed the greatest rumen protozoal concentration and the least efficient microbial protein synthesis (29% less than the other treatments), whereas protozoa-free lambs fed with mixed diet presented the smallest ammonia concentration and 34% greater efficiency of N utilization than the other treatments. Although (15)N gave the most precise estimates of microbial synthesis, the use of recombinant DNA sequences represents an alternative that allows separate quantification of the bacteria and protozoa contributions. This marker showed that presence of protozoa decrease the bacterial-N flow through the abomasum by 33%, whereas the protozoa-N contribution to the microbial N flow increased from 1.9 to 14.1% when barley grain was added to the alfalfa hay. Absolute data related to intestinal flow must be treated with caution because the limitations of the sampling and maker system employed.

In vitro methane formation and carbohydrate fermentation by rumen microbes as influenced by selected rumen ciliate species

“…fatty acid (SCFA) profile (Williams and Coleman 1992;Eugène et al 2004;Belanche et al 2011a) and methanogenesis (Soliva et al 2003) were not consistent between studies. Likewise, digestibility of organic matter (OM) and fiber is not always (Kasuya et al 2007;Zeitz et al 2012), but often (Eugène et al 2004;Belanche et al 2011a) higher in faunated animals.…”

“…Likewise, digestibility of organic matter (OM) and fiber is not always (Kasuya et al 2007;Zeitz et al 2012), but often (Eugène et al 2004;Belanche et al 2011a) higher in faunated animals. In the latter case, hemicellulose degradation seems to be stronger inhibited by defaunation than cellulose digestion (Chaudhary et al 1995).…”

“…Apart from degrading carbohydrates like other ruminal microbes, they specifically influence growth and activity of rumen bacteria and methanogenic Archaea. A general influence of the protozoa in this respect has been mainly explored by comparing the fermentation capacity of ruminants with intact or defaunated, i.e., protozoa-free, rumen microbial populations (Eugène et al 2004;Morgavi et al 2008;Belanche et al 2011a). However, defaunation-induced changes like those found for instance in ruminal short-chain * Corresponding author.…”

Rumen microorganisms and fermentation

“…In addition, the decrease in postprandial pH is regulated by protozoa (Belanche et al 2011) because they modulate amylolytic bacterial populations, which use glucose from starch as a substrate for its fermentation processes to give lactate as one of its main products (Mendoza et al 1993). Belanche et al (2011), showed that presence of rumen protozoa increased rumen total VFA and ammonia-N significantly, when the ruminal protozoa are present. Hence there exists a positive response on fiber digestibility and VFA concentration to fautation, especially when structural carbohydrates represent the principal dietary component, this confirms the actions of protozoa to fribrolytic activity (Belanche et al 2011).…”

“…Therefore, although protozoa are not essential for ruminant growth, its presence is important because of its ability to degrade the main components, which is an important role in the fermentation process (Coleman 1985). In addition, the decrease in postprandial pH is regulated by protozoa (Belanche et al 2011) because they modulate amylolytic bacterial populations, which use glucose from starch as a substrate for its fermentation processes to give lactate as one of its main products (Mendoza et al 1993). Belanche et al (2011), showed that presence of rumen protozoa increased rumen total VFA and ammonia-N significantly, when the ruminal protozoa are present.…”