Reponses of sheep to a vaccination of entodinial or mixed rumen protozoal antigens to reduce rumen protozoal numbers

Abstract

Two rumen protozoa vaccine formulations containing either whole fixed Entodinium or mixed rumen protozoa cells were tested on Merino sheep with the aim of decreasing the number and/or activity of protozoa in the rumen. Negative control (no antigen) and positive control (Tetrahymena corlissi antigens) treatments were also included in the experiment. Blood and saliva were sampled to measure the specific immune response. Protozoal numbers in the rumen were monitored by microscopic counts. Vaccination with protozoal formulations resulted in the presence of specific IgG in plasma and saliva, but saliva titres were low. Titres after secondary vaccination were higher (P,0·05) than after primary vaccination. There was a moderate (r 2 0·556) relationship (P, 0·05) between plasma and saliva titres for the rumen protozoal vaccine formulations. Rumen protozoa were not decreased (P. 0·05) by the vaccination and there was also no difference (P.0·05) between treatments in rumen fluid ammonia-N concentration or wool growth. In vitro studies investigated the binding ability of the antibodies and estimated the amount of antibody required to reduce cell numbers in the rumen. The studies showed that the antibodies did bind to and reduced protozoa numbers, but the amount of antibody generated by vaccination was not enough to produce results in an in vivo system. It is suggested that the vaccine could be improved if specific protozoal antigens are determined and isolated and that improved understanding of the actions of protozoa antibodies in rumen fluid and the relationships between levels of antibodies and numbers of protozoa in the rumen is needed. Antigens: Antibodies: Rumen protozoa: SheepThe rumen is populated with many types of micro-organisms, which degrade and ferment the feed eaten by the animal. However, from a production point of view, not all the micro-organisms present in the rumen are essential or provide efficient conversion of feed to protein 1 . Many studies have shown that if protozoa are removed from the rumen, a process known as defaunation, wool growth can be increased due to increased microbial protein outflow to the small intestine 1 -3 . However, successful defaunation methods can be laborious and impractical in normal animal husbandry settings and chemical-based methods can be detrimental to animal health 3,4 . Also, unless defaunated animals remain segregated from faunated animals, or are regularly re-treated with defaunation chemical, the ciliated protozoa are able to re-establish themselves in the rumen. An immunological approach to manipulating rumen microbial populations, specifically rumen ciliates, was investigated by Gnansampanthan 5 . Serum antibodies raised to rumen ciliates were shown to have an immobilizing effect on a mixed rumen ciliate population in vitro, which decreased the ciliates' predatory activity on bacteria 6 . Until now there has been no in vivo examination of the effects that protozoal vaccines have on the numbers of ciliate protozoa in the rumen. The aim of the present experiment w...

A Vaccine against Rumen Methanogens Can Alter the Composition of Archaeal Populations

“…On a DM basis, it contained 93% organic matter, 9% crude protein, 42% neutral detergent fiber, and 22% acid detergent fiber. Methods used for collection and analysis of feed samples have been described by Williams et al (25). After 4 weeks of acclimatization to the experimental diet, rumen fluid (30 to 50 ml) for construction of 16S rRNA gene libraries was collected from all sheep by insertion of a stomach tube and application of suction 2 to 3 h after they were fed.…”

Ruminal microorganism consideration and protein used in the metabolism of the ruminants: A review

“…However, the flow out of the rumen protozoa is not proportional to its number in the rumen. Protozoa are retained because of biomass selectively in the rumen (Williams et al, 2008). The removed of rumen protozoa increases the flow of microbial and dietary protein to duodenum.…”

Progress in the development of vaccines against rumen methanogens

“…Methanogens associated with protozoa may shift the fermentation of the latter to produce more hydrogen and hence methane formation, and so the presence of protozoa may increase ruminal methane formation. Williams et al (2008) reported a vaccination trial in sheep using either whole fixed Entodinium or mixed rumen protozoal cells. Administration of these vaccines induced specific antibody responses in blood and saliva, but there was no significant decrease in protozoal numbers following vaccination.…”

“…A recent study has shown that antibodies generated against rumen protozoa can remain active for up to 8 h (Williams et al, 2008). However, little is known about the resistance of different classes of antibodies, such as IgG and IgA, to degradation by proteases and peptidases present in the hydrolytic environment of the rumen and how long these antibodies will remain biologically active.…”

“…Although the entry of saliva into the rumen of vaccinated animals will provide a constant replenishment of anti-methanogen antibodies in the rumen, these antibodies will need to persist long enough within the rumen environment to interact effectively with their intended targets on methanogens. The stability of antibodies in the rumen may not be a limitation, as studies have suggested that antibodies can persist for up to 8 h in the rumen (Williams et al, 2008). It is usually observed, and understood from theory, that inhibiting methane formation will increase ruminal propionate production at the expense of acetate and hydrogen.…”