Characteristics of the rumen ciliates and ruminant association
Jouany, J.P.
Station de Recherches Sur la Nutrition des Herbivores, THEIX,
F-63122 St Genès Champanelle, France
Herbivores and more especially ruminants make up a large share of the domestic animals involved in production of food for humans. Their main characteristic is that they can utilize the cellulosic materials non usable by the rest of the animal kingdom, to make animal products with a high nutritionnal value such as milk and meat. They do not compete with humans or other animals for the use of feed. This is due to the presence of forestomachs in ruminants, harbouring a dense and diverse microbial population, since the animals do not produce endogenous enzymes able to degrade plant biomass.
Of the forestomachs, the rumen represents the larger fermentation chamber where ingested feed is stored to be degraded by anaerobic protozoa, bacteria and fungi. Among this microbial population, protozoa are considered non essential since ruminants will survive well after protozoa have been removed (defaunation). However, many studies carried out during the last two decades showed that protozoa play an important role in the ruminal digestive processes. They actively degrade plant cell wall and can stimulate the cellulolytic activity of bacteria [2]. They use for their own nutritional purpose both the dietary proteins and bacterial proteins and most of their own proteins are recycled in the rumen, which, as a consequence, decreases in the intestinal supply of amino acids for ruminants and increases the urinary excretion of nitrogen as urea [1]. They also alter the composition of VFAs produced during ruminal fermentations and alter the supply of energy to the animals. More propionate is generated at the expense of acetate and butyrate when protozoa are eliminated [3]. Also, methane production is decreased in defaunated animals [4].
These aspects are discussed to characterize the nature of the relationships between ruminants and rumen ciliate protozoa.
[1] Jouany J.P. (1996) Effect of rumen protozoa on nitrogen utilization by ruminants. J. Nutr. 126: 1335S-1346S
[2] Jouany J.P. and Martin C. (1997) Effect of protozoa in plant cell wall and starch digestion in the rumen, in "Rumen Microbes and Digestive Physiology in Ruminants", ONODERA R. et al. Eds, Japan Sci., Soc. Press, Tokyo/S Karger, Busel, pp 11-24
[3] Jouany J.P., Demeyer D.I., Grain J. (1988) Effect of defaunating the rumen. Anim. Feed Sci. Technol. 21: 229-263
[4] Newbold C.J., Lassalas B., Jouany J.P. (1995) The importance of methanogens associated with ciliate protozoa in ruminal methane production in vitro. Lett. Appl. Microbiol. 21: 230-234
| LOCATION |
DATE |
TIME |
| Lecture Hall I |
Thursday, April 9 |
08:30 am |