Abstract:
Effects of protozoa on the outflow of long chain fatty acids from the rumen Damry and R.S. Hegarty 1 2 `Department of Animal Science, University of New England, Armidale NSW 2351 *NSW Agriculture Beef Centre, University of New England, Armidale NSW 2351 The decrease in amino acid outflow from the rumen caused by the presence of protozoa has been well documented (Ivan et al. 199 1). In contrast, no comparison has been made of the ruminal outflow of long chain fatty acids (LCFA) Tom animals with or without rumen protozoa. Katz and Keeney (1967) reported up to 75% of LCFA in the rumen is present in protozoa and, unlike amino acids, it is known that LCFA are not degraded in the rumen. Because microbial LCFA may provide an important energy source for the ruminant, a study ofthe outflow of CFA from the rumen of sheep with or without rumen protozoa was made. Seven sheep cannulated in the rumen and abomasum were defaunated using alkanate 3 SL3. Three sheep were refaunated with mixed rumen fluid and had a mean protozoa1 population of 7.5 x 1 O5 cells/mL at the time of study. The diet (400 g lucerne chaff, 400 g oaten chaff) was provided in equal portions at hourly intervals. The flow of digesta was measured using endogenous plant hentriacontane (C3 1; 100% recovery through rumen assumed) and CrEDTA as markers (Table 1). LCFA content of the diet and digesta was measured by the method of Viviani et al. (1966). Ruminal LCFA production (g/d) was estimated as the difference between LCFA intake and LCFA flow through the abomasum. The presence of protozoa in the rumen did not cause a significant change in the apparent digestibility of dry matter in the rumen, the total outflow of lipid fi-om the rumen or the synthesis of lipid within the rumen. The consistency of ruminal lipid synthesis across treatments indicates that the quantity of lipid synthesised by the microbes, which replace protozoa after defaunation, equals that produced by protozoa in untreated sheep. It is concluded that elimination of rumen protozoa is unlikely to affect the total LCFA available to the ruminant. References Ivan, M., Hidiroglou, M. and Petit H.V. (1991). Duodenal flow of nitrogen following protozoal inoculation of fauna-free sheep fed a diet supplemented with casein or soybean meal. Canadian Journal ofAnimal Science 71,793-80 1. Viviani, R., Gondolfi, MG and Rosa di Michele, S. (1966). Non-esterified, esterified and bound long chain fatty acids in rumen liquor of the sheep. Zentralblatt. Fuer: Veterinaermedizin Reihe 13, 385-391. Katz, I. and Keeney M. (1967). The lipids of some rumen holotrich protozoa. Biochimica and Biophysics Acta 144, 102-l 12. Table 1 The apparent dry matter digestibility (ADMD) and synthesis and outflow of long chain fatty acids (LCFA) from the rumen of sheep with or without rumen protozoa (s.d. in parenthesis). Recent Advances in Animal Nutn'tion in Australia 1997 University of New England, Annidale NSW 2351, Australia