Effects of the dietary Enterolobium cyclocarpum foliage on the population dynamics of rumen ciliate protozoa in sheep

The antiprotozoal activity of Enterolobium cyclocarpum foliage was tested in the present study in in vitro, using a technique that measures the breakdown of [C-14]-labelled Selenomonas ruminantium, and in vivo experiments. In vivo, the activity was measured in two experiments with rumen cannulated sheep fed a diet based on barley silage and barley grain. Rumen fluid samples were collected and used in both experiments for enumeration of protozoa and analysis of rumen fermentation parameters. The in vitro assay showed a 20-95% decrease in the rate of breakdown of [C-14]-labelled S. ruminantium by protozoa with increased amounts of E. cyclocarpum in the incubation media, ranging from 0.5 to 10, 1(-1). The results of the first in vivo experiment with sheep showed that the E. cyclocarpum supplement reduced (P < 0.05) protozoal numbers during days 4-11 (by 49-75%), but the numbers gradually increased to the level of the control group by day 20. The reduction in the protozoal population was associated with a reduced (P < 0.1) concentration of ammonia-N in rumen fluid. pH and volatile fatty acid (VFA) concentrations were not affected by the treatment (P > 0.05). The results of the second experiment showed that compared to day -1, there were reduced (P < 0.05) protozoa concentrations in rumen fluid on almost all days during Period 1, but protozoa were reduced (P < 0.05) only on days 6, 8 and 21 in Period 3. Comparison of Periods 1 and 3 resulted in lower (P < 0.05) protozoal concentration means in Period I on days 3-6, but the rest of the days were not different (P > 0.05). It was concluded that the antiprotozoal effect of the E. cyclocarpum foliage supplement was only transitory and effective only the first time it was fed to the same animals. (C) 2003 Elsevier B.V. All rights reserved.