With the objective to evaluate the modulator effect of
Leucaena leucocephala
on the methanogenic bacteria and
other microbial groups in the rumen was conducted a trial according to a completely randomized design in a
factorial arrangement (4 x 4, four leucaena proportions and four times of fermentation), under
in vitro conditions.
The trial consisted of four star grass (
Cynodon nlenfuensis
) with leucaena ratios, which were: treatment A=100:0,
B=80:20, C=75:25, and D=70:30. The sampling was performed before the incubation (0 hour), and at 4, 8, and
12 h of fermentation. The counts of methanogenic bacteria were 40.22, 38.42, 13.98, and 12.46 x 10
7 cfu/mL
for the treatments A, B, C, and D, respectively. The modulator increased the population of cellulolytic bacteria,
compared with the control without supplement, and the best response was found in the ratios 80:20 and 70:30.
The populations of cellulolytic fungi were 2.08, 3.49, 3.69, and 4.48 x 10
3 tfu/mL for A, B, C, and D treatments,
respectively. The protoozoa population varied from 1.50 to 2.75 x 10
5 cell/mL, under the trial conditions. In all
cases with
L. leucocephala as modulator the populations were significantly small, but the smallest was found
when the ratio 80:20 of star grass:modulator was used. It is concluded that the modulator from the fermentation
with
L. leucocephala is suitable for reducing the population of rumen methanogenic bacteria without affecting
the total population of cellulolytic bacteria
