Tg. Nagaraja et al., RESPONSES IN CILIATED PROTOZOA AND RUMEN FERMENTATION IN SHEEP SUPPLEMENTED WITH BARLEY PLUS VIRGINIAMYCIN, Australian Journal of Agricultural Research, 46(6), 1995, pp. 1137-1147
An experiment was conducted to determine the changes in the population
of ciliate protozoa and the pattern of rumen fermentation in sheep fe
d a supplement of barley grain on its own or containing virginiamycin.
There were three treatment groups with a total of 25 sheep housed in
individual pens. All animals were fed chaffed wheaten hay to a maximum
of 1.4 kg head(-1) day(-1). One group received no grain supplement (n
= 5), one barley grain (n = 10) and the third barley plus virginiamyc
in (40 g/t grain; n = 10). The amount of grain was gradually increased
over a period of 5 days to a maximum of 700 g of barley or barley plu
s virginiamycin on day 5. Grain (700 g/head) was then fed twice weekly
for a further 18 days. Samples of rumen fluid were taken on days 1, 2
, 3, 5, 6, 9*, 12*, 23* and 24 (* signifies days when 700 g barley wa
s fed). In sheep supplemented with barley the population density of ci
liate protozoa was increased (P < 0.01) from day 3 of the 5 day introd
uction to grain (approximately 170 x 10(4) protozoa/ml at day 5), but
the increase was not sustained when grain was fed at intervals of 3 or
4 days. In sheep supplemented with barley plus virginiamycin, the pop
ulation density of ciliate protozoa was increased significantly (P < 0
.01) only at days 5 and 6 of the experiment (approximately 100 x 10(4)
protozoa/ml at day 5). Sheep supplemented with barley plus virginiamy
cin at day 5 had a higher concentration of L-lactate (P < 0.05) at 6 a
nd 12 h and propionate (P < 0.05) at 6, 9, 12 and 24 h than sheep supp
lemented with barley alone. It was concluded that virginiamycin was in
hibitory to protozoa during the introduction to grain, and L-lactate a
ccumulation in the rumen of sheep supplemented with barley plus virgin
iamycin may be a result of altered fermentation associated with reduce
d numbers of protozoa.