Effect of common antimicrobial agents on the function of megasphaera elsdenii ch4, a lactate utilising probiotic for ruminants

Effect of common antimicrobial agents on the growth and metabolism of
Megasphaera elsdenii NCIMB 41125, a lactate utilising probiotic for ruminants.
By J. APAJALAHTI1, P.H. HENNING2, C.H. HORN2, S. ALAJA1, and A.
KETTUNEN1. 1Alimetrics Ltd, Koskelontie 19B, FI-02920, Espoo, Finland, 2KK
Animal Nutrition, PO Box 10520, Centurion 0046, South Africa

Acute lactic acidosis is a rumen fermentation disorder characterised by lactic acid
accumulation and drop of rumen pH. Lactic acidosis can lead to seriously
compromised animal health and performance and subsequent economic losses for the
farmer. Accumulation of lactic acid can be inhibited by increasing the number and
activity of lactic acid utilising bacteria, such as Megasphaera elsdenii as we have
shown in our previous work (Kettunen et al, this symposium).
In many countries outside Europe prophylactic antibiotics are routinely used in
feeds for ruminants to shift rumen fermentation for improved performance.
Furthermore, respiratory infections and other common ruminant diseases are often
treated with therapeutic antibiotics. In this study our target was to show how the
presence of common antimicrobial products affects the growth and metabolism of the
strain NCIMB 41125 of M. elsdenii in the rumen ecosystem.
The test system was a batch fermentation model which used 1 gram of diet (50%
corn silage, 25% barley meal, 25% soy meal) and fresh inoculum from a fistulated
cow. Anaerobic incubation was continued for 9 hours at 37 °C. Gas production
kinetics, pH, short chain fatty acids, total bacteria and M. elsdenii were analysed. The
antimicrobial compounds tested were 1) a monensin based product, 2) an antibiotic
product with aureomycin + sulfamethazine, and, 3) an antibiotic product with
terramycin. The test compounds were tested at 2 levels in the presence and absence of
the strain NCIMB 41125. Titration study was carried out to choose the test compound
levels and the levels causing 10 and 30% inhibition in the total bacterial gas
production were selected.
In the absence of antimicrobials the strain NCIMB 41125 strongly reduced the
residual level of lactic acid (P < 0.0001). It also significantly stimulated overall
bacterial fermentation and caused other previously described characteristics shifts in
the rumen microbial metabolism (Kettunen et al, this symposium). As general
bacterial inhibitors the antimicrobials significantly reduced gas production, the total
yield of volatile fatty acids, lactic acid, and the general bacterial growth. However,
none of the characteristic features of the strain NCIMB 41125 inclusion were
suppressed. For example, the percent reduction of lactic acid by the M. elsdenii strain
was unaffected by the inclusion of antimicrobials. Furthermore, the quantification of
M. elsdenii showed that monensin did not affect the growth of the bacterium during
the simulation, while the therapeutic antibiotics at the high dose slightly suppressed
M. elsdenii along with all the other bacteria present.
The results of the in vitro simulation study suggest that the live fed M. elsdenii
strain NCIMB 41125 remains competitive and retains its potential to alleviate the
symptoms of lactic acidosis also in the presence of the antimicrobials tested here.

Source: http://msbiotec.com/wp-content/uploads/2012/12/Effect_of_Common_AM_Agents_on_Growth_and_Metabolism_of_M.elsdenii.pdf