Quantification by real-time PCR of cellulolytic bacteria in the rumen of sheep after supplementation of a forage diet with readily fermentable carbohydrates: effect of a yeast additive.
OBJECTIVE
To examine the effect of concentrate and yeast additive on the number of cellulolytic bacteria in the rumen of sheep.


RESULTS
Fibrobacter succinogenes, Ruminococcus albus and Ruminococcus flavefaciens were quantified using real-time PCR (targeting 16S rDNA) in parallel to cellulolytic flora enumeration with cultural techniques. Whatever the conditions tested, R. flavefaciens was slightly more abundant than F. succinogenes, with both species outnumbering R. albus. Before feeding, the shift from hay to hay plus concentrate diet had no effect on rumen pH and on the number of the three specie; while after feeding, the concentrate-supplemented diet induced a decrease (-1 log) of the number of the three species concomitant with the rumen acidification. Overall, the presence of the live yeast resulted in a significant increase (two- to fourfold) of the Ruminococci.


CONCLUSIONS
The use of real-time PCR allowed us to show changes in the number of cellulolytic bacterial species in vivo in response to diet shift and additives that could not be as easily evidenced by classical microbial methods.


CONCLUSIONS
This study contributes to the understanding of the negative impact of readily fermentable carbohydrates on rumen cellulolysis and the beneficial effect of yeast on rumen fermentation.
INRA, UR454 Unité de Microbiologie, Saint-Genès-Champanelle, France. pmosoni@clermont.inra.fr
P
P
Mosoni
F
F
Chaucheyras-Durand
C
C
Béra-Maillet
E
E
Forano
D000821:Animal Feed; D000818:Animals; D050260:Carbohydrate Metabolism; D002482:Cellulose / Q000378:metabolism*; D015169:Colony Count, Microbial; D004269:DNA, Bacterial / Q000032:analysis; D019587:Dietary Supplements; D005285:Fermentation; D045848:Fibrobacter / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D006094:Gram-Positive Bacteria / Q000302:isolation & purification* / Q000378:metabolism; D008297:Male; D015345:Oligonucleotide Probes / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D012417:Rumen / Q000378:metabolism / Q000382:microbiology*; D045857:Ruminococcus / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D034561:Sheep, Domestic / Q000378:metabolism / Q000382:microbiology*; D015003:Yeasts
D004269:DNA, Bacterial; D015345:Oligonucleotide Probes; D002482:Cellulose