Effect of hay particle size and concentrate level on the main cellulolytic bacteria in the rumen of dairy cows.

Publication Type

Contribution to conference

Authors

Ölschläger, V., Weber, I., Vahjen, W., H. Tafaj, M., Simon, O. and Drochner, W.

Year of publication

2006

Published in

Proc. Soc. Nutr. Physiol

Editor

Holger Martens (Hrsg.)

Series/labeling

Berichte der Gesellschaft für Ernährungsphysiologie

Page (from - to)

147

Conference location

Göttingen

Conference date

21.-23.03.2006

Keywords

dairy cows, hay particle size, rumen

Efficient fiber digestion is especially important for high-performance dairy cows in feeding strategies that also aim at animal welfare. High levels of concentrate in diets for lactating cows limit the sufficient supply of structural fiber and may restrict uptake of roughage with consequent interference of physiological functions such as ruminal pH-regulation and passage rate. It is known that feed particle size and concentrate level play an essential role in digestion and composition of rumen contents in different layers of the rumen. Since digestion of structural fiber in the rumen is carried out by cellulolytic bacteria, the aim of this study was to investigate the changes in cell numbers of the main cellulolytic bacteria in the rumen as well as associated enzyme activities and several key bacterial metabolic parameters. Results: R. albus cell counts were enhanced by long-, as compared to short hay particle size, but different concentrate levels had no effect on R. albus. R. flavefaciens displayed a similar growth pattern as R. albus in the liquid phase. In the solid phase, R. flavefaciens cell counts were reduced after feeding, while R. albus cell counts increased. Cell counts of F. succinogenes were not influenced by diet type. The ratio of F. succinogenes to total eubacterial cell counts was higher in the liquid phase. High concentrate always led to a 0.5 to 1 log unit increase in eubacterial cell counts. Hay particle length as well as dosage of concentrate had an influence on the ratio of cellulolytic bacteria to total bacteria (tab. 1) and correlated well to volatile fatty acid concentrations in the rumen. As expected, structural carbohydrate degrading enzymes increased with diets containing long hay particles. Preliminary DGGE results did not indicate significant qualitative changes in the eubacterial composition. Conclusions: The present study indicates that ruminal bacteria with non structural carbohydrate enzyme activities benefit from carbohydrates in