Differential Colonization of Plant Parts by the Rumen Microbiota is likely to be due to Different Forage Chemistries

Sharon A Huws

doi:10.4172/1948-5948.1000126

Abstract

In this experiment we investigated the hypothesis that heterogeneity of plant structures presents disparity in niches available for colonisation by the rumen microbiota resulting in differential colonisation. Fresh perennial ryegrass (PRG) stem and leaves were incubated in the presence of rumen bacteria under rumen-like conditions with incubations harvested at many time intervals up to 24 h. In vitro dry matter degradability (IVDMD) of stem material was lower than that of leaves at all harvesting times. Denaturing Gradient Gel Electrophoresis (DGGE) derived dendrograms, canonical analysis of principal coordinates (CAP) and PERMANOVA demonstrated that diversity of bacteria attached to PRG stem and leaf material was different at all harvesting times although QPCR data showed similar quantities of bacterial 16S rDNA on stem and leaf material at all harvesting times. Conversely, bacterial diversity on abaxial and adaxial leaf surfaces was similar, but 16S rDNA quantity differed with more 16S rDNA on the adaxial surface at all harvesting times. Image analysis of low temperature scanning electron microscopy (LTSEM) pictures confirmed that biofilm coverage on the adaxial surface was greater than the abaxial surface. We demonstrate that differing plant parts can affect attached bacterial diversity and/or 16S rDNA quantity present. This result is consistent with concepts of niche specialisation by the rumen microbiota. This observation is particularly relevant to understanding rumen plant-microbe interactions which is necessary for development of novel strategies for improving ruminant nutrient use efficiency.

Highlights

With an ever increasing population and increased demands for ruminant products, the need to ensure future food security is paramount [1]
Chemical compositional differences were found between stem and leaf in terms total nitrogen, water soluble carbohydrate (WSC) neutral-detergent fibre (NDF), acid-detergent lignin (ADL), and alkanes/lipid content (Table 1)
Leaf material was degraded to a greater extent than stem material with 69.2 and 58.9% being degraded for leaf and stem material respectively after 24 h incubation (Table 2)

Summary

Introduction

With an ever increasing population and increased demands for ruminant products, the need to ensure future food security is paramount [1] This presents a major challenge to find novel strategies to sustainably increase animal productivity. Furthering our understanding of plant-microbe interactions during colonisation and plant degradation is expected to offer novel opportunities to improve ruminant nutrient use efficiency in order to sustainably increase meat and milk availability. Rumen microorganisms colonising the surfaces of forages are confronted with highly variable physiochemical conditions including nutrient type and availability due to the heterogeneity of the plant material. This heterogeneity may affect microbial attachment and subsequent biofilm formation. Bacterial attachment to different parts of the plant material may be different due to the differences in their surface chemistry

Methods

Results

Conclusion