Impact of Feed Efficiency and Diet on Adaptive Variations in the Bacterial Community in the Rumen Fluid of Cattle

Abstract

Limited knowledge of the structure and activities of the ruminal bacterial community prevents the understanding of the effect of population dynamics on functional bacterial groups and on host productivity. This study aimed to identify particular bacteria associated with host feed efficiency in steers with differing diets and residual feed intake (RFI) using culture-independent methods: PCR-denaturing gradient gel electrophoresis (DGGE) and quantitative real-time PCR analysis. PCR-DGGE profiles were generated from the ruminal fluid of 55 steers fed a low-energy-density diet and then switched to a high-energy-density diet. Bacterial profile comparisons by multivariate statistical analysis showed a trend only for RFI-related clusters on the high-energy diet. When steers (n ‫؍‬ 19) belonging to the same RFI group under both diets were used to identify specific bacterial phylotypes related to feed efficiency traits, correlations were detected between dry matter intake, average daily gain, and copy numbers of the 16S rRNA gene of Succinivibrio sp. in low-RFI (efficient) steers, whereas correlations between Robinsoniella sp. and RFI (P < 0.05) were observed for high-RFI (inefficient) animals. Eubacterium sp. differed significantly (P < 0.05) between RFI groups that were only on the high-energy diet. Our work provides a comprehensive framework to understand how particular bacterial phylotypes contribute to differences in feed efficiency and ultimately influence host productivity, which may either depend on or be independent from diet factors.T he complex symbiotic microbiota in the rumen are responsible for the breakdown of feed components, enabling ruminants to derive approximately 70% of their metabolic energy from the microbial fermentation of feedstuffs (9). Previous research has demonstrated that many factors influence the composition of rumen microbiota, affecting the population of certain bacterial groups (18,22,23,43). Microbial diversity and activities have also been influenced by modifications to the diet (11, 51). Molecular techniques such as denaturing gradient gel electrophoresis (DGGE) demonstrated that changes in diet can affect microbial composition in the rumen (20,32,42). However, some studies have reported significant bacterial diversity among individuals (13,28). Because individuals may respond differently to diet changes, identifying relationships between the differences in bacterial diversity in the rumen and host's phenotypic variations is particularly challenging, Moreover, the effect of bacterial population dynamics on host productivity characteristics, such as feed efficiency, has not been well established.The adaptability and structural complexity of the microbial community within the ruminal ecosystem allow ruminant animals to consume a wide variety of feedstuffs (33). The type and amount of feedstuffs consumed by the host affect the nutritional supply to ruminal microbes and the end products synthesized, thereby influencing the nutrients absorbed by the host. Animals with poor feed efficienc...

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