Assessment of rumen microbiota in beef heifers with different feed efficiency and managed under different feeding systems

• Author / Creator

  Liu, Junhong

• The linkage between rumen microbiota and feed efficiency has been studied in cattle managed under the drylot system, especially in the feedlot with high-grain diets. However, pasture-based beef operations still dominate the beef production system around the world. In Alberta and other provinces of Canada, most cow-calf producers keep their cattle on summer pasture to lower the labor and feed costs. Similarly, backgrounding beef cattle are mainly operated under the extensive feeding system, mostly on grazing. To date, very limited studies focused on the rumen microbiota of beef cattle under grazing system. To fill this knowledge gap, the present study was performed and is presented in this thesis. This study investigated the interactions of two feeding systems (drylot vs grazing) and feed efficiency (measured with residual feed intake (RFI)) (H-RFI, n=8; L-RFI, n=8) on microbial populations and fermentation products. This study also explored whether the rumen microbiota in heifers with divergent feed efficiency have different change patterns when the feeding system changed. The results showed that the feeding system had significant effects on butyrate and isovalerate concentrations, and acetate to propionate ratio in the rumen. During the transition from drylot to grazing system, heifers with divergent RFI had different patterns of changes in microbial taxonomic compositions. For example, the relative abundance of two predominant phyla Firmicutes and Bacteroidetes were significantly increased and decreased, respectively, only in H-RFI heifers when the feeding system changed from drylot to grazing. These results suggest that these inefficient heifers had more diverse rumen microbial communities than efficient heifers. Rumen microbial functions were also predicted using PICRUSt2 package. In total, 10 major bacterial MetaCyc pathways were predicted, and 7 of them significantly increased only in the rumen of H-RFI heifers when the feeding system changed. This indicates that L-RFI (efficient) heifers have more stable rumen microbiota when the feeding system changed, which also suggests that efficient heifers may maintain their efficiency in different feeding systems through maintaining feed efficiency-related microbes and microbial metabolic pathways. This work provides fundamental knowledge to help to understand the rumen microbiota of cattle under different feeding systems and support the development of potential methods to manipulate rumen microbiota to improve the feed efficiency of beef cattle under grazing.

• Subjects / Keywords

  • Feed efficiency
  • Cattle
  • Grazing
  • RFI
  • Rumen microbiota

• Graduation date

  Spring 2020

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-mdqm-p530

• License

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