The Impact of Pre-Slaughter Fasting on the Ruminal Microbial Population of Commercial Angus Steers.

Christina Breanne Welch,Todd R Callaway,Jeferson M Lourenco,T Dean Pringle,Taylor Rae Krause,Darren S Seidel,Michael J Rothrock

doi:10.3390/microorganisms9122625

Christina Breanne Welch, Todd R Callaway + Show 5 more

Open Access

https://doi.org/10.3390/microorganisms9122625

Copy DOI

Abstract

Diet impacts the composition of the ruminal microbiota; however, prior to slaughter, cattle are fasted, which may change the ruminal microbial ecosystem structure and lead to dysbiosis. The objective of this study was to determine changes occurring in the rumen after pre-slaughter fasting, which can allow harmful pathogens an opportunity to establish in the rumen. Ruminal samples were collected before and after pre-slaughter fasting from seventeen commercial Angus steers. DNA extraction and 16S rRNA gene sequencing were performed to determine the ruminal microbiota, as well as volatile fatty acid (VFA) concentrations. Microbial richness (Chao 1 index), evenness, and Shannon diversity index all increased after fasting (p ≤ 0.040). During fasting, the two predominant families Prevotellaceae and Ruminococcaceae decreased (p ≤ 0.029), whereas the remaining minor families increased (p < 0.001). Fasting increased Blautia and Methanosphaera (p ≤ 0.003), while Campylobacter and Treponema tended to increase (p ≤ 0.086). Butyrate concentration tended to decrease (p = 0.068) after fasting. The present findings support that fasting causes ruminal nutrient depletion resulting in dysbiosis, allowing opportunistic pathogens to exploit the void in the ruminal ecological niche.

Highlights

Diet is one of the main driving forces of the microbial composition within the rumen [1,2,3], and the microbes best able to utilize dietary nutrients have a competitive advantage
Pre-slaughter fasting dramatically impacted the overall alpha-diversities of the ruminal microbial ecosystem (Table 1)
For the high-residual feed intake (RFI) steers, there was an increase in bacterial richness (Chao 1; p = 0.001), evenness (p = 0.040), and diversity (Shannon index; p = 0.001) in the rumen samples collected at lairage compared to those at slaughter

Summary

Introduction

Diet is one of the main driving forces of the microbial composition within the rumen [1,2,3], and the microbes best able to utilize dietary nutrients have a competitive advantage. Throughout the production cycle, ruminal nutrient concentrations derived from the diet drive selective pressures on the microbial population; cattle are often fasted for 24–36 h prior to slaughter (i.e., lairage). The ruminal microbial population depletes the rumen of available nutrients, altering or removing the selective pressures on the rumen microbial ecosystem. Removing selective pressure can lead to a destabilization of the microbial population, or a dysbiosis, that allows opportunistic pathogens a chance to increase their populations in the rumen. Fasting cattle reduces gastrointestinal concentrations of volatile fatty acids (VFA), which inhibit ruminal populations of Salmonella and E. coli [8]; fasting allows foodborne pathogenic bacteria to increase their

Objectives

Methods

Results

Discussion

Conclusion