Masters Theses

Date of Award

8-2023

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Science

Major Professor

Phillip R. Myer

Committee Members

Kyle McLean, Brynn Voy

Abstract

With an expected increase in population by 2050, the demand for more animal protein will increase. To improve the sustainability of US cattle production, producers and researchers have historically focused on improving the feed efficiency of steers, producing a more marketable beef product. However, without a successful pregnancy, there would be no marketable animal to feed. The objective of this study was to examine the physiological changes that occur during pregnancy and their impact on the rumen microbial communities and the correlation to feed efficiency status in Angus heifers. Utilizing 17 cannulated Angus heifers, feed efficiency data was previously collected by utilizing a GrowSafe to monitor feed intake for a 70d trial period to calculate residual feed intake. Following the trial, heifers were bred, and rumen fluid and content samples were collected every two weeks during gestation and four samples were collected after parturition. A total of 30-40mL of rumen fluid was collected during each sampling and rumen solid material was removed from the ventral sac. To analyze the microbial communities, DNA was extracted from the rumen samples, sequencing libraries were prepared targeting the bacterial 16S rRNA gene and was sequenced using an Illumina MiSeq. All microbial analyses were analyzed in the R environment where alpha diversity, beta diversity, and relative abundances were calculated. Metabolite analysis was performed using ultra high performance liquid chromatography high resolution mass spectrometry, and Metabolomic Analysis and Visualization Engine (MAVEN) was used for metabolite identification. Downstream analysis including the “ANCOMBC” package, with a focus on the global results, indicated 10 ASVs, all Prevotella or Succiniclasticum at the genus level, with significant changes across time points. Based on a one-way ANOVA, 90 metabolites were determined significant throughout pregnancy. The 10 metabolites with the highest variable importance of projection (VIP) scores were used for correlation calculations. Of the 10 ASVs and 10 metabolites, significant correlations with feed efficiency status were found at various time points when P<0.05. The he rumen microbiome at various time points during pregnancy could indicate feed efficiency status, but further research is necessary to continue to improve the cow calf enterprise.

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