Semester

Summer

Date of Graduation

2023

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Animal and Nutritional Sciences

Committee Chair

Ibukun Ogunade

Committee Member

Scott Bowdridge

Committee Member

Crystal Smith

Abstract

Cattle production is one of the most important agricultural industries in the United States. Despite its overall production efficiency, the industry is facing considerable adversities to its long-term sustainability due to population growth, decreased land availability, and the increase in global warming. Since feed efficiency imposes an immense influence on the cost of production for animals and is a major cost determinant for profitability, the improvement of feed utilization through the understanding of animal-to-animal variation in feed efficiency is pertinent to increase farm productivity and profitability. Residual feed intake (RFI) is a measure of feed efficiency and is defined as the difference between the actual and predicted feed intake of an animal, with consideration of variation in body size and growth performance. The objective of this study was to analyze rumen and urine metabolome to identify metabolite biomarkers and biochemical pathways associated with divergent RFI phenotype in crossbred beef steers. A group of 56 crossbred growing beef steers (average BW= 261± 18.5 kg) were adapted to a high-forage total mixed ration in a confinement dry lot equipped with GrowSafe intake nodes for a period of 49 d to determine their residual feed intake classification (RFI). After RFI determination, weekly urine samples were collected three times from beef steers with negative RFI (most efficient (HFE); RFI = - 1.93 kg/d, n = 8) and positive RFI (least efficient (LFE); RFI = + 2.01 kg/d, n = 8). Urine samples collected were then composited for each steer. Rumen fluid samples were collected weekly for three weeks from beef steers with negative RFI (most efficient (HFE; RFI=-1.93 kg/d, n=7) and positive RFI (least efficient (LFE); RFI= +2.01 kg/d, n=7). Metabolome analysis was conducted using a chemical isotope labeling/liquid chromatography-mass spectrometry, specifically analyzing metabolites containing anime/phenol-chemical groups, which are metabolites involved in the metabolism of amino acids. A total number of 443 amine/phenol-containing metabolites were detected and identified in rumen fluid, while a total number of 557 amine/phenol-containing metabolites were detected and identified in urine. Biomarker analysis of the rumen amine/phenol-metabolome identified isomer of cadaverine, baeocystin, 6-methyladenine, N(6)-methyllysine as candidate biomarkers of RFI (false discovery rate ≤ 0.05; Area Under the Curve ≥ 0.70). Biomarker analysis of the urinary amine/phenol-metabolome identified N-acetyl-L-tyrosine, O-methyl-L-threonine, uridine, and threoninyl-hydroxyproline as candidate biomarkers of RFI (false discovery rate ≤ 0.05; Area Under the Curve ≥ 0.85). In conclusion, the results of our study revealed that alterations in rumen fluid and urine amine/phenol-metabolome are associated with divergent RFI phenotype and both rumen fluid and urine are potential sources of candidate metabolite biomarkers associated with RFI in beef cattle.

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