# Metabolomic Profiling of Serum Reveals Energy Metabolism Differences in Nellore Bulls with Divergent Growth Rates during Feedlot Finishing

## TL;DR

This study found that Nellore bulls with higher growth rates have distinct serum metabolite profiles linked to better energy metabolism.

## Contribution

The study identifies specific metabolites and pathways associated with divergent growth rates in beef cattle during feedlot finishing.

## Key findings

- HP cattle had higher levels of threonine, glycolate, ornithine, histidine, and creatinine.
- LP cattle showed elevated phenylalanine, succinate, acetate, asparagine, and 2-hydroxyisobutyrate.
- Key pathways like mitochondrial electron transport and threonine degradation were enriched in HP animals.

## Abstract

This study aimed to identify and quantify serum metabolites
in
beef cattle exhibiting different growth rates during the finishing
phase. A total of 120 Nellore (Bos indicus) bulls, averaging 387 ± 14 kg in body weight and 24 ±
2 months of age, were evaluated. The animals were housed for 115 days,
and on day 21 (end of the first adaptation step), blood samples were
collected from the coccygeal vein for metabolomic analysis. Based
on average daily gain (ADG), two contrasting groups were selected:
high performance (HP; n = 12) and low performance
(LP; n = 12). Serum samples collected on day 21 were
analyzed by proton nuclear magnetic resonance (1H NMR)
to extract and quantify metabolites. Longissimus muscle area (LMA),
backfat thickness (BFT), and hot carcass weight (HCW) were measured
via ultrasound at the end of the finishing period. Animal performance
was affected by growth rate, with HP animals showing significantly
greater final body weight, HCW, and BFT (p < 0.05).
A total of 47 serum metabolites were identified, including essential
and nonessential amino acids, sugars, peptides, vitamins, amino acid
derivatives, and organic acids. HP cattle exhibited higher concentrations
of threonine, glycolate, ornithine, histidine, and creatinine (p < 0.05), while LP animals showed greater levels of
phenylalanine, succinate, acetate, asparagine, and 2-hydroxyisobutyrate
(p < 0.05). Key enriched pathways included the
mitochondrial electron transport chain (p = 0.06),
ethanol degradation (p = 0.08), and threonine and
2-oxobutanoate degradation (p = 0.09). These findings
suggest enhanced energy metabolism in HP animals, driven by greater
substrate diversity, while LP animals may exhibit impaired mitochondrial
function, negatively impacting performance.