Oscillating dietary crude protein concentrations increase N retention of calves by affecting urea-N recycling and nitrogen metabolism of rumen bacteria and epithelium

PLoS One. 2021 Sep 10;16(9):e0257417. doi: 10.1371/journal.pone.0257417. eCollection 2021.

Abstract

The purpose of this study was to investigate the effects of oscillating crude protein (CP) concentration diet on the nitrogen utilization efficiency (NUE) of calves and determine its mechanism. Twelve Holstein calves were assigned randomly into static protein diet (SP, 149 g/kg CP) and oscillating protein diet (OP, 125 and 173 g/kg CP diets oscillated at 2-d intervals) groups. After 60 days of feeding, the weights of total stomach, rumen and omasum tended to increase in calves fed OP. The apparent crude fat digestibility, NUE and energy metabolism also increased. In terms of urea-N kinetics evaluated by urea-15N15N isotope labeling method, the urea-N production and that entry to gastrointestinal tended to increase, and urea-N reused for anabolism increased significantly in calves fed OP during the low protein phase. These data indicate that urea-N recycling contributed to improving NUE when dietary protein concentration was low. In addition, the differentially expressed genes in rumen epithelium and the rumen bacteria involved in protein and energy metabolism promoted the utilization of dietary protein in calves fed OP.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animal Feed / analysis
  • Animals
  • Bacteria
  • Biodiversity
  • Cattle
  • Diet / veterinary
  • Dietary Proteins / metabolism
  • Epithelium / metabolism
  • Epithelium / microbiology*
  • Gene Expression Profiling
  • Kinetics
  • Liver / metabolism
  • Male
  • Metabolomics
  • Nitrogen / metabolism*
  • Oscillometry
  • RNA, Ribosomal, 16S / metabolism
  • Rumen
  • Transcriptome
  • Urea / chemistry*

Substances

  • Dietary Proteins
  • RNA, Ribosomal, 16S
  • Urea
  • Nitrogen

Grants and funding

TG received funding from the China Agriculture Research System (grant number CARS-36). HL received funding from the National Natural Science Foundation of China (grant number 31702138). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.