Nitrogen Utilization and Ruminal Microbiota of Hu Lambs in Response to Varying Dietary Metabolizable Protein Levels

Abstract

Optimizing the metabolizable protein level in ruminant diets represents a promising strategy to increase nitrogen use efficiency and mitigate environmental pollution. This study explored the impacts of varying metabolizable protein (MP) levels on amino acid (AA) balance, nitrogen (N) utilization, and the ruminal microbiota in Hu lambs. Fifty-four female Hu lambs of 60 d old, with an average body weight (BW) of 18.7 ± 2.37 kg, were randomly allocated to three dietary MP groups: (1) low MP (LMP, 7.38% of DM), (2) moderate MP (MMP, 8.66% of DM), and (3) high MP (HMP, 9.93% of DM). Three lambs with similar BW within each group were housed together in a single pen, serving as one experimental replicate (n = 6). The feeding trial lasted for 60 days with 10 days for adaptation. The final BW of lambs in the MMP and HMP groups increased (p p p p p p p Candidatus_Saccharimonas, Ruminococcus, and Oscillospira were the lowest (p Terrisporobacter and the Christensenellaceae_R-7_group were the highest (p Christensenellaceae_R-7_group.

Keywords

• amino acid balance
• metabolizable protein optimization
• growth performance
• nitrogen retention efficiency
• rumen bacteria