PhenoBR: a model to phenotype body condition dynamics in meat sheep

Area of Science:

• Animal Science
• Quantitative Biology
• Ruminant Physiology

Background:

• Negative energy balance (NEB) in ruminants necessitates mobilization of body energy reserves (BRs).
• Breeding for resilience requires understanding BR dynamics (mobilization and restoration).
• Body condition score (BCS) is a practical indicator, but quantitative tools for individual dynamics are lacking.

Purpose of the Study:

• To characterize body condition dynamics in meat ewes using a modeling approach.
• To quantify individual capacities for BR mobilization and accretion over productive cycles.
• To develop a tool for assessing BR dynamics in reproductive ewes.

Main Methods:

• Utilized BCS measurements from 1,478 reproductive meat ewes in extensive rangeland.
• Developed a hybrid mathematical model and web interface (PhenoBR).
• Estimated four key parameters: accretion rate (k_b), mobilization rate (k_p), mobilization onset (t_b), and duration (ΔT).

Main Results:

• The PhenoBR model successfully converged for all ewes.
• Significant inter-individual variability was observed in BR accretion/mobilization rates and mobilization period length.
• The study demonstrated the utility of combined data-driven and concept-driven models for parameter estimation.

Conclusions:

• Individual characterization of BR dynamics is feasible and valuable.
• These parameters can rank animals by efficiency in using body reserves during NEB.
• Findings support improved farmer decision-making and genetic selection for resilient animals.