Coupling a reproductive function model to a productive function model to simulate lifetime performance in dairy cows.

Area of Science:

• Animal Science
• Dairy Cattle Physiology
• Mathematical Modeling

Background:

• Dairy cow reproductive success is crucial for lifetime performance but is challenging to predict due to complex interactions with productive functions.
• Existing models often lack integrated simulation of both productive and reproductive aspects throughout a cow's lifespan.
• Understanding these interactions is vital for improving herd fertility and overall farm profitability.

Purpose of the Study:

• To introduce and validate a dynamic, integrated model simulating the lifetime productive and reproductive performance of dairy cows.
• To couple an existing productive function model (GARUNS) with a novel reproductive function model (RFM).
• To provide a tool for evaluating factors affecting fertility at individual cow and herd levels under different management scenarios.

Main Methods:

• Developed a dynamic cow model by coupling the GARUNS (productive function) and RFM (reproductive function) models.
• RFM simulates reproductive stages (e.g., anestrous, ovulating, gestating) and hormonal profiles, influenced by GARUNS outputs (energy balance, TPEW).
• Incorporated a farming system model for diverse management protocols and conducted 10,000 simulations over a 5000-day period.

Main Results:

• Model simulations demonstrated consistency with established literature values for reproductive performance.
• The integrated model successfully simulated deviations in reproductive trajectories across physiological stages.
• Results highlight the model's capability to assess the impact of various factors on fertility.

Conclusions:

• The dynamic, integrated cow model provides a robust platform for simulating lifetime productive and reproductive performance.
• This tool enables the evaluation of genetic and management factors influencing dairy cow fertility.
• The model serves as a basis for optimizing reproductive strategies and improving dairy herd management.