Toward a new practical energy evaluation system for dairy cows.

Area of Science:

• Animal Nutrition
• Dairy Science
• Energy Metabolism

Background:

• Energy evaluation systems are crucial for translating animal net energy (NE) requirements into metabolisable energy requirements (MER).
• Previous systems often depended on feed quality, complicating accurate MER prediction for dairy cows.
• The Feed into Milk (FiM) and Tolkamp and Ketelaars (T&K) systems offer feed-quality independent approaches to MER prediction.

Purpose of the Study:

• To analyze the parameter contributions and differences in MER predictions between the FiM and T&K energy evaluation systems.
• To identify the underlying causes for discrepancies in MER predictions between the two systems.
• To evaluate the FiM system's parameter requirements and internal consistency.

Main Methods:

• Comparative analysis of the FiM and T&K energy evaluation systems for dairy cows.
• Examination of the role of individual parameters in MER prediction within the FiM system.
• Assessment of differences in net energy for maintenance and metabolisable energy utilization efficiency assumptions.

Main Results:

• The FiM system requires nine parameters, while the T&K system uses only two, yet MER predictions are similar (±2%) for milk yields between 10-40 kg.
• Significant differences exist in NE for maintenance and partial efficiency of ME utilization for lactation between the systems.
• FiM predictions are higher than T&K for very low and very high milk yields; FiM exhibits internal inconsistencies.

Conclusions:

• The FiM system can be simplified by reducing parameter requirements with minimal impact on MER predictions.
• The T&K system is simpler but could be improved with updated parameter estimations.
• The FiM system's curvilinear model and high maintenance NE parameter contribute to internal inconsistencies.