Full-lactation performance of multiparous dairy cows with differing residual feed intake

Area of Science:

• Animal Science
• Nutritional Physiology
• Environmental Sustainability

Background:

• Residual feed intake (RFI) is a key trait for dairy production efficiency, profitability, and environmental impact.
• Understanding RFI variations is crucial for optimizing dairy farming practices and reducing greenhouse gas emissions.

Purpose of the Study:

• To compare dairy cow performance and methane (CH4) emissions based on residual feed intake (RFI) classifications.
• To evaluate the impact of two different RFI calculation systems (NorFor and NRC) on cow performance and CH4 output.

Main Methods:

• Thirty-six multiparous dairy cows were grouped into high, intermediate, and low RFI categories based on NorFor and NRC equations.
• Performance traits, including dry matter intake (DMI), milk yield, body weight, and CH4 production, were monitored throughout a complete lactation.

Main Results:

• High RFI (low efficiency) cows, particularly under the NorFor system, exhibited higher daily CH4 production and CH4 yield (g/kg DMI).
• High efficiency cows (low RFI) under both systems mobilized more body reserves, especially in early lactation.
• Milk yield was lower in low efficiency (high RFI) cows using the NorFor system, while NRC-defined high efficiency cows had lower DMI.

Conclusions:

• Dairy cow efficiency, as measured by RFI, significantly influences CH4 emissions and body reserve dynamics.
• The choice of RFI calculation system (NorFor vs. NRC) can affect the interpretation of cow performance and environmental impact.
• High efficiency dairy cows mobilize greater body reserves, highlighting the trade-offs between feed efficiency and energy partitioning.