Residual Feed Intake — Breeding for Efficiency Without Sacrificing Milk
Why the old feed conversion ratio is obsolete. How RFI genetics cut feed costs permanently while maintaining full production potential.
Why Feed Conversion Ratio Is Obsolete
The traditional feed conversion ratio (kg milk per kg feed) has a fundamental flaw: it doesn't account for differences in body weight, maintenance requirements, or production level. A cow that produces 20 litres on 20 kg of feed has the same FCR as a cow producing 10 litres on 10 kg, but their efficiency is completely different. Residual Feed Intake (RFI) solves this by measuring the difference between actual feed intake and predicted intake based on metabolic body weight and production.
Understanding Residual Feed Intake
RFI is the difference between a cow's actual DMI and her predicted DMI. Negative RFI cows eat less than expected without losing milk or body condition — they're genuinely more efficient. Positive RFI cows eat more than expected for their size and production — they're less efficient. The key advantage of RFI is that it's designed to be independent of production level, so you're not accidentally selecting for low-producing "efficient" cows. A negative-RFI cow maintains full production on less feed.
Genetic Selection for RFI
RFI is moderately heritable (h² = 0.21-0.40), meaning genetic selection can permanently improve herd efficiency. Lactanet's Feed Efficiency RBV explicitly targets feed intake after 60 DIM, avoiding cows that simply starve off condition early. Every 5-point bump in a sire's Feed Efficiency RBV is expected to cut daughter DMI by ~80 kg in first lactation and ~120 kg in second. Canadian Pro$, LPI, and US Net Merit all now integrate feed efficiency with real economic weighting.
On-Farm Management for RFI
For most herds, pen-level or group-level feed efficiency (energy-corrected milk per kg DMI) is the most usable day-to-day number. Track your herd's average feed efficiency monthly. A well-managed herd should achieve 1.3-1.5 kg ECM per kg DMI. Individual RFI measurement requires individual feed intake recording, which is increasingly available through smart feeders and sensor systems. Even without individual data, selecting sires with high Feed Efficiency RBVs will shift your herd over time.
RFI measures true feed efficiency independent of production level. Select sires with strong Feed Efficiency RBVs to reduce feed costs permanently. Target 1.3-1.5 kg ECM per kg DMI at the herd level.