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

Residual feed intake (RFI) is an efficiency trait underpinning profitability and environmental sustainability in dairy production. This study compared performance during a complete lactation of 36 multiparous dairy cows divided into three equal-sized groups with high (HRFI), intermediate (IRFI) or low RFI (LRFI). Residual feed intake was determined by two different equations. Residual feed intake according to the NorFor system was calculated as (RFI(NorFor)) = (NE(intake))–(NE(maintenance) + NE(gestation) + NE(milk)—NE(mobilisation) + NE(deposition)). Residual feed intake according to the USA National Research Council (NRC) (RFI(NRC)) was calculated as: RFI = DMI − predicted DMI where predicted(s) DMI = [(0.372× ECM)+(0.0968×BW(0.75))]×(1−e(−0.192×(DIM/7+3.67))). Cows in the HRFI(NorFor) group showed higher daily CH(4) production, CH(4)/ECM and CH(4) yield (g/kg DMI) than IRFI(NorFor) and LRFI(NorFor) cows. Cows characterized by high efficiency (LRFI(NorFor)) according to the NorFor system had lower body weight. Dry matter intake and apparent dry matter digestibility were not affected by efficiency group but milk yield was lower in the low efficiency, HRFI(NorFor,) group. Cows characterized by high efficiency according to the NRC system (LRFI(NRC)) had lower dry matter intake while yield of CH(4) was higher. Daily CH(4) production and CH(4) g/kg ECM did not differ between RFI(NRC) groups. Dairy cows characterized by high efficiency (both LRFI(NorFor) and LRFI(NRC) cows) over a complete lactation mobilized more of their body reserves in early lactation as well as during the complete lactation. The results also indicated great phenotypic variation in RFI between different stages the lactation.