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Table 2 Productivity of lactating cows selected for phenotypic divergence in residual feed intake (RFI)

From: Nitrogen partitioning and microbial protein synthesis in lactating dairy cows with different phenotypic residual feed intake

Items Low
RFI
High
RFI
SEM P valuea
RFI Day RFI × Day
Number, head 10 8     
Lactation performanceb
 DMI, kg/d 24.2 26.6 0.68 0.02 < 0.01 0.32
 Milk yield, kg/d 34.0 33.1 1.39 0.65 < 0.01 0.96
 Milk protein yield, kg/d 1.11 1.10 0.05 0.90 0.03 0.91
 ECM, kg/d 35.7 36.4 1.35 0.72 < 0.01 0.85
 ECM/DMI, kg/kg 1.48 1.36 0.03 < 0.01 < 0.01 0.77
 Milk/DMI, kg/kg 1.41 1.24 0.04 < 0.01 < 0.01 0.64
 RFI, kg/d −0.96 1.18 0.22 < 0.01
Milk compositionc
 Milk fat, % 3.83 4.23 0.12 0.01 0.05 0.87
 Milk protein, % 3.26 3.33 0.06 0.40 < 0.01 0.64
 Lactose, % 4.97 4.90 0.03 0.21 < 0.01 0.15
 Total solids, % 12.7 13.0 0.14 0.12 0.12 0.90
 MUN, mg/dL 12.7 13.9 0.39 0.05 < 0.01 0.62
 SCC, × 103/mL 50.5 38.7 9.46 0.39 0.33 0.46
 Days in milk 193 182 6.30 0.22
 Parity 2.70 2.50 0.22 0.56
Body weight, kg 739 737 16.7 0.96 < 0.01 0.24
Average dairy gain, kg 0.17 0.26 0.18 0.66 0.08 0.68
  1. aP value associated with RFI, time, and the interaction of RFI and time
  2. bDMI, dry matter intake; ECM (kg) = 0.3246 × milk yield (kg) + 13.86 × milk fat (kg) + 7.04 × milk protein (kg) [44]. All cows remained pregnant during the trial
  3. cMUN milk urea nitrogen, SCC somatic cell counts