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Table 3 Rumen pH, volatile fatty acids (VFA), and apparent digestibility 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
pH 6.41 6.30 0.08 0.35 0.54 0.86
Total VFA, mmol/L 101 108 3.84 0.18 0.21 0.22
Molar proportion, mmol/100 mmol
 Acetate (A) 65.1 64.2 0.86 0.46 0.28 0.61
 Propionate (P) 20.2 21.5 0.94 0.36 0.08 0.40
 Butyrate 11.1 10.8 0.39 0.71 0.17 0.87
 Isobutyrate 0.72 0.68 0.04 0.44 < 0.01 0.43
 Valerate 1.45 1.45 0.05 0.98 < 0.01 0.30
 Isovalerate 1.45 1.30 0.08 0.21 0.06 0.71
 A: P ratio 3.29 3.11 0.18 0.46 0.07 0.40
Apparent digestibilityb
 DM, % 64.0 64.4 0.87 0.73 0.12 0.43
 CP, % 65.4 66.2 1.55 0.73 0.24 0.69
 NDF, % 35.9 35.4 1.02 0.74 0.02 0.22
 ADF, % 33.7 32.9 1.06 0.60 0.30 0.28
  1. aP value associated with RFI, time, and the interaction of RFI and time
  2. bDM dry matter, CP crude protein, NDF neutral detergent fiber, ADF acid detergent fiber