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Table 6 Nitrogen output and partitioning in 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
N intake, g/d 590 644 18.6 0.06 0.01 0.92
N output, g/d
 Feces 202 218 10.3 0.31 0.77 0.64
 Urine 206 204 13.1 0.91 0.15 0.59
 Milk 175 171 8.42 0.75 < 0.01 0.59
 Retentionb 5.72 51.4 14.1 0.04 0.15 0.82
% of N intake
 Feces 34.6 33.8 1.55 0.73 0.24 0.69
 Urine 35.1 32.3 2.28 0.39 0.03 0.80
 Milk 29.7 26.5 0.89 0.02 0.22 0.71
 Retention 0.37 7.08 2.50 0.06 0.17 0.86
  1. aP value associated with RFI, time, and the interaction of RFI and time
  2. bNitrogen retention = ingested N − fecal N − urinary N − milk N